Acute prostatitis in men older than 35 is most commonly caused by which organism, compared to younger men?

• A. Chlamydia & Gonorrhea
• B. Proteus
• C. Klebsiella
• D. E. coli

Answer: (D)

Age-related shifts in the typical pathogens of acute bacterial prostatitis are key here. In men over 35, infection is most commonly caused by Escherichia coli, a common urinary tract pathogen that often ascends into the prostatic ducts. This contrasts with younger, sexually active men, where infections from sexually transmitted organisms such as Chlamydia trachomatis or Neisseria gonorrhoeae are more typical. While other Gram-negative rods like Proteus or Klebsiella can cause prostatitis, Escherichia coli remains the most frequent offender in this older group, making it the best answer.