Methicillin Resistant Staphylococcus Infections

What's on this Page

10 Interesting Facts of Methicillin Resistant Staphylococcus Infections

Infection with methicillin-resistant strains of staphylococci is associated with resistance to essentially all β-lactam antibiotics, thus limiting treatment choices and having significant clinical and economic implications
MRSA infections may be aggressive and invasive and cause a wide spectrum of illnesses including skin and soft tissue infection, pneumonia, endocarditis, bone and joint infections, central nervous system infections, bacteremia, and sepsis
- MRSA often is health care–associated, but distinct community-acquired strains have caused severe skin and soft tissue infections and pneumonia in persons without exposure to the health care system
- Risk factors for community-acquired MRSA infection include participation in contact sports, military service, incarceration, and injection drug use
MRSE rarely causes infection in the absence of an invasive procedure or foreign body (eg, intravascular catheter, orthopedic or cardiovascular device, cerebrospinal fluid shunt); infections tend to be more indolent and subacute
Diagnosis is established by microbiologic examination of specimens from involved site; interpretation of results can be challenging as these organisms are skin colonizers and may contaminate specimens
- Gram stain demonstration of numerous WBCs and a preponderance of gram-positive cocci in clusters supports infection due to staphylococci
- A blood culture isolate of MRSA is considered indicative of infection, not contamination, even if only 1 of several bottles is positive
- Criteria exist to aid in distinguishing true infection from contamination when MRSE is isolated from blood cultures
Local measures (eg, mupirocin for impetigo, incision and drainage of abscess) are sufficient for some skin and soft tissue infections, but antibiotic therapy is appropriate for larger abscesses, cellulitis, and presence of risk factors; appropriate agents include trimethoprim-sulfamethoxazole, doxycycline, clindamycin, and linezolid
More severe MRSA infections and MRSE infections require parenteral therapy, usually with vancomycin, daptomycin, or linezolid
Removal of prosthetic material is recommended in most cases due to formation of biofilm; criteria exist for salvage of intravascular and peritoneal dialysis catheters
MRSA bloodstream infections and pneumonia are associated with high morbidity and mortality; skin and soft tissue infections are associated with high rates of recurrence
Routine screening of the general population is not recommended; screening of hospital patients is controversial but is mandated in some places (eg, United Kingdom)
Prevention of infection is best achieved through good hygiene (especially handwashing) and barrier precautions; decolonization with mupirocin and/or chlorhexidine may be effective in preventing hospital-acquired infection (especially in clean orthopedic and cardiothoracic procedures) and in breaking the cycle of recurrences in individual patients or households

MRSA and MRSE infections are caused by methicillin-resistant strains of staphylococci, which continue to increase in prevalence in both health care and community contexts
- Resistance to methicillin is associated with resistance to almost all β-lactam antibiotics (except ceftaroline), thus limiting treatment choices
Staphylococcus aureus (including methicillin-resistant strains) is characterized by virulence and invasiveness; major categories of infection are skin and soft tissue, bacteremia, endocarditis, pneumonia, septic arthritis, osteomyelitis, and septic bursitis
- Community-acquired MRSA is most commonly associated with necrotizing soft tissue infections and severe pneumonia
Other staphylococci, such as Staphylococcus epidermidis, are generally less virulent and invasive, and infection is usually associated with presence of a foreign body (eg, vascular catheter, prosthetic cardiac valve or device, prosthetic joint, cerebrovascular shunt, peritoneal dialysis catheter)
- Those species of clinical relevance are often resistant to methicillin

Classification

By microbiology
- Staphylococci, whether methicillin-resistant or not, are gram-positive cocci that are easily grown on conventional media and classified as coagulase-positive or coagulase-negative
  - Coagulase-positive
    - Staphylococcus aureus is the only coagulase-positive staphylococcus of widespread clinical importance
      - Methicillin-resistant strains are further characterized as health care–associated or community-acquired
        Originally, MRSA was almost exclusively associated with health care settings, and was characterized by resistance to multiple antibiotics (β-lactams and others)
        Community-acquired MRSA emerged decades after health care–associated MRSA, and distinct genetic and antibiotic susceptibility patterns (as well as epidemiology) distinguished the two
        More recently, genetically identified community-acquired strains have been found increasingly in health care settings, and these strains have become more broadly resistant to antibiotics
  - Coagulase-negative
    - Staphylococcus epidermidis is the most common; the others are often considered in the same clinical context and referred to collectively, if inaccurately, as MRSE (methicillin-resistant Staphylococcus epidermidis)
      - Staphylococcus lugdunensis is notable for behaving more like Staphylococcus aureus than the others of this group; it is also less frequently methicillin-resistant
      - Staphylococcus haemolyticus is often resistant to glycopeptides as well as methicillin and other β-lactam antibiotics
By clinical syndrome
- Clinical syndromes associated with methicillin-resistant staphylococci:
  - Skin and soft tissue infections
    - Community-acquired MRSA skin and soft tissue infections may present as impetigo, purulent cellulitis, furunculosis (boils), folliculitis, or abscess
    - MRSA infection may complicate surgical incisions
    - MRSA is commonly implicated in diabetic foot infections
    - MRSE rarely plays a significant role in skin and soft tissue infections
  - Bacteremia
    - MRSA bacteremia may occur spontaneously or result from dissemination from a primary source
      - Subclassified as uncomplicated (ie, no endocarditis, no prosthetic device, negative results on follow-up blood cultures, no metastatic infection) or complicated (ie, does not meet criteria for uncomplicated)
    - MRSE bacteremia is almost always associated with a vascular access device
  - Infective endocarditis
    - MRSA is a common cause of endocarditis on both native and prosthetic valves
      - May be associated with injection of illicit drugs
    - MRSE is occasionally implicated in native valve endocarditis and is a common cause of prosthetic valve endocarditis
  - Pneumonia
    - Community-acquired pneumonia due to MRSA often follows influenza or influenzalike infection; disease due to community-acquired strains is characterized by severe necrotizing infection with hemoptysis
    - MRSA pneumonia may occur in the hospital setting, often in patients who are receiving or recently received mechanical ventilation
    - MRSE is not associated with pneumonia
  - Bone and joint infections
    - Joint infections caused by MRSA are unusual, but when they occur they are usually associated with bacteremia or instrumentation (eg, aspiration, injection, arthroscopy) of native or prosthetic joint
    - Osteomyelitis due to MRSA may be associated with a fixation device or prosthesis, hematogenous infection in children, or nonhealing foot ulcers in patients with diabetes and/or peripheral artery disease
    - Bone and joint infection caused by MRSE is usually associated with a prosthetic joint or fixation device
    - Vertebral osteomyelitis may result from bacteremia with either MRSA or MRSE
  - Infections associated with access devices and shunts
    - Both MRSA and MRSE are associated with intravascular access devices, implantable cardiac devices, peritoneal dialysis catheters, and cerebrospinal fluid shunts
  - Epidural abscess
    - May be spinal or intracranial
    - May arise from hematogenous seeding, extension from a contiguous focus, or direct inoculation

History

History varies by infecting organism and site of infection; MRSA tends to cause more clinically overt manifestations, whereas infections caused by coagulase-negative staphylococci (except Staphylococcus lugdunensis) tend to be more subtle
General
- May have history of intravascular access (including IV injection of illicit drugs) or placement of a prosthetic device
- Infection with MRSA is usually associated with an acute onset over several days; infections due to MRSE may be more indolent
- Patients may or may not report fever; patients with severe infections such as bacteremia, endocarditis, pneumonia, or septic joint may experience chills or even rigors
Community-acquired MRSA skin and soft tissue infections
- May associate infection with a spider bite, although a bite is rarely well documented and history is usually speculative based on the appearance of the infection
Pneumonia
- Community-acquired MRSA pneumonia
  - Present with rapidly progressive pulmonary symptoms including dyspnea and hemoptysis
  - Often follows influenza or an influenzalike infection
- Hospital-acquired or ventilator-associated pneumonia due to MRSA
  - May have a history of recent IV antibiotic therapy or intubation and mechanical ventilation
  - Dyspnea and productive cough indistinguishable from those of nosocomial pneumonia caused by other pathogens
Septic arthritis
- MRSA
  - Sudden onset of severe pain and swelling at the joint
  - May be spontaneous, may follow instrumentation (eg, aspiration, injection, arthroscopy), or may be associated with a prosthetic joint
- MRSE
  - Usually occurs as a complication of prosthetic joint placement
  - Slow progression of pain and joint instability (loosening of prosthesis)
Vertebral osteomyelitis due to MRSA or MRSE
- Progressively severe, sometimes excruciating, back pain
- May be associated with radicular pain, urinary retention, constipation, and lower extremity paresthesias or weakness
Peritonitis due to infection (MRSA or MRSE) of a dialysis catheter
- Abdominal pain; patients may report cloudy dialysate
Cerebrospinal fluid shunt infections (MRSA or MRSE)
- Headache, lethargy, and change in mental status, with or without systemic symptoms
- May have erythema or tenderness over subcutaneous shunt or signs of peritonitis or pleuritis depending on location of distal shunt

