genitourinary disorders
Bacterial Urinary Tract Infections
Etiology of Bacterial UTIs
The bacteria that most often cause Cystitis and Enteric, usually gram-negative aerobic bacteria (most often) Gram-positive bacteria (less often) In normal genitourinary tracts,strains ofEscherichia coliwith specific attachment factors for transitional epithelium of the bladder and ureters account for 75 to 95% of cases. The remaining gram-negative urinary pathogens are usually other enterobacteria, typicallyKlebsiellaorProteus mirabilis, and occasionallyPseudomonas aeruginosa. Among gram-positive bacteria,Staphylococcus saprophyticusis isolated in 5 to 10% of bacterial UTIs. Less common gram-positive bacterial isolates areEnterococcus faecalis(group D streptococci) andStreptococcus agalactiae(group B streptococci), which may be contaminants, particularly if they were isolated from patients with uncomplicated cystitis. In hospitalized patients,E. coliaccounts for about 50% of cases. The gram-negative speciesKlebsiella,Proteus,Enterobacter,Pseudomonas, andSerratiaaccount for about 40%, and the gram-positive bacterial cocciE. faecalis,S. saprophyticus, andStaphylococcus aureusaccount for the remainder. 