Chronic Diarrhea Associated with Vibrio alginolyticus in an Immunocompromised Patient

MacConkey agar. Biochemical testing revealed that the organism was oxidase-, catalase-, and nitrate-positive, and it was capable of growth at 42°C. The isolate oxidized but did not ferment glucose and did not utilize xylose, mannitol, sucrose, maltose, or lactose. It did not reduce nitrate or split urea, and the indole test was negative. The lysine, arginine, and ornithine enzymatic reactions were negative. Results of clinical laboratory testing of the strain isolated from our patient were consistent with the growth and biochemical patterns established by the CDC for CDC Group O1 organisms [1]. By microtiter dilution testing, the strain was found to be susceptible to piperacillin, ceftazidime, ceftizoxime, ciprofloxacin, chloramphenicol, amikacin, imipenem, ticarcillin/clavulanic acid, and ampicillin/sulbactam but resistant to aztreonam. This case represents the first report of the CDC Group O1 bacterium as the etiologic agent of necrotizing aspiration pneumonia. The development of this pneumonia appears to have followed the witnessed aspiration event; therefore, we speculate that the source of this microorganism was either oropharyngeal or gastrointestinal flora. Although the pneumonia may have been the product of a polymicrobial infection, no other organisms other than CDC Group O1 bacteria were isolated from cultures of specimens collected at the time of the initial febrile episode. The CDC has received 62 different clinical isolates of this organism from various sources. The sources are quite diverse and include blood (55% of isolates), CSF (6%), pleural fluid (6%), wound (5%), cervix (5%), and other sites (23%), including vagina, heart valves, lymph nodes, eye, intravenous fluid, platelets, sternum, scapula, finger, bone marrow, peritoneal fluid, allergenic extract, a water bath, and “unknown” [1]. Although the invasive potential for this organism is obvious, no clinical data have appeared in the literature, and the clinical significance of these isolates is unknown. This report suggests that this bacillus is invasive enough to cause necrotizing pneumonia with complicating bronchopleural fistula and bacteremia. Therapy consisted of simple local drainage as well as dual antimicrobial treatment directed by the reported susceptibility patterns of the isolate. A broad pattern of susceptibility to antibiotics was apparent, but we would recommend dual therapy for infections with the CDC Group O1 bacterium on the basis of occasional recalcitrance of syndromes caused by similar nosocomial gramnegative rods [2].