Physical examination

Fever may or may not be present; it is often absent in relatively minor skin and soft tissue infections such as folliculitis
Patients with severe infections such as bacteremia, endocarditis, or pneumonia may exhibit signs of sepsis (eg, hypotension, tachycardia, toxic appearance)
Examination of the eyes may find conjunctival petechiae or retinal Roth spots in patients with endocarditis
Neck stiffness may be elicited in patients with cerebrospinal fluid shunt infection
Rales, rhonchi, and/or dullness to percussion may be elicited in patients with MRSA pneumonia; decreased breath sounds or egophony suggest pleural effusion
Cardiac examination may find a murmur in patients with endocarditis; prosthetic valve sounds may be muffled
In patients with infected peritoneal dialysis catheters, the abdomen may be diffusely tender with peritoneal signs (eg, decreased bowel sounds, rebound) and the catheter exit site may exhibit erythema, tenderness, and/or purulence
Patients with vertebral osteomyelitis have pain on truncal movement and tenderness on percussion of the affected vertebrae
- Other findings associated with impingement on cord or spinal nerves include distended bladder, sensory loss below the level of infection, weakness below the level of infection, and positive Babinski reflex
Examination of a symptomatic joint may find erythema, calor, effusion, and decreased range of motion; these findings are more likely with MRSA than with MRSE, in which findings are often very subtle
- In cases of prosthetic joint infection, a sinus tract may be present along the incision line and purulent or cloudy drainage may be observed
Numerous skin findings may be present in either MRSA or MRSE infections:
- Appearance of impetigo varies according to timeline, but lesions may be vesicular or crusted, with or without erythema
- Erythema and purulence may be present at current or recent vascular access sites; infections of tunneled catheters may have erythema, tenderness, and induration or fluctuancy over the tunnel
- Infections of implanted cardiac devices may be associated with calor, erythema, and fluctuancy over the pocket
- Surgical or other wounds may have erythema and purulence
- Cellulitis due to community-acquired MRSA is often characterized by a dark area of necrosis surrounded by erythema; fluctuancy may be noted, and purulent drainage may drain spontaneously or on incision
- Janeway lesions and splinter hemorrhages may be detected in patients with endocarditis

Causes and Risk Factors

Causes

Exposure to MRSA in the community or health care setting may cause infection acutely or may result in colonization, which predisposes to future infection
MRSE infection usually results from entry of skin flora at access site of a vascular or peritoneal dialysis catheter, contamination of a prosthetic device by skin flora at the time of implant, or secondary seeding of a catheter or device during MRSE bacteremia

Risk factors and/or associations

MRSA and MRSE

Patients with central venous access catheters
Patients with other devices and prostheses
- Prosthetic cardiac valves, pacemakers, or defibrillators
- Prosthetic joints
- Peritoneal dialysis catheters
- Cerebrospinal fluid shunts
- Breast implants
Patients with neutropenia
Premature neonates

Additional MRSA risk factors

Health care–associated
- Hospital admission
- Residence in a long-term care facility
- Dialysis
- Chronic wound care
- IV antibiotic exposure
Community-acquired
- Athletes
- Military personnel
- Incarcerated people
- People who inject illicit drugs
- Household contacts of MRSA-colonized or MRSA-infected people

Age

Children are at higher risk for community-acquired MRSA infections
Premature neonates are at high risk for MRSA and MRSE infections because of immature immune systems, in addition to frequency of invasive procedures

Ethnicity/race

In the United States, African Americans are at increased risk for community-acquired MRSA infection

Other risk factors/associations

Colonization of anterior nares is present in 20% to 30% of population
- Increased rates of colonization are found in people who use IV drugs, those who undergo dialysis, and those with diabetes, cirrhosis, HIV, or atopic dermatitis

How is Methicillin Resistant Staphylococcus Infections diagnosed?

History and physical findings may provide clues to the presence and site of infection; site of infection and presence of risk factors may raise suspicion for a specific pathogen and antibiotic susceptibility pattern
- Consider community-acquired MRSA as a pathogen in patients with skin and soft tissue infections who engage in sports or other activities that involve skin to skin contact (eg, wrestling) or turf abrasions (eg, football)
- Consider MRSA as a potential pathogen in patients with a history of exposure to the health care system (eg, recent hospital admission, kidney disease requiring dialysis, chronic wound care, prior treatment with IV antibiotics)
Definitive diagnosis of MRSA or MRSE infection is established by laboratory testing
- Obtain relevant specimens for Gram stain and culture
  - Spontaneous drainage or purulent material obtained through surgical incision or aspiration of an abscess; do not culture intact skin
  - Respiratory secretions for patients with pneumonia
    - Pleural fluid if empyema is suspected
  - Synovial fluid if prosthetic or native joint infection is suspected
  - Dialysis effluent, when peritonitis is suspected
  - Cerebrospinal fluid if shunt infection is suspected
- Obtain blood culture specimens in cases of suspected bacteremia (including those due to vascular access or cardiac device), endocarditis, severe skin and soft tissue infection, septic joint, sepsis, or severe pneumonia, as well as in all inpatients with pneumonia empirically treated for MRSA
  - When possible, obtain before starting empiric antibiotic therapy
  - For suspected infection of an intravascular catheter, obtain simultaneous blood cultures from the catheter and from a peripheral site; if it is not possible to obtain a peripheral culture, obtain blood cultures from different catheter lumens
    - If the technology is available, lumen and peripheral specimens should be cultured quantitatively
    - If the catheter is removed, send tip for semiquantitative or quantitative culture
  - If endocarditis is a possibility, collect 3 blood culture specimens over the course of at least 1 hour
  - Request minimum inhibitory concentrations for vancomycin and daptomycin for MRSA blood culture isolates
- Reporting of MRSA is required in some jurisdictions; consult public health authorities
Obtain cell counts with differential and chemistry panel on any body fluid collected for culture (pleural, peritoneal, synovial, cerebrospinal fluid)
Other laboratory tests may be appropriate for evaluating and managing severe infections: CBC, serum chemistry panel including renal function, erythrocyte sedimentation rate, C-reactive protein level (endocarditis, osteomyelitis , prosthetic joint infection), and lactate level (sepsis )
Imaging is indicated in the evaluation of pneumonia (plain radiographs), osteomyelitis (plain radiographs, MRI), prosthetic joint infection (labeled leukocyte scintigraphy), endocarditis (echocardiogram), and cerebrospinal fluid shunt infection (MRI, CT)
Biopsy may be indicated for evaluation of osteomyelitis

Laboratory

Gram stain and culture of specimen from infected site
- By definition, culture of the infected site yields MRSA or MRSE
- As both may colonize skin, positive results require interpretation of clinical significance
  - In general, Staphylococcus aureus (including MRSA) is more likely to be a pathogen than a contaminant or inactive colonizer, especially when signs or symptoms of infection are present; the significance of coagulase-negative staphylococci is more difficult to determine
  - For either MRSA or MRSE, the following parameters (alone or in combination) suggest that the isolate is a true pathogen:
    - Growth in pure culture (single species isolated), and/or isolated from multiple specimens
    - Gram stain evidence of gram-positive cocci in clusters and numerous polymorphonuclear cells
    - Cell counts and chemistry panel results of normally sterile body fluids that are consistent with infection
Blood cultures
- Staphylococcus aureus (including MRSA) is usually (and should be) considered to be a pathogen, not a contaminant, even if isolated from only 1 culture bottle
- For coagulase-negative staphylococci (including MRSE), the following parameters (alone or in combination) suggest that the isolate is a true pathogen:
  - At least 2 bottles from different sets of blood cultures are positive
  - Blood culture becomes positive within 16 hours
  - Species is Staphylococcus epidermidis
  - Central venous catheter or prosthetic heart valve is present
  - Neutropenia is present
  - Severity of illness is high (as measured by Pitt or Charlson scores)
- Intravascular catheter infection is suggested by any of the following:
  - Blood culture from lumen becomes positive at least 2 hours before peripherally drawn culture
  - Quantitative blood cultures from lumen show 3-fold higher bacterial count than peripheral blood culture
  - Growth of 15 or more colonies from semiquantitative culture of catheter tip
  - Growth of 100 or more colonies from quantitative culture of catheter tip
  - Same organism is cultured from both percutaneous blood culture and catheter tip culture
- Blood culture isolate with vancomycin minimum inhibitory concentration more than 2 mcg/mL indicates that an alternative to vancomycin should be used

