What causes prostatitis in men?

How Men Develop Prostatitis

Men develop prostatitis primarily through ascending urethral or bladder infection (90% of cases), with gram-negative bacteria—especially Escherichia coli—causing 80-97% of acute bacterial cases and up to 74% of chronic bacterial cases. 1, 2, 3

Bacterial Pathogenesis and Routes of Infection

Primary Mechanism: Ascending Infection

• In up to 90% of cases, pathogens migrate from the urethra or bladder to cause prostatic infection, establishing the urinary tract as the primary source. 2
• Gram-negative bacteria dominate acute bacterial prostatitis, including E. coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, Enterobacter species, and Serratia marcescens. 1, 2, 3
• Gram-positive organisms (Staphylococcus aureus, Enterococcus species, Group B streptococci) account for the remaining bacterial cases. 1, 2

Chronic Bacterial Prostatitis Development

• Up to 74% of chronic bacterial prostatitis cases result from persistent gram-negative organisms, particularly E. coli, that establish biofilms within prostatic tissue. 2, 3
• Recurrent urinary tract infections with the same bacterial strain characterize chronic bacterial prostatitis, indicating failure to eradicate the prostatic reservoir. 3, 4

Non-Bacterial Causes and Risk Factors

Sexually Transmitted Pathogens

• In men under 35 years, sexually transmitted organisms (Chlamydia trachomatis, Neisseria gonorrhoeae, Mycoplasma species) can cause prostatitis through urethral ascent. 1
• These atypical pathogens require specific microbiological evaluation with nucleic acid amplification testing (NAAT) rather than standard urine cultures. 1

Chronic Prostatitis/Chronic Pelvic Pain Syndrome (CP/CPPS)

• CP/CPPS, affecting 9.3% of men lifetime, is not caused by culturable infectious agents in most cases. 2, 3
• The pathogenesis likely involves an initial infectious or inflammatory trigger that causes neurological injury, eventually resulting in pelvic floor dysfunction with increased muscle tone. 4
• Fewer than 10% of all prostatitis cases have confirmed bacterial infection, making CP/CPPS the predominant form. 2, 3

Clinical Pitfalls and Diagnostic Considerations

Critical Examination Precautions

• Prostatic massage must be avoided in acute bacterial prostatitis due to bacteremia risk, and digital rectal examination should be performed gently only. 1, 2
• Vigorous prostatic manipulation can precipitate systemic infection in acute cases. 2

Distinguishing Bacterial from Non-Bacterial Disease

• The Meares-Stamey 4-glass test (or 2-specimen variant) definitively diagnoses bacterial prostatitis by demonstrating a 10-fold higher bacterial count in expressed prostatic secretions versus midstream urine. 1, 2, 5
• Without documented urinary tract infections from uropathogens, patients likely have CP/CPPS rather than bacterial disease, fundamentally changing management from antibiotics to symptom-directed therapy. 4

Healthcare-Associated Infections

• Patients with recent catheterization, instrumentation, or healthcare exposure may harbor multidrug-resistant organisms including Enterococcus faecalis and carbapenem-resistant Enterobacterales. 2, 6
• Specimens from indwelling catheters frequently contain colonizing flora due to rapid biofilm formation and do not represent true infection. 1