Chronic bacterial prostatitis (CBP) represents a bacterial infection of the prostate gland. CBP causes an associated symptom complex, the hallmark of which is the occurrence of relapsing urinary tract infections, usually involving the same pathogen. CBP is often confused withnonbacterial prostatitis, chronic pelvic pain syndrome (CPPS), and prostatodynia.

By definition, this condition is characterized by bacterial growth in culture of the expressed prostatic fluid, semen, or postmassage urine specimen. The expressed prostatic secretion (EPS) usually contains more than 10 white blood cells (WBCs) per high-power field (hpf) and macrophages

The prostatitis symptom complex is very common. Approximately half of all men eventually develop symptoms consistent with prostatitis. This symptom complex accounts for approximately 25% of urologic evaluations in men, or approximately 8% of all urology visits. In fact, the patient appointments for prostatitis outnumber those for cancer or benign prostatic hyperplasia (BPH). ^[1] (See Epidemiology and Presentation.)

Although the prostatitis symptom complex is not always caused by a bacterial infection, traditional teaching states that bacteria are the cause and require an antibiotic for treatment. This may explain why 50% of the patients with symptoms consistent with CBP are treated with antibiotics, yet only 5-10% of the men actually have a true bacteriologic condition that improves with treatment. Nonetheless, symptom improvement may also be due to a placebo effect or to an anti-inflammatory effect conferred by the antibiotic itself. (See Treatment and Medication.) 

A confounding factor is that fastidious organisms (eg, Chlamydia trachomatis, Ureaplasma urealyticum, Mycoplasma hominis) can cause prostatitis but do not grow in standard culture conditions; therefore, the condition may be interpreted as nonbacterial prostatitis. Continuing research, using sophisticated research methods, further elucidates that bacterial infection is the cause for more cases of prostatitis. Results from studies show that identification of bacterial ribosomal ribonucleic acid (rRNA), by a reverse transcriptase–polymerase chain reaction (RT-PCR) assay, assists in predicting a successful response to antibiotic treatment in patients with chronic prostatitis.

Continued research of occult bacterial infections as the cause of prostatitis syndrome is ongoing and will lead to further effective treatments for prostatitis symptoms.

Studies have shown a possible association between prostate cancer and prostatitis.  Anti-inflammatory agents that target cyclooxygenase are hypothesized to decrease this risk.

NIH classification of prostatitis

Based on specific etiologies, the National Institutes of Health (NIH) classified the various forms of prostatitis in 1995. ^{[5, 2]} Type II is CBP, the focus of this article.

Type I is acute bacterial prostatitis, which is a well-defined infectious disease of the lower urinary tract. It is a bacterial infection, most commonly with E coli. Patients frequently present with bacteremia

The most common type of prostatitis (90% of cases) is type III, the CPPS category. Type III is chronic abacterial prostatitis (inflammatory CPPS and noninflammatory CPPS). It is nonbacterial in origin. Diagnosis is made on the basis of expressed prostatic secretion (EPS) findings, clinical findings, and culture results. An empiric trial of antimicrobials is usually warranted (fluoroquinolone or trimethoprim-sulfamethoxazole [TMP-SMZ]). ^[6]

Type IV is asymptomatic inflammatory prostatitis. It is often diagnosed based on results of biopsies, surgical specimens, or semen analysis obtained for other reasons. No treatment is warranted. Biopsy is typically indicated because of an elevated prostate-specific antigen (PSA) level.