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Chronic bacterial prostatitis is commonly caused by Escherichia coli and is less frequently caused by Klebsiella pneumoniae, Enterobacter, Proteus mirabilis, and enterococci (6). Reported rare causes of prostatitis include Candida species, Blastomyces dermatitidis, Histoplasma capsulatum, Mycobacterium tuberculosis, and nontuberculous mycobacteria (8). We report the first case, to our knowledge, of chronic prostatitis due to Yersinia pseudotuberculosis.

A 55-year-old man had been suffering from recurrent urinary tract infections over the last 3 years. No prophylactic antibiotic treatment was administered. The pathogen was frequently E. coli, and in two cases it was K. pneumoniae. Findings from an intravenous pyelogram and abdominal ultrasound were unremarkable. In the last months preceding his referral to our center, he had three successive urinary tract infections due to Y. pseudotuberculosis.

Cultures of urethral urine, midstream urine, and prostatic secretions expressed by massage yielded heavy growth of Y. pseudotuberculosis from the last site and slight growth from the first two sites. Microscopic examination of the expressed prostatic secretions showed approximately 30 leukocytes per high-power field. Stool cultures did not grow Yersinia species. Prophylactic treatment with trimethoprim-sulfamethoxazole gave satisfactory results: the patient was free of symptoms, with negative urinary cultures.

The most common manifestation of Y. pseudotuberculosis infection in humans is mesenteric lymphadenitis accompanied by abdominal pain and fever (9). A septicemic form, occurring predominantly in patients with diabetes, hepatic cirrhosis, malignancy, and iron overload, has occasionally been described (5). Reported rare "atypical" manifestations of Y. pseudotuberculosis infection include interstitial nephritis (2), suppurative lymphadenitis (7), erythema nodosum, and nonsuppurative arthritis (1). To our knowledge, only one case of urinary tract infection due to Y. pseudotuberculosis has been reported (3). Our case is the first reported case of prostatitis due to Y. pseudotuberculosis.

Epidemiologically, we could not identify any environmental risk factors that might be responsible for the patient's illness. Though several stool cultures did not yield Yersinia species, the feco-oral route is probably the main mode of acquisition, as with other enteric infections (4).