Research Day

Aeromonas Hydrophila as a Cause of Chronic Diarrhea

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Introduction: Aeromonas hydrophilia is an uncommon human pathogen which is a rare cause of gastroenteritis. The modern era of molecular diagnostics have produced broad spectrum nucleic acid based screening panels for viral, bacterial, fungal and protozoan pathogens that may cause infection. We present a case of Aeromonas-associated chronic colitis that was identified on standard microbiologic culture but was not found using a broad gastroenteritis molecular screening as the organism is not part of the screening. Case Report: A 63 year old woman with a history of hepatitis C-associated cirrhosis was admitted with a 4 week history of watery diarrhea. She lived in a semirural environment using well water. An out-patient evaluation produced a stool culture positive for A. hydrophilia sensitive to trimethoprim/sulfamethoxazole (SXT) and ciprofloxacin and she was treated with SXT without response. After several more weeks of watery diarrhea without blood or mucous and without constitutional symptoms, the patient was admitted for further workup. Two additional stool cultures revealed A. hydrophilia, blood cultures were negative and a stool molecular marker screening panel was negative including the viral causes of diarrhea and the E. coli enteropaths but not Aeromonas. C. difficile was negative as was stool ova and parasite assay and colonoscopy revealed erythema, small ulcers covered with a purulent discharge. Pathology suggested chronic colitis. Ciprofloxacin was administered which caused disappearance of the diarrhea and clearance of the A. hydrophilia in the stool. Conclusion: Aeromