The organism most commonly isolated in community-acquired uncomplicated cystitis is which?

The organism most commonly isolated in community-acquired uncomplicated cystitis is which?

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

Answer: (B)

In community-acquired uncomplicated cystitis, Escherichia coli is by far the most common cause because it lives in the gut and has evolved traits that let it reach and cling to the urinary tract. Its fimbriae, including P and type 1 fimbriae, promote strong adhesion to the urothelium, so the bacteria can attach despite urine flow. It can also invade bladder cells and form reservoirs, which helps it persist and cause infection in otherwise healthy individuals. These abilities, combined with its ubiquitous presence in the intestinal flora, explain why E. coli accounts for the vast majority of such UTIs. Enterobacter aerogenes, Klebsiella pneumoniae, and Proteus vulgaris can cause urinary infections, but they are less common in healthy, community-dwelling patients with uncomplicated disease and are more often associated with healthcare-associated or complicated infections.

In community-acquired uncomplicated cystitis, Escherichia coli is by far the most common cause because it lives in the gut and has evolved traits that let it reach and cling to the urinary tract. Its fimbriae, including P and type 1 fimbriae, promote strong adhesion to the urothelium, so the bacteria can attach despite urine flow. It can also invade bladder cells and form reservoirs, which helps it persist and cause infection in otherwise healthy individuals. These abilities, combined with its ubiquitous presence in the intestinal flora, explain why E. coli accounts for the vast majority of such UTIs.

Enterobacter aerogenes, Klebsiella pneumoniae, and Proteus vulgaris can cause urinary infections, but they are less common in healthy, community-dwelling patients with uncomplicated disease and are more often associated with healthcare-associated or complicated infections.