Imaging

Radiography of area of interest
- Plain radiographs are indicated, as for the initial evaluation in all patients with suspected osteomyelitis, septic arthritis, or severe soft tissue infection
  - Often unhelpful in soft tissue infection, but may show previously unknown foreign body or may suggest an alternative diagnosis (eg, necrotizing fasciitis)
  - Changes suggesting osteomyelitis include periosteal thickening, lytic lesions, endosteal scalloping, and osteopenia
    - Bone destruction caused by osteomyelitis may not be evident until 10 to 21 days after onset of infection
- Chest radiograph
  - Indicated in all patients with suspected pneumonia or septic pulmonary emboli
  - Pneumonia due to community-acquired strains of MRSA is characterized by necrotizing cavitary infiltrates and is frequently associated with empyema
MRI or CT of area of interest
- MRI is the imaging modality of choice for suspected osteomyelitis, epidural abscess, septic arthritis, or soft tissue infection
  - Can detect osteomyelitis within 3 to 5 days of disease onset, which is particularly relevant in cases of vertebral osteomyelitis, which may appear shortly after (or during) a bacteremic event and can have catastrophic complications
  - Changes that suggest osteomyelitis include destruction of medulla as well as periosteal reaction, cortical destruction, articular damage, and soft tissue involvement
  - CT is useful if MRI is not feasible
- MRI or CT is indicated in patients with suspected cerebrospinal fluid shunt infection
  - May indicate complications such as brain abscess, subdural empyema, hydrocephalus, vasculitis, or thrombosis
Labeled leukocyte scintigraphy
- Indicated in the evaluation of prosthetic joint infection if there is diagnostic doubt; increased activity in area of joint suggests infection
- Also indicated as an alternative method to evaluate the possibility of osteomyelitis if MRI or CT is nondiagnostic or cannot be done (eg, when extensive hardware is present)
- Utility may vary depending on radiologist’s experience with interpretation
Echocardiogram
- Recommended in all adults with bacteremia due to Staphylococcus aureus (including MRSA)
- Recommended in patients with coagulase-negative bacteremia (including MRSE) if there is suspicion of endocarditis (eg, sustained bacteremia, prosthetic valve or other implanted cardiovascular device, embolic phenomena)
- Transesophageal approach is preferred
- Evidence of endocarditis includes vegetations on valves or other intracardiac structures (whether native or prosthetic), leaflet destruction, paravalvular abscess, and dehiscence of prosthetic valve

Procedures

Thoracentesis

General explanation

Insertion of a small-gauge needle between the ribs, through the thorax, and into the pleural space to access pleural fluid
Procedure can be performed with or without ultrasonographic guidance

Indication

Pleural effusion with underlying pneumonia

Contraindications

No absolute contraindications
Relative contraindications
- Uncorrected coagulopathy
- Mechanically ventilated patient
- Bilateral thoracentesis should be done only after ensuring absence of pneumothorax in the first side

Complications

Bleeding (eg, hematoma, hemothorax, hemoperitoneum)
Pneumothorax
Infection (empyema or soft tissue infection)
Spleen or liver puncture
Vasovagal events
Retained intrapleural catheter fragments

Interpretation of results

Empyema is suggested by:
- Protein level more than 3 g/dL
- Ratio of pleural fluid protein to serum protein more than 0.5
- Lactate dehydrogenase level more than 200 units/L
- Ratio of pleural fluid lactate dehydrogenase to serum lactate dehydrogenase more than 0.6
- Glucose level lower than 60 mg/mL
- Low pH (less than 7)
- Leukocytosis (WBC count may exceed 50,000 cells/mm³ with neutrophils predominating)
- Culture positive for MRSA; may not be seen on Gram stain

Arthrocentesis

General explanation

Insertion of a hollow-bore needle into the joint space to obtain synovial fluid

Indication

Suspected septic arthritis or prosthetic joint infection

Contraindications

Overlying skin infections or lesions
Coagulopathy or use of anticoagulant medications; safety not established
Concurrent bacteremia; relative contraindication for native joint, absolute for prosthetic joint
Prosthetic joints should be tapped only by an experienced expert

Complications

Introduction of infection

Interpretation of results

Predominance of polymorphonuclear WBCs is typical of infection
- Native joint
  - Cell count usually exceeds 50,000 cells/mm³
- Prosthetic joint:
  - Cell counts as low as 1700 cells/mm³ have been associated with infection
Culture positive for MRSA or MRSE; may not be seen on Gram stain

Lumbar puncture (or alternative means of obtaining cerebrospinal fluid from a shunt or indwelling device)

General explanation

Insertion of a hollow-bore needle between the vertebral bodies into the subarachnoid space to obtain a specimen of cerebrospinal fluid or to measure opening pressure

Indication

To collect and examine cerebrospinal fluid and measure intracranial pressure

Contraindications

Uncontrolled coagulopathy
Skin infection at site of needle insertion
Epidural abscess
Patient at risk of brain herniation
Best predictors of precipitating herniation include:
- Deteriorating level of consciousness (particularly to a Glasgow Coma Scale score of 11 or less)
- Brainstem signs (eg, pupillary changes, abnormal posturing, irregular respirations)
- Very recent seizure

Complications

Contamination and infection of the shunt
Epidural hematoma

Interpretation of results

Bacterial infection is suggested by:
- WBC count 100 to 50,000 cells/mm³, predominantly neutrophils
- Glucose level less than 40% of concurrent serum level
- Protein level elevated (more than 1 g/L)
- Culture positive for MRSA or MRSE; may not be seen on Gram stain
In patients with recent surgery, cell count and chemistry abnormalities may result from procedure

Analysis of peritoneal dialysate

General explanation

Peritoneal dialysate is collected from a postexchange bag after a dwell time of at least 2 hours

Indication

Abdominal pain, reports of cloudy drainage in a peritoneal dialysis patient

Interpretation of results

Cell count of more than 100 cells/mm³ or differential count of 50% or more polymorphonuclear cells suggests peritonitis; specific pathogen may be identified on culture

Bone biopsy

General explanation

Sampling of bone for cytopathologic or histopathologic examination and microbiologic culture
Biopsy specimens may be obtained surgically or by needle aspiration with radiologic guidance

Indication

Suspected osteomyelitis: for definitive diagnosis and identification of causative pathogen

Interpretation of results

Gold standard for diagnosis of osteomyelitis is positive culture result from bone biopsy accompanied by histopathologic signs of necrosis
Culture positive for MRSA or MRSE

Debridement of surgical wound

General explanation

Surgical wound is reopened and examined; cultures are obtained and unhealthy tissue is debrided

Indication

Wound erythema, drainage, or dehiscence
Rim-enhancing collection on imaging of the surgical site with signs or symptoms of infection (eg, fever, increased pain)

Interpretation of results

Purulent fluid suggests infection
Culture positive for MRSA or MRSE

Bronchoscopy

General explanation

Evaluation of respiratory tract (ie, upper airway, trachea, proximal airways, segmental airways to third generation of branching) using either rigid or flexible bronchoscope
Specimens of lung secretions can be obtained using a protected brush catheter or by bronchoalveolar lavage
Procedure is performed under anesthesia by otolaryngologist, pulmonary subspecialist, or thoracic surgeon

Indication

To obtain specimens of deep respiratory secretions primarily in patients with pneumonia who cannot expectorate sputum

Contraindications

Absolute
- Hemodynamic instability
- Uncontrolled coagulopathy
Relative
- Severe pulmonary hypertension
- Superior vena cava syndrome
- Complications

Complications

Hypoxia
Hypotension related to sedation
Bronchospasm
Epistaxis
Vomiting
Pneumothorax
Cardiac arrhythmias
Laryngeal edema, injury, or spasm

Interpretation of results

Specimens are submitted for Gram stain and culture for determination of causative organism
In patients with ventilator-associated pneumonia, quantitative and semiquantitative culture reports can help distinguish pneumonia from colonization

Differential Diagnosis

Most common

Skin and soft tissue infections
Bacteremia
Infectious endocarditis
Pneumonia – Bronchitis (Related: Acute bronchitis)Infection of the bronchi, without involvement of the lung parenchyma

Presents with fever, malaise, productive cough, hoarseness, and chest pain

Differentiated by chest radiography and physical examinationNo radiographic evidence of pulmonary pathology

Signs of consolidation that are indicative of pneumonia (eg, rales, egophony, fremitus) are absent

Influenza Viral respiratory infection

Like MRSA pneumonia, it is characterized by sudden onset of high fever with chills, myalgia, or malaise

Unlike with MRSA pneumonia, the cough is nonproductive, and the illness is accompanied by sneezing, sore throat, and nasal discharge

Differentiated by history and laboratory testing (eg, rapid antigen testing via polymerase chain reaction)Note that MRSA pneumonia often occurs as a complication of influenza, so there may be clinical overlap

Pulmonary embolismSudden occlusion of a pulmonary artery, most often due to a dislodged thrombus

Like MRSA pneumonia, may be characterized by dyspnea, tachypnea, and bloody sputum

Unlike with pneumonia, chest radiograph does not usually show an infiltrate

Diagnosed by multidetector-row CT angiography or CT pulmonary angiography; D-dimer levels are usually elevated

Tuberculosis Pulmonary infection due to Mycobacterium tuberculosis

Reactivated disease, like community-acquired MRSA pneumonia, may present with fever, bloody sputum, and cavitary infiltrates

Presentation of tuberculosis is more indolent and subacute than presentation of MRSA pneumonia, and the pattern of cavitation is usually apical

Definitive differentiation is by identification of Mycobacterium tuberculosis on sputum smears or culture

Treatment Goals

Eradicate infection
Prevent complications

Admission criteria

Patients with severe infection or suspicion thereof (eg, bacteremia, infectious endocarditis, pneumonia, septic joint, infected device) usually require admission

Criteria for ICU admission

Septic shock
Pneumonia with significant respiratory impairment
Endocarditis with embolization, pulmonary edema, ring abscess, conduction delays, or evidence of prosthetic valve dehiscence

