Recurrent salmonella infection with a single strain in the acquired immunodeficiency syndrome. Confirmation by plasmid fingerprinting.

Five weeks before the development of acquired immunodeficiency syndrome (AIDS), a 38-yr-old homosexual man had symptomatic gastroenteritis that resolved without antibiotic treatment. His stool culture was positive for Salmonella typhimurium at that time. The patient subsequently developed Pneumocystis carinii pneumonia and received a 10-day course of intravenous trimethoprim-sulfamethoxazole. He developed salmonella bacteremia 4 months later. The salmonella isolates from the stool and blood were susceptible to trimethoprim-sulfamethoxazole. Comparison of cryptic plasmids showed a pattern identical to the initial salmonella infection, so infection with a new strain did not cause the bacteremia. This finding illustrates the utility of plasmid fingerprinting as a diagnostic tool, and suggests that persons with AIDS, or those at high risk with prodromal symptoms, should receive prompt, effective therapy for nontyphoidal salmonella gastroenteritis.