Which organism is a common etiologic agent of community-acquired uncomplicated cystitis?

• A. Escherichia coli
• B. Enterobacter aerogenes
• C. Klebsiella pneumoniae
• D. Proteus vulgaris

Answer: (A)

Uncomplicated cystitis acquired in the community is most commonly caused by uropathogenic Escherichia coli. This organism is a normal inhabitant of the gut and can easily ascend from the urethra to the bladder. Its virulence factors, including adhesins such as P fimbriae, promote robust binding to bladder lining and establish infection efficiently. Because E. coli accounts for the vast majority of cases in otherwise healthy individuals, it stands out as the leading etiologic agent for this condition. The other organisms listed can cause UTIs as well, but they are much less common in community-acquired, uncomplicated cystitis and are more often implicated in healthcare-associated infections or complicated scenarios.