Recommendations for specialist referral

Consult infectious disease specialist for interpretation of culture results, selection and management of antibiotics, and monitoring of response to therapy
For patients with severe soft tissue infection requiring drainage or debridement, consult a general surgeon
For patients with endocarditis, consult the following:
- Cardiologist to interpret echocardiogram and manage complications
- Cardiothoracic surgeon to determine whether and when valve replacement may be necessary
For patients with pneumonia, consult a pulmonologist to evaluate and manage respiratory compromise
For patients with bone or joint infection, consult an orthopedic surgeon for biopsy and debridement of osteomyelitis, arthroscopic joint lavage, and removal and replacement of infected prosthetic joint
For patients with other infected devices, consult the appropriate interventionist:
- Cardiac electrophysiologist or cardiac surgeon to remove infected pacemaker or defibrillator
- Neurosurgeon to remove infected cerebrospinal fluid shunt
- General or vascular surgeon to remove IV access catheters
- Patients with infected peritoneal dialysis catheters are usually managed by a nephrologist, in collaboration with a surgeon if catheter removal is required
For patients with epidural abscess, consult neurosurgeon for urgent surgical drainage

Treatment Options

Skin and soft tissue infections

Abscesses:
- For patients with small (less than 5 cm), relatively superficial cutaneous abscesses, incision and drainage suffice
- Antibiotic therapy with activity against MRSA is recommended in addition to incision and drainage in the following situations:
  - Multiple or large abscesses
  - Rapid progression
  - Associated cellulitis
  - Systemic signs of sepsis
    - Temperature more than 38°C or less than 36°C
    - Respiratory rate more than 24 breaths per minute (in adults)
    - Heart rate more than 90 beats per minute (in adults)
    - WBC count more than 12,000 or less than 4000 cells/mm³
  - Impaired host defenses or significant comorbidity
  - Difficult site to drain adequately (eg, hand, face)
Empiric antibiotic therapy with activity against MRSA is recommended for purulent cellulitis without a defined abscess
For nonpurulent cellulitis, empiric antibiotic therapy should include coverage of MRSA in the following circumstances:
- Known colonization with MRSA
- Clinical presentation suggestive of MRSA infection
- Cellulitis associated with penetrating trauma
- Patient injects illicit drugs
- Infection has not responded to β-lactam therapy or other conventional regimen for methicillin-susceptible Staphylococcus aureus and/or β-hemolytic streptococci
Impetigo that is known or suspected to be caused by MRSA may be treated topically with mupirocin or, if severe, with oral agents
Oral agents recommended for treatment of skin and soft tissue infections due to MRSA include trimethoprim-sulfamethoxazole, doxycycline, minocycline, clindamycin, and linezolid
- If empiric coverage of β-hemolytic streptococci is also indicated, choices include clindamycin or linezolid alone, or a combination of either trimethoprim-sulfamethoxazole or doxycycline plus a β-lactam
- Increasing prevalence of resistance to clindamycin is a concern; susceptibility should be verified by culture
For patients with severe skin or soft tissue infection requiring hospital admission, guidelines recommend vancomycin, daptomycin, telavancin, or linezolid; ceftaroline is also approved for treatment of severe skin and soft tissue infections due to MRSA
When antibiotics are indicated, the usual course is 5 to 10 days for mild to moderate infection, or 7 to 14 days for more severe disease

Bacteremia

MRSA
- Uncomplicated MRSA bacteremia is defined by:
  - Exclusion of endocarditis
    - Echocardiography, preferably transesophageal, is recommended for all patients with MRSA bacteremia
  - Absence of implanted prosthesis or device
  - Defervescence within 72 hours of starting appropriate antibiotics
  - Negative result on follow-up blood cultures obtained 2 to 4 days after initial set
  - Absence of metastatic infection
- Complicated bacteremia is any that does not meet the criteria for uncomplicated bacteremia
- Recommended treatment is either vancomycin or daptomycin for a minimum of 2 weeks for uncomplicated bacteremia and 4 to 6 weeks for complicated bacteremia
- Vancomycin should not be used if the minimum inhibitory concentration is more than 2 mcg/mL
- Removal or drainage of any implicated source is an integral component of treatment
MRSE
- Removal of IV access catheter is reasonable if it is no longer needed or easily replaced
- Removal is not necessary in uncomplicated cases, defined as follows:
  - Resolution of fever within 72 hours
  - No evidence of endocarditis or suppurative thrombophlebitis
  - No other intravascular hardware
  - Follow-up blood cultures confirm clearance
- Recommended treatment is vancomycin for 5 to 7 days if catheter is removed, or 10 to 14 days if catheter is retained
  - If the catheter is retained, antibiotics should be administered both systemically and in an antibiotic lock (preferably); if the latter is not feasible, the systemic antibiotics should be infused through the colonized catheter

Endocarditis

MRSA or MRSE
- For endocarditis involving native valves, a 6-week course of either vancomycin or daptomycin is recommended
- For endocarditis involving prosthetic valves, vancomycin plus rifampin is recommended for 6 weeks or more, along with gentamicin for the first 2 weeks
- Valve replacement surgery should be considered in patients with prosthetic valve infection and may be required in patients with certain complications from native valve infection
- Source of infection should be identified and eliminated

Pneumonia

Recommended treatment is vancomycin or linezolid for 7 to 21 days
Some authorities favor linezolid or clindamycin over vancomycin
Ceftaroline is an option if linezolid or vancomycin cannot be used
Daptomycin is ineffective in treating pulmonary infections and should not be used

Bone and joint infections

Septic native joint
- Recommended options are daily aspiration until dry or surgical debridement and irrigation; the latter may be open or arthroscopic
- For MRSA infection, a 3- to 4-week course of vancomycin or daptomycin is recommended; it is unclear whether oral agents are equally effective, although linezolid is a reasonable option
Prosthetic joint infection due to MRSA or MRSE
- In patients who have no systemic signs of infection and who are not bacteremic, antibiotic treatment is often withheld until surgery so that specimens for culture may be obtained
- Surgery is recommended in most patients; extent depends on time elapsed since prosthesis-implanting surgery and on condition of patient
  - For patients with a stable joint whose infection occurs within 30 days of surgery or who have had symptoms of infection for less than 3 weeks, debridement without removal of the implant may be considered
  - Otherwise, removal and replacement of the joint is recommended in mobile patients who can tolerate surgery; this may be done in 1 or 2 stages
- Regardless of surgical approach chosen, treatment is begun with vancomycin with or without rifampin for 2 to 6 weeks followed by a well-absorbed oral agent (eg, doxycycline, minocycline, trimethoprim-sulfamethoxazole) with or without rifampin
  - Total duration of therapy depends on surgical approach and response to therapy
    - Oral antibiotic therapy is recommended for 3 months for retained hip implants and 6 months for retained knee hardware
    - May be continued indefinitely in cases in which the prosthesis is retained
  - If patients are unable to tolerate long-term vancomycin therapy owing to renal impairment, alternative agents include daptomycin, telavancin, linezolid, and ceftaroline
Vertebral osteomyelitis, diskitis, or epidural abscess
- Require urgent neurosurgical evaluation to exclude epidural abscess
- Epidural abscess requires immediate drainage and antibiotic therapy

Other infections involving implanted devices

Implantable cardiac devices
- Removal of device is recommended for any infection other than superficial infection at pocket site without device involvement
- Vancomycin is recommended in conjunction with device removal; duration depends on extent of infection
  - 14 days for infection limited to pocket
  - At least 2 weeks for patients with associated bacteremia; patients with sustained bacteremia even despite removal or those with metastatic infection should receive at least 4 to 6 weeks of vancomycin even if transesophageal echocardiographic findings do not suggest endocarditis
- Reassess need for device replacement in all patients; replace in an alternate location after blood culture results have been negative for at least 72 hours
- In patients whose device cannot be removed, long-term suppressive treatment with an oral agent to which the isolated pathogen is sensitive may be recommended
Cerebrospinal fluid shunts
- Complete removal of device is recommended
- Vancomycin is the drug of choice; consider addition of rifampin if the organism is susceptible, particularly if a shunt or hardware is involved
- Daptomycin and linezolid are alternatives if vancomycin cannot be used or is ineffective
- For patients with MRSE infection, recommended duration of treatment is 10 days after last positive cerebrospinal fluid culture result if patient is minimally symptomatic and cerebrospinal fluid has normal glucose level and minimal pleocytosis; otherwise, 14 days is recommended
- For patients with MRSA infection, 14 to 21 days of antibiotic treatment is recommended after last positive cerebrospinal fluid culture result
- For patients with poor clinical response to therapy, intrathecal vancomycin may be added
Infections related to peritoneal dialysis
- MRSA
  - When either exit site infection or peritonitis occurs, catheter tunnel is often involved even if involvement is not clinically evident, necessitating removal of catheter in addition to IV vancomycin
  - Recommendations suggest that Staphylococcus aureus peritonitis be treated for 3 weeks
- MRSE
  - Recommendations suggest treatment with intraperitoneal vancomycin for 2 weeks
  - Infections of either the exit site or the peritoneal cavity may respond to antibiotic therapy alone, without removing catheter
  - Relapsing coagulase-negative staphylococcus peritonitis suggests colonization of the catheter with biofilm; consider catheter removal

