Which are the common infecting organisms in UTI?
Escherichia coli is isolated in 80% to 85% of episodes of acute cystitis and 85% to 90% of episodes of acute uncomplicated pyelonephritis.
Uropathogenic E. coli are characterized by the expression of diverse virulence factors including adhesins, iron sequestration systems, and toxins.
Pyelonephritis is consistently associated with expression of the P pilus, a Gal-∝(1-4), Gal-β disaccharide galabiose adhesin. Staphylococcus saprophyticus, a coagulase negative staphylococcus, is isolated from 5% to 10% of cystitis episodes. It is virtually only identified as a pathogen in acute cystitis.
A greater variety of organisms are isolated from complicated urinary infection. E. coli remains an important pathogen, but Klebsiella pneumoniae, Citrobacter spp., Proteus mirabilis, Pseudomonas aeruginosa, Enterococcus spp., and other bacteria or yeast are also isolated. These bacteria are more likely to be resistant to antimicrobials.
This is attributed to prior antimicrobial exposure or the acquisition of health care–associated organisms following urologic interventions.
Urease-producing organisms, such as P. mirabilis, Morganella morganii, and Providencia stuartii , are common in the biofilm on indwelling devices.
