Gram negative bacteria are the most common cause of prostatitis. E.coli is most frequent followed by Klebsiella, proteus and (less commonly) Pseudomonas, eterobacter species and serratia marcescens. Prostate infection is commonly associated with a UTI and may serve as a reservoir for recurrent UTIs. With the exception of enterococci, gram positive pathogens are uncommon. Cases of staphylococcus species prostatitis have also been reported. The cause of culture negative prostatitis has not been clarified. Chalmydia is a possible cause in these cases.
The mechanism by which bacteria usually reaches the prostate is reflux of infected urine. The prostate contains a potent antibacterial substance called prostatic antibacterial factor. The production of this zinc containing compound is markedly reduced during prostatitis, allowing active growth of bacteria. Infection results in an influx of PMNs edema, intraductal desquamation and cell necrosis.
Patients with acute bacterial prostatitis experience fever, chills, dysuria, and urinary frequency. If the prostate becomes extremely swollen, bladder outlet obstruction may develop. On physical examination, the patient often appears septic and has a high fever. Moderate tenderness of the suprapubic region is often seen. On rectal exam, the prostate is exquisitely tender and difusely enlarged.
In chronic prostatitis, symptoms may be subtle. Back pain, low grade fever, myalgias, and arthralgias are the most common complaints. These patients often present with recurrent UTIs.
In acute bacterial prostatitis, massage of the inflamed prostate is contraindicated because of a high risk of precipitating bacteremia. The causative agent can usually be identified by urine culture. Blood cultures may also prove to be positive. Diagnosis and treatment of chronic prostatitis is difficult, and is best managed by an experienced urologist. Quantitative culturing of the first void urine midstream urine, and prostatic massage sample or post prostatic massage urine sample are recommended to differentiate cystitis and urethritis from chronic prostatitis.
Initial empiric therapy for acute bacterial prostatitis should include coverage for Enterobacteriaceae. Ciprofloxacin or TMP-SMX in specific doses are recommended for prostatitis treatment. Once the culture result is available prostatitis treatment can be modified. Therapy should be prolonged: four to six weeks. It should be kept in mind that most antibiotics do not penetrate the lipophilic, acidic environment of the prostate; however, just as is observed in meningitis, the marked inflammation in acute prostatitis allows for antibiotic penetration. Patients usually respond quickly to intravenous therapy, allowing the switch to an oral regimen.
In chronic prostatitis, antibiotic penetration is critical for effective prostatitis treatment. Trimethoprim is lip soluble and readily penetrates the prostate. The fluroquinolones have also proved effective for treatment of chronic Prostatitis. Treatment must be very prolonged. Therapy with oral TMP-SMX (1 double strenght tablet twice daily) or fluoroquinolone (ciprofloxacin 500 mg twice daily) should be continued for six to 12 weeks. Relapse are frequent and prostatectomy may be required for cure.