Drug therapy

Glycopeptide
- Vancomycin
  - Adjust dose and frequency to achieve goal trough concentration of 15 to 20 mcg/mL
  - Skin and soft tissue infections
    - Vancomycin Hydrochloride Solution for injection; Neonates: 15 mg/kg/dose IV, then 10 mg/kg/dose IV every 12 hours for first week of life then increase to every 8 hours per FDA-approved dosage. AAP recommends dosing based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested. Treat for 7 to 14 days for complicated skin and skin structure infections due to MRSA.
    - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: 40 to 60 mg/kg/day IV divided every 6 hours; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. Treat for 7 to 14 days for complicated skin and skin structure infections due to MRSA.
    - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose for seriously-ill patients, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours per guidelines. Adjust dose based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. Treat for 7 to 14 days for complicated skin and skin structure infections due to MRSA.
  - Bacteremia
    - Vancomycin Hydrochloride Solution for injection; Neonates: 15 mg/kg/dose IV, then 10 mg/kg/dose IV every 12 hours for first week of life then increase to every 8 hours per FDA-approved dosage. AAP recommends dosing based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested. For MRSA, treat at least 2 weeks for uncomplicated bacteremia and 4 to 6 weeks for complicated bacteremia.
    - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: 40 to 60 mg/kg/day IV divided every 6 hours; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. For MRSA, treat at least 2 weeks for uncomplicated bacteremia and 4 to 6 weeks for complicated bacteremia.
    - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours per guidelines. Adjust dose based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. For MRSA, treat at least 2 weeks for uncomplicated bacteremia and 4 to 6 weeks for complicated bacteremia.
  - Endocarditis
    - Vancomycin Hydrochloride Solution for injection; Neonates: FDA-approved dosage is 15 mg/kg/dose IV initially, then 10 mg/kg/dose IV every 12 hours for the first week of life, then increase to every 8 hours. AAP recommends the following general dosing schedule based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested.
    - Vancomycin Hydrochloride Solution for injection; Infants: 40 to 60 mg/kg/day IV divided every 6 hours in combination with appropriate antimicrobial therapy depending on causative microorganism; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations.
    - Vancomycin Hydrochloride Solution for injection; Children and Adolescents: 40 to 60 mg/kg/day IV divided every 6 to 12 hours in combination with appropriate antimicrobial therapy depending on causative microorganism; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. Treat for at least 4 to 6 weeks with duration of therapy dependent on valve type and causative microorganism.
    - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose for seriously-ill patients, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours in combination with appropriate antimicrobial agent depending on causative microorganism per guidelines. Adjust dosage based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. Treat for at least 4 to 6 weeks with duration of therapy dependent on valve type and causative microorganism.
    - When other drugs are given concomitantly with vancomycin for prosthetic valve infection, the recommended duration of gentamicin is 2 weeks, whereas rifampin is continued for the full course.
  - Pneumonia
    - Vancomycin Hydrochloride Solution for injection; Infants and Children 3 months to 12 years: 40 to 60 mg/kg/day IV divided every 6 to 8 hours for at least 10 days. Adjust dose based on serum concentrations.
    - Vancomycin Hydrochloride Solution for injection; Adolescents: 40 to 60 mg/kg/day IV divided every 6 to 8 hours for at least 10 days. Adjust dose based on serum concentrations.
    - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg IV loading dose for seriously ill patients, followed by 15 to 20 mg/kg/dose IV every 8 to 12 hours for at least 7 days. Adjust dose based on serum concentrations.
  - Bone and joint infections
    - Septic arthritis in native joint
      - Vancomycin Hydrochloride Solution for injection; Neonates: 15 mg/kg/dose IV, then 10 mg/kg/dose IV every 12 hours for first week of life then increase to every 8 hours per FDA-approved dosage. AAP recommends dosing based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested. Treat for at least 3 to 4 weeks for MRSA.
      - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: 40 to 60 mg/kg/day IV divided every 6 hours; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. Treat for at least 3 to 4 weeks for MRSA.
      - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose for seriously-ill patients, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours per guidelines. Adjust dose based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. Treat for at least 3 to 4 weeks for MRSA.
    - Osteomyelitis
      - Vancomycin Hydrochloride Solution for injection; Neonates: 15 mg/kg/dose IV, then 10 mg/kg/dose IV every 12 hours for first week of life then increase to every 8 hours per FDA-approved dosage. AAP recommends dosing based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested. Treat for at least 4 to 6 weeks for MRSA.
      - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: 40 to 60 mg/kg/day IV divided every 6 hours; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. Treat for at least 4 to 6 weeks for MRSA.
      - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose for seriously-ill patients, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours per guidelines. Adjust dose based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. Use with or without PO rifampin for at least 8 weeks; an additional 1 to 3 months (or longer) of oral combination therapy may be necessary.
    - Orthopedic device–related infection
      - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose for seriously-ill patients, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours per guidelines. Adjust dose based on serum concentrations. FDA-approved dosage is 500 mg IV every 6 hours or 1 g IV every 12 hours. Use with oral rifampin, then additional oral combination therapy for 3 months for hip infections or for 6 months for knee infections.
  - Peritonitis
    - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: Loading dose of 1,000 mg/L in IP dialysate, followed by maintenance dose of 25 mg/L of peritoneal dialysate with each exchange. Alternatively, intermittent dosage of 30 mg/kg/dose in first peritoneal dialysate exchange, then 15 mg/kg/dose every 3 to 5 days.
    - Vancomycin Hydrochloride Solution for injection; Adults: Loading dose of 1,000 mg/L in IP dialysate, followed by maintenance dose of 25 mg/L of peritoneal dialysate with each exchange. Alternatively, intermittent dosage of 15 to 30 mg/kg/dose in first peritoneal dialysate exchange, then every 5 to 7 days.
  - Cerebrospinal fluid shunt infections
    - Vancomycin Hydrochloride Solution for injection; Neonates: IDSA recommends 20 to 30 mg/kg/day IV divided every 8 to 12 hours for neonates 0 to 7 days weighing 2 kg or more or 30 to 45 mg/kg/day IV divided every 6 to 8 hours for neonates older than 7 days weighing 2 kg or more. AAP recommends dosing based on serum creatinine (SCr) concentration, which will take approximately 5 days from birth to reasonably reflect neonatal renal function: SCr less than 0.7 mg/dL: 15 mg/kg/dose IV every 12 hours; SCr 0.7 to 0.9 mg/dL: 20 mg/kg/dose IV every 24 hours; SCr 1 to 1.2 mg/dL: 15 mg/kg/dose IV every 24 hours; SCr 1.3 to 1.6 mg/dL: 10 mg/kg/dose IV every 24 hours; SCr more than 1.6 mg/dL: 15 mg/kg/dose IV every 48 hours. Dosing interval may need to be extended in neonatal patients on ECMO; doses of 20 mg/kg/dose IV every 18 to 24 hours have been suggested. Treat for 2 weeks for meningitis or for 4 to 6 weeks for brain abscess, subdural empyema, spinal epidural abscess, and septic thrombosis of cavernous or dural venous sinus.
    - Vancomycin Hydrochloride Solution for injection; Infants, Children, and Adolescents: 15 mg/kg/dose IV every 6 hours; a loading dose of 20 to 25 mg/kg IV may be considered for seriously ill patients. Adjust dosage based on serum concentrations. Treat for 10 to 14 days for meningitis depending on causative microorganism and clinical response; treat for 4 to 6 weeks for other MRSA-associated CNS infections (i.e., brain abscess, subdural empyema, spinal epidural abscess, and septic thrombosis of cavernous or dural venous sinus).
    - Vancomycin Hydrochloride Solution for injection; Adults: 25 to 30 mg/kg (actual body weight) IV loading dose, then 15 to 20 mg/kg/dose (actual body weight) IV every 8 to 12 hours. Adjust dose based on serum concentrations. Treat with or without rifampin for 10 to 14 days for meningitis depending on causative microorganism and clinical response; treat for 4 to 6 weeks for other MRSA-associated CNS infections (i.e., brain abscess, subdural empyema, spinal epidural abscess, and septic thrombosis of cavernous or dural venous sinus).
- Oxazolidinone
  - Linezolid
    - Skin and soft tissue infections
      - Linezolid Solution for injection; Premature Neonates less than 34 weeks gestation and 0 to 6 days: 10 mg/kg/dose IV every 12 hours initially; 10 mg/kg/dose every 8 hours may be given for sub-optimal clinical response. Total course = 10 to 14 days. IDSA recommends linezolid for 7 to 14 days as option for MRSA infections.
