What are the causes and treatments of prostatitis?

Causes of Prostatitis

Bacterial Causes

Gram-negative bacteria cause 80-97% of acute bacterial prostatitis cases, with Escherichia coli being the predominant pathogen, followed by Klebsiella pneumoniae, Pseudomonas aeruginosa, Proteus mirabilis, Enterobacter species, and Serratia marcescens. 1, 2

Acute Bacterial Prostatitis Pathogens

• Gram-negative organisms account for the vast majority of cases, including:

  • Escherichia coli (most common) 1, 2
  • Klebsiella pneumoniae 1, 2
  • Pseudomonas aeruginosa 1, 2
  • Proteus mirabilis 1
  • Enterobacter species 1
  • Serratia marcescens 1

• Gram-positive bacteria cause a minority of cases but include:

  • Staphylococcus aureus 1
  • Enterococcus species (particularly E. faecalis) 1, 3
  • Group B streptococci 1
  • Staphylococcus saprophyticus (rare but documented) 4

Chronic Bacterial Prostatitis Pathogens

• Up to 74% of chronic bacterial prostatitis cases are caused by gram-negative organisms, predominantly E. coli, with other pathogens including Proteus mirabilis, Enterobacter species, and Serratia marcescens. 1, 2

• Atypical pathogens require specific consideration and testing:

  • Chlamydia trachomatis 1, 5
  • Mycoplasma species 1, 5

Pathogenic Mechanisms

• Bacterial isolates causing acute prostatitis are highly virulent strains with multiple virulence factors, and the ability to form biofilms may facilitate progression to chronic bacterial prostatitis. 6

• In up to 90% of cases, pathogens migrate from the urethra or bladder to cause infection. 7

Non-Bacterial Causes

Fewer than 10% of prostatitis cases are confirmed to have bacterial infection, meaning the majority represent chronic prostatitis/chronic pelvic pain syndrome (CP/CPPS), which is not caused by culturable infectious agents. 1, 2

Chronic Prostatitis/Chronic Pelvic Pain Syndrome

• CP/CPPS is the most prevalent form of prostatitis and is not frequently caused by a culturable infectious agent, requiring different management focused on symptom relief rather than antimicrobials. 1, 8

• This form may represent a neuromuscular disorder or pain syndrome rather than infection, and can respond to non-prostate-centered treatments such as physical therapy, myofascial trigger point release, and relaxation techniques. 8

Clinical Progression Patterns

• Approximately 10% of acute bacterial prostatitis cases progress to chronic bacterial prostatitis, and another 10% develop into chronic pelvic pain syndrome. 6

• Untreated or inadequately treated bacterial prostatitis typically progresses rather than resolves spontaneously, with premature antibiotic discontinuation leading to chronic infection. 3

Key Diagnostic Considerations

• Midstream urine culture can identify the causative organism in acute bacterial prostatitis, while the Meares-Stamey 4-glass test (or simplified 2-specimen variant) is the gold standard for diagnosing chronic bacterial prostatitis, requiring a 10-fold higher bacterial count in expressed prostatic secretions compared to midstream urine. 1, 5

• Prostatic massage must be avoided in acute bacterial prostatitis due to risk of bacteremia, and digital rectal examination should be performed gently. 7, 1, 5