Which statement about urinary tract infection risk is true?

• A. Escherichia coli is the most common pathogen
• B. UTIs are more common in males
• C. Spermicidal use reduces risk
• D. Postmenopausal status eliminates risk

Answer: (A)

The main idea here is that most urinary tract infections are caused by bacteria originating from the gut, with Escherichia coli responsible for the vast majority of cases. E. coli strains that cause UTIs have virulence factors, such as adhesins (P fimbriae), that help them stick to and invade the urinary tract lining, enabling ascent from the periurethral area into the bladder and potentially the kidneys. This explains why E. coli is the most common pathogen across different populations and why factors that bring bacteria closer to the bladder increase risk.

UTIs are more common in females because the female urethra is shorter and closer to the anus, making bacterial transfer to the bladder easier. Spermicidal use disrupts vaginal flora and often increases colonization by pathogenic E. coli, raising risk rather than reducing it. Postmenopausal status does not eliminate risk; estrogen deficiency can alter the vaginal microbiome and mucosal defenses, increasing susceptibility, though topical estrogen can help reduce risk in some women.

So, the statement that Escherichia coli is the most common pathogen is true.