      - Linezolid Solution for injection; Premature Neonates less than 34 weeks gestation and older than 6 days: 10 mg/kg/dose IV every 8 hours for 10 to 14 days. IDSA recommends 10 mg/kg/dose IV every 8 hours for 7 to 14 days as option for MRSA.
      - Linezolid Solution for injection; Neonates 34 weeks gestation and older: 10 mg/kg/dose IV every 8 hours for 10 to 14 days. IDSA recommends 10 mg/kg/dose IV every 8 hours for 7 to 14 days as option for MRSA.
      - Linezolid Solution for injection; Infants and Children 1 to 11 years: 10 mg/kg/dose IV every 8 hours (Max: 600 mg/dose) for 10 to 14 days. IDSA recommends 10 mg/kg/dose IV every 8 hours for 7 to 14 days as option for MRSA.
      - Linezolid Solution for injection; Children and Adolescents 12 to 17 years: 600 mg IV every 12 hours for 10 to 14 days. NOTE: Not studied for decubital ulcers. IDSA recommends 600 mg IV every 12 hours for 7 to 14 days as option for MRSA.
      - Linezolid Solution for injection; Adults: 600 mg IV every 12 hours for 10 to 14 days. NOTE: Not studied for decubital ulcers. IDSA recommends 600 mg IV every 12 hours for 7 to 14 days as option for MRSA.
    - Pneumonia
      - Linezolid Solution for injection; Infants and Children 1 to 11 years: 10 mg/kg/dose (Max: 600 mg/dose) IV every 8 hours for at least 7 days.
      - Linezolid Solution for injection; Adolescents: 600 mg IV every 12 hours for at least 7 days.
      - Linezolid Solution for injection; Adults: 600 mg IV every 12 hours for at least 7 days.
    - Bone and joint infections
      - Septic arthritis in native joint
        Linezolid Solution for injection; Infants and Children 1 to 11 years: IDSA recommends 10 mg/kg/dose IV every 8 hours (Max: 600 mg/dose) for 3 to 4 weeks.
        Linezolid Solution for injection; Children and Adolescents 12 to 17 years: IDSA recommends 600 mg IV every 12 hours for 3 to 4 weeks.
        Linezolid Solution for injection; Adults: IDSA recommends 600 mg IV every 12 hours for 3 to 4 weeks.
      - Osteomyelitis
        Linezolid Solution for injection; Neonates: IDSA recommends 10 mg/kg/dose IV every 8 hours for 4 to 6 weeks.
        Linezolid Solution for injection; Infants and Children 1 to 11 years: IDSA recommends 10 mg/kg/dose IV every 8 hours (Max: 600 mg/dose) for 4 to 6 weeks.
        Linezolid Solution for injection; Children and Adolescents 12 to 17 years: IDSA recommends 600 mg IV every 12 hours for 4 to 6 weeks.
        Linezolid Solution for injection; Adults: IDSA recommends 600 mg IV every 12 hours +/- PO rifampin for at least 8 weeks; an additional 1 to 3 months (or longer) of oral combination therapy may be necessary.
      - Orthopedic device–related infection
        Linezolid Solution for injection; Adults: IDSA recommends 600 mg IV every 12 hours plus oral rifampin for 2 weeks, then additional oral combination therapy for 3 months for hip infections or for 6 months for knee infections.
    - Cerebrospinal fluid shunt infections
      - Linezolid Solution for injection; Adults: 600 mg IV every 12 hours as alternative to vancomycin recommended by IDSA; duration is 2 weeks for meningitis and 4 to 6 weeks for brain abscess, subdural empyema, spinal epidural abscess, septic thrombosis of the cavernous or dural venous sinus.
- Lipopeptide
  - Daptomycin
    - Skin and soft tissue infections
      - Daptomycin Solution for injection; Neonates†: Safety and efficacy not established; very limited data are available. Doses of 6 to 15 mg/kg/dose IV every 12 to 24 hours have been successfully used in case reports of neonates and premature neonates with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcal bacteremia. 6 mg/kg/dose IV every 12 hours most commonly reported; however, differences in peak concentrations have been observed with this dose between various studies. Doses higher than 6 mg/kg/dose may be necessary to achieve adequate drug exposure. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Off-label use in this age group
      - Daptomycin Solution for injection; Infants†: Safety and efficacy not established; limited data are available. 8 to 10 mg/kg/dose IV every 24 hours recommended based on pharmacokinetic data. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Off-label use in this age group
      - Daptomycin Solution for injection; Children younger than 2 years: 10 mg/kg/dose IV every 24 hours for up to 14 days.
      - Daptomycin Solution for injection; Children 2 to 6 years: 9 mg/kg/dose IV every 24 hours for up to 14 days.
      - Daptomycin Solution for injection; Children 7 to 11 years: 7 mg/kg/dose IV every 24 hours for up to 14 days.
      - Daptomycin Solution for injection; Children and Adolescents 12 to 17 years: 5 mg/kg/dose IV every 24 hours for up to 14 days.
      - Daptomycin Solution for injection; Adults: 4 mg/kg/dose IV every 24 hours for 7 to 14 days.
    - Bacteremia
      - Daptomycin Solution for injection; Neonates†: Safety and efficacy not established; very limited data are available. Doses of 6 to 15 mg/kg/dose IV every 12 to 24 hours have been successfully used in case reports of neonates and premature neonates with MRSA and vancomycin-resistant enterococcal bacteremia. 6 mg/kg/dose IV every 12 hours most commonly reported; however, differences in peak concentrations have been observed with this dose between various studies. Doses higher than 6 mg/kg/dose may be necessary to achieve adequate drug exposure. Treat for 2 to 6 weeks for bacteremia. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Off-label use in this age group
      - Daptomycin Solution for injection; Infants†: Safety and efficacy not established; limited data are available. Based on pharmacokinetic data, doses of 8 to 10 mg/kg/dose IV every 24 hours have been recommended in this age group; IDSA suggests 6 to 10 mg/kg/dose IV every 24 hours. Treat for 2 to 6 weeks for bacteremia. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Off-label use in this age group
      - Daptomycin Solution for injection; Children 1 to 6 years: 12 mg/kg/dose IV every 24 hours for up to 6 weeks.
      - Daptomycin Solution for injection; Children 7 to 11 years: 9 mg/kg/dose IV every 24 hours for up to 6 weeks.
      - Daptomycin Solution for injection; Children and Adolescents 12 to 17 years: 7 mg/kg/dose IV every 24 hours for up to 6 weeks.
      - Daptomycin Solution for injection; Adults: 6 mg/kg/dose IV every 24 hours is FDA-approved dosage; clinical guidelines suggest doses of 8 to 10 mg/kg/dose IV every 24 hours may be used for MRSA and 10 mg/kg/dose IV every 24 hours (plus another agent) for persistent MRSA bacteremia. Treat for at least 2 weeks for uncomplicated bacteremia and 4 to 6 weeks for complicated bacteremia.
    - Bone and joint infections
      - Septic arthritis in native joint
        Daptomycin Solution for injection; Neonates: Safety and efficacy not established; very limited data are available. Doses of 6 to 15 mg/kg/dose IV every 12 to 24 hours have been successfully used in case reports of neonates and premature neonates with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcal bacteremia. 6 mg/kg/dose IV every 12 hours most commonly reported; however, differences in peak concentrations have been observed with this dose between various studies. Doses higher than 6 mg/kg/dose may be necessary to achieve adequate drug exposure. Treat for at least 3 to 4 weeks for septic/infectious arthritis. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Daptomycin Solution for injection; Infants: Safety and efficacy not established; limited data are available. 8 to 10 mg/kg/dose IV every 24 hours recommended based on pharmacokinetic data. 6 to 10 mg/kg/dose IV every 24 hours suggested by IDSA as alternative to vancomycin for MRSA infections; treat for at least 3 to 4 weeks for septic/infectious arthritis. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Daptomycin Solution for injection; Children 1 to 6 years: Safety and efficacy not established; limited data are available. 8 to 10 mg/kg/dose IV every 24 hours recommended based on pharmacokinetic data. 6 to 10 mg/kg/dose IV every 24 hours suggested by IDSA as alternative to vancomycin for MRSA infections; treat for at least 3 to 4 weeks for septic/infectious arthritis.
        Daptomycin Solution for injection; Children and Adolescents 7 to 17 years: Safety and efficacy not established; limited data are available. 6 to 10 mg/kg/dose IV every 24 hours suggested by IDSA as alternative to vancomycin for MRSA infections; treat for at least 3 to 4 weeks for septic/infectious arthritis.
        Daptomycin Solution for injection; Adults: IDSA recommends 6 mg/kg/dose IV every 24 hours for 3 to 4 weeks.
      - Osteomyelitis
        Daptomycin Solution for injection; Neonates: Safety and efficacy not established; very limited data are available. Doses of 6 to 15 mg/kg/dose IV every 12 to 24 hours have been successfully used in case reports of neonates and premature neonates with methicillin-resistant Staphylococcus aureus and vancomycin-resistant enterococcal bacteremia. 6 mg/kg/dose IV every 12 hours most commonly reported; however, differences in peak concentrations have been observed with this dose between various studies. Doses higher than 6 mg/kg/dose may be necessary in neonates to achieve adequate drug exposure. Treat for 4 to 6 weeks for osteomyelitis. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Daptomycin Solution for injection; Infants: Safety and efficacy not established; limited data are available. 8 to 10 mg/kg/dose IV every 24 hours recommended based on pharmacokinetic data. 6 to 10 mg/kg/dose IV every 24 hours suggested by IDSA as alternative to vancomycin for MRSA infections; treat for 4 to 6 weeks for osteomyelitis. FDA-approved labeling warns against use; animal data suggests an increased risk for muscular, neuromuscular, and/or nervous system (both peripheral and central) adverse reactions in pediatric patients younger than 12 months of age. Monitoring of daptomycin serum concentrations and CPK concentrations is recommended.
        Daptomycin Solution for injection; Children 1 to 6 years: 12 mg/kg/dose IV every 24 hours based on data from a pediatric study; a general dose of 6 to 10 mg/kg/dose IV every 24 hours for 4 to 6 weeks recommended by IDSA as an alternative to vancomycin.
        Daptomycin Solution for injection; Children 7 to 11 years: 9 mg/kg/dose IV every 24 hours based on data from a pediatric study; a general dose of 6 to 10 mg/kg/dose IV every 24 hours for 4 to 6 weeks recommended by IDSA as an alternative to vancomycin.
        Daptomycin Solution for injection; Children and Adolescents 12 to 17 years: 7 mg/kg/dose IV every 24 hours based on data from a pediatric study; a general dose of 6 to 10 mg/kg/dose IV every 24 hours for 4 to 6 weeks recommended by IDSA as an alternative to vancomycin.
        Daptomycin Solution for injection; Adults: IDSA recommends 6 mg/kg/dose IV every 24 hours +/- PO rifampin for at least 8 weeks; an additional 1 to 3 months (or longer) of oral combination therapy may be necessary.
      - Orthopedic device–related infection
        Daptomycin Solution for injection; Adults: IDSA recommends 6 mg/kg/dose IV every 24 hours plus oral rifampin, then additional oral combination therapy for 3 months for hip infections or for 6 months for knee infections.
- Lipoglycopeptide
  - Telavancin
    - Skin and soft tissue infections
      - Telavancin Solution for injection; Adults: 10 mg/kg/dose IV daily x7—14 days; infuse over 60 min.
- Fifth-generation cephalosporin
  - Ceftaroline
    - Skin and soft tissue infection
      - Ceftaroline fosamil Solution for injection; Infants and Children 2 months to younger than 2 years: 8 mg/kg/dose IV every 8 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Children and Adolescents 2 to 17 years weighing 33 kg or less: 12 mg/kg/dose IV every 8 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Children and Adolescents 2 to 17 years weighing more than 33 kg: 400 mg IV every 8 hours or 600 mg IV every 12 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Adults: 600 mg IV every 12 hours for 5 to 14 days.
    - Pneumonia
      - Ceftaroline fosamil Solution for injection; Infants and Children 2 months to younger than 2 years: 8 mg/kg/dose IV every 8 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Children and Adolescents 2 years and older weighing 33 kg or less: 12 mg/kg/dose IV every 8 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Children and Adolescents 2 years and older weighing more than 33 kg: 400 mg IV every 8 hours or 600 mg IV every 12 hours for 5 to 14 days.
      - Ceftaroline fosamil Solution for injection; Adults: 600 mg IV every 12 hours for at least 5 days.
Lincosamide
- Clindamycin
  - Skin and soft tissue infections
    - Clindamycin Palmitate Hydrochloride Oral solution; Neonates 32 weeks postmenstrual age and younger: 5 mg/kg/dose PO every 8 hours.
    - Clindamycin Palmitate Hydrochloride Oral solution; Neonates 33 to 40 weeks postmenstrual age: 7 mg/kg/dose PO every 8 hours.
    - Clindamycin Palmitate Hydrochloride Oral solution; Neonates older than 40 weeks postmenstrual age: 9 mg/kg/dose PO every 8 hours.
    - Clindamycin Palmitate Hydrochloride Oral solution; Infants, Children, and Adolescents: 8 to 25 mg/kg/day PO divided every 6 to 8 hours (Max: 1,800 mg/day); for MRSA infections, 30 to 40 mg/kg/day PO divided every 6 to 8 hours (Max: 1,800 mg/day). Treat for 5 days for erysipelas, 5 to 10 days for cellulitis, and 7 to 14 days for complicated skin and soft tissue infections.
    - Clindamycin Hydrochloride Oral capsule; Adults: 150 to 450 mg PO every 6 hours. Guidelines recommend 300 to 450 mg PO every 6 to 8 hours or 600 mg PO every 8 hours. Treat for 5 days for erysipelas, 5 to 10 days for cellulitis, and 7 to 14 days for complicated skin and soft tissue infections.
  - Pneumonia
    - Clindamycin Palmitate Hydrochloride Oral solution; Infants, Children, and Adolescents: 30 to 40 mg/kg/day PO divided every 6 to 8 hours (Max: 1,800 mg/day) for 7 to 21 days.
    - Clindamycin Hydrochloride Oral capsule; Adults: 600 mg PO every 8 hours for 7 to 21 days.
  - Bone and joint infections
    - Septic arthritis and/or osteomyelitis not related to orthopedic device
      - Clindamycin Hydrochloride Oral capsule; Infants, Children, and Adolescents 13 to 16 years: 30 to 40 mg/kg/day PO (10 to 13 mg/kg/dose every 6 to 8 hours; Max: 1,800 mg/day). For MRSA, treat for 3 to 4 weeks for septic arthritis and 4 to 6 weeks for osteomyelitis.
      - Clindamycin Hydrochloride Oral capsule; Adolescents 17 years: 600 mg PO every 8 hours. For MRSA, treat for 3 to 4 weeks for septic arthritis and 4 to 6 weeks for osteomyelitis.
      - Clindamycin Hydrochloride Oral capsule; Adults: 600 mg PO every 8 hours. For MRSA, treat for 3 to 4 weeks for septic arthritis and for at least 8 weeks for osteomyelitis. For osteomyelitis, may add rifampin; an additional 1 to 3 months (or longer) of oral combination therapy may be necessary.
    - Orthopedic device–related infection
      - Clindamycin Hydrochloride Oral capsule; Adults: 600 mg PO every 8 hours plus rifampin starting after IV therapy and continuing for 3 months for hip infections or 6 months for knee infections.
Tetracyclines
- Doxycycline
  - Skin and soft tissue infections
    - Doxycycline Hyclate Oral capsule; Children 8 years and older and Adolescents weighing less than 45 kg: 2 mg/kg/dose PO every 12 hours for 5 to 10 days for CA-MRSA plus a beta-lactam if beta-hemolytic streptococci coverage is necessary.
    - Doxycycline Hyclate Oral capsule; Adults, Adolescents, and Children 8 years and older and weighing 45 kg or more: 100 mg PO every 12 hours for 5 to 10 days for CA-MRSA plus a beta-lactam if beta-hemolytic streptococci coverage is necessary.
- Minocycline
  - Skin and soft tissue infections
    - Minocycline Hydrochloride Oral capsule; Children 8 years and older and Adolescents: 4 mg/kg PO (Max: 200 mg) initially, then 2 mg/kg/dose PO every 12 hours (Max: 100 mg/dose). Clinical guidelines recommend 4 mg/kg PO (Max: 200 mg) initially, then 2 mg/kg/dose PO every 12 hours (Max: 100 mg/dose) for 5 to 10 days for CA-MRSA; add beta-lactam if beta-hemolytic streptococci coverage needed.
    - Minocycline Hydrochloride Oral capsule; Adults: 200 mg PO initially, then 100 mg PO every 12 hours; alternately, 100 to 200 mg PO initially, then 50 mg PO every 6 hours. Clinical guidelines recommend 200 mg PO initially, then 100 mg PO every 12 hours for 5 to 10 days for CA-MRSA; add beta-lactam if beta-hemolytic streptococci coverage needed.
Sulfonamide
- Trimethoprim-sulfamethoxazole
  - Skin and soft tissue infections
    - Sulfamethoxazole, Trimethoprim Oral tablet; Infants, Children, and Adolescents 2 months to 17 years: 4 to 6 mg/kg/dose (trimethoprim component) PO every 12 hours (Max: 320 mg trimethoprim/1,600 mg sulfamethoxazole/dose) for 5 to 10 days.
    - Sulfamethoxazole, Trimethoprim Oral tablet; Adults: 160 to 320 mg trimethoprim/800 to 1,600 mg sulfamethoxazole PO every 12 hours for 5 to 10 days.
Topical antibacterial
- Mupirocin
  - Impetigo
    - Mupirocin Topical ointment; Adults, Children, and Infants 2 months and older: Apply to affected area(s) 3 times daily for 1 to 2 weeks. May be covered with sterile gauze dressing. Reevaluate patients not showing clinical response in 3 to 5 days.
Adjunctive agents for combination therapy
- Rifamycin
  - Rifampin
    - Endocarditis
      - Due to Staphylococcus aureus in patients with prosthetic valves
        Rifampin Oral capsule; Infants, Children, and Adolescents: AHA recommends 20 mg/kg/day IV/PO in 3 equally divided doses and IDSA recommends 5 mg/kg IV/PO every 8 hours plus vancomycin for at least 6 weeks plus gentamicin for 2 weeks. Max: 900 mg/day.
        Rifampin Oral capsule; Adults: IDSA/AHA recommend 300 mg IV/PO every 8 hours plus vancomycin for at least 6 weeks plus gentamicin for 2 weeks.
      - Right-sided endocarditis secondary to Staphylococcus aureus in intravenous drug abusers
        Rifampin Oral capsule; Adults: Rifampin and ciprofloxacin have been studied x4 weeks; AHA recommends rifampin 900 mg/day PO in 3 divided doses and ciprofloxacin 1000 mg/day PO in 2 divided doses.
    - Bone and joint infections
      - Rifampin Oral capsule; Adults: 600 mg PO once daily or 300 to 450 mg PO every 12 hours for 3 months for hip infections or for 6 months for knee infections; use only in combination with another agent active against the pathogen.
- Aminoglycoside
  - Gentamicin
    - Endocarditis
      - Gentamicin Sulfate Solution for injection; Children and Adolescents: 1 to 2 mg/kg/dose IV every 8 hours recommended by guidelines; FDA-approved dosage = 2 to 2.5 mg/kg/dose IV/IM every 8 hours. Use in combination with appropriate antimicrobial agent depending on causative microorganism. Duration of therapy dependent on valve type and causative microorganism.
      - Gentamicin Sulfate Solution for injection; Adults: 3 mg/kg/day IV or IM in 1 dose, or alternately, divided every 8 hours, is recommended by guidelines. FDA-approved dosage is 3 mg/kg/day IV or IM divided every 8 hours for severe infections and 5 mg/kg/day IV or IM divided every 8 hours for life-threatening infections. Use in combination with appropriate antimicrobial agent depending on causative microorganism. Duration of therapy dependent on valve type and causative microorganism.

Nondrug and supportive care

Procedures

Incision and drainage

General explanation

Drainage of infected fluid through incision
Primary treatment for cutaneous abscess

Indication

Abscess

Contraindications

Larger abscesses must have adequate coagulation assurance
Relative contraindications:
- Abscesses on hands (excluding fingertips)
- Abscesses in the triangular area formed below the nose, above the lip, and between the nasolabial folds
- Breast abscesses near nipple or areola

Complications

Inadequate removal of infected material
Extending infected material into noninfected tissue

Removal of prosthesis or device and/or debridement

General explanation

Surgical removal of necrotic, infected soft tissue or bone to promote healing and prevent persistence or recurrence of infection
Removal of prosthetic material, when present, is recommended in most cases

Indication

Tissue destruction
Presence of infected prosthetic material

Contraindications

Medically unfit for anesthesia or surgery

Drainage of infected synovial fluid

General explanation

Infected synovial fluid should be removed by serial aspiration until dry, through arthroscopy or by open procedure
Arthroscopy and open surgery offer opportunity for debridement and irrigation

Indication

Septic native joint

Complications

Introduction of a different infecting organism

Comorbidities

Patients with devices that cannot be removed may require lifelong suppressive antibiotics
Patients undergoing cancer chemotherapy or hemodialysis often have very difficult vascular access, limiting options for removal and replacement of infected catheters

Special populations

Monitoring

Repeat blood cultures in all patients with bacteremia (including endocarditis) 2 to 4 days after initial positive and as needed thereafter until results become negative
Monitor vancomycin levels to assure adequate antibacterial activity and to avoid toxicity
- Obtain a trough level before the fourth or fifth dose; recommended level is 15 to 20 mcg/mL
- Repeat trough level at fourth dose after adjusting dose
- It is unclear whether or how often trough levels should be monitored once the desired level is achieved, but some authorities suggest weekly
- Repeated measurement is also prudent with changes in renal function or volume of distribution
Monitor platelet count if linezolid therapy lasts for more than 14 days
Monitor CBC, renal function, and creatine kinase level at least weekly during daptomycin therapy
Monitor gentamicin levels with third or fourth dose and then weekly to ensure appropriate dosing
- Recommended peak serum concentration is 2 to 3 mg/L
- Check renal function twice weekly

Complications

Complications may be related to site and severity of infection and to organism (MRSA versus MRSE)
- Skin and soft tissue infections usually resolve without complication; scarring may result from severe infections with tissue loss or abscesses requiring drainage (Related: Necrotizing soft tissue infections)
- Bacteremia (especially when due to MRSA) may result in severe complications:
  - Septic shock with multiorgan failure (Related: Sepsis)
  - Endocarditis
  - Secondary infection of implanted prostheses and devices
  - Other metastatic foci of infection (eg, abscesses of spleen, liver, kidneys, or brain; mycotic aneurysm)
- Complications of endocarditis due to either MRSA or MRSE are similar to those of bacteremia; in addition:
  - Valvular decompensation requiring valve replacement
  - Pulmonary edema
  - Embolization (eg, pulmonary embolism) (Related: Pulmonary embolism)
- Pneumonia
  - MRSA pneumonia may be fulminant, resulting in acute respiratory failure requiring mechanical ventilation (Related: Acute respiratory distress syndrome in adults)
    - Empyema
    - Deaths have been reported even in previously healthy people
- Bone and joint infections
  - Loss of function is the main complication; it may result from:
    - Decreased range of motion due to joint destruction
    - Arthrodesis (surgical joint fusion) or Girdlestone procedure (removal of hip joint without replacement); rarely done
    - Limb amputation
- Infection of cerebrospinal fluid shunt may result in loss of cognitive function or other neurologic deficits, especially in MRSA infections
- Dialysis-associated peritonitis may result in loss of access and/or scarring of the peritoneal membrane, necessitating a switch to hemodialysis, especially in MRSA infections
- Epidural abscess may result in neurologic deficits

Prognosis

Severe staphylococcal infections such as bacteremia, endocarditis, and pneumonia are associated with high morbidity and mortality
In a study of hospitalized patients with MRSA infection, the treatment failure rate and mortality for community-acquired MRSA infection were 23% and 16% respectively, and for hospital-acquired MRSA, they were 15% and 19%, respectively
Recurrence or relapse of infection is not unusual, especially with MRSA; MRSE infection associated with prosthetic material is difficult to eradicate and may relapse or recur
Up to 70% of patients with skin and soft tissue infections due to community-acquired MRSA develop recurrent infection within a year

Screening

At-risk populations

Not recommended in the general population
MRSA screening has been proposed, and in some areas is mandated, for hospital patients
- Universal screening of hospital patients is controversial
- Targeted screening is an alternative approach
  - In patients with identifiable risk factors based on epidemiology or medical history
  - High-risk settings (eg, ICU; preoperatively, especially if implantation of prosthetic material is anticipated)
- Identified patients may be cohorted or placed in isolation precautions, or decolonization may be attempted

Screening tests

Nasal swab for culture or nucleic acid amplification tests (eg, polymerase chain reaction) for MRSA

Prevention

Open or draining infections should be covered with a gauze dressing
Infection control in health care settings
- Standard precautions apply to all hospitalized patients, including those with MRSA or MRSE infections
  - Handwashing; gloves, masks/goggles, and gowns when indicated
- Contact precautions may be instituted
  - Isolation or cohorting; gowns and gloves on entering room for any contact with patient or surfaces; disposable or dedicated equipment
Decolonization
- A 5-day course of mupirocin nasal ointment, applied twice daily, is 90% effective in eradicating colonization short term, but long-term efficacy is only about 30% to 60%
- Chlorhexidine baths are also effective in decolonization and in preventing colonization; can be used in conjunction with mupirocin
- Whether decolonization is effective in preventing infection in all settings is not entirely clear, but a positive effect has been demonstrated in patients undergoing clean cardiothoracic and orthopedic surgery and in ICUs
- Decolonization has also been successful in reducing infections in athletes and may be helpful in breaking the cycle of recurrent skin and soft tissue MRSA infections in individual patients or households

Sources

Cosgrove SE et al: Management of methicillin-resistant Staphylococcus aureus bacteremia. Clin Infect Dis. 46(suppl 5):S386-93, 2008 Reference

10 Interesting Facts of Methicillin Resistant Staphylococcus Infections

Classification

History

Physical examination

Causes and Risk Factors

Causes

Risk factors and/or associations

Age

Ethnicity/race

Other risk factors/associations

How is Methicillin Resistant Staphylococcus Infections diagnosed?

Laboratory

Imaging

Procedures

Thoracentesis

General explanation

Indication

Contraindications

Complications

Interpretation of results

Arthrocentesis

General explanation

Indication

Contraindications

Complications

Interpretation of results

Lumbar puncture (or alternative means of obtaining cerebrospinal fluid from a shunt or indwelling device)

General explanation

Indication

Contraindications

Complications

Interpretation of results

Analysis of peritoneal dialysate

General explanation

Indication

Interpretation of results

Bone biopsy

General explanation

Indication

Interpretation of results

Debridement of surgical wound

General explanation

Indication

Interpretation of results

Bronchoscopy

General explanation

Indication

Contraindications

Complications

Interpretation of results

Differential Diagnosis

Most common

Treatment Goals

Admission criteria

Criteria for ICU admission

Recommendations for specialist referral

Treatment Options

Drug therapy

Nondrug and supportive care

Procedures

Incision and drainage

Removal of prosthesis or device and/or debridement

Drainage of infected synovial fluid

Comorbidities

Monitoring

Complications

Prognosis

Screening

At-risk populations

Screening tests

Prevention

Sources

Share this:

Like this:

Related Posts

Related Posts:

Recent Post

features

Categories

Weekly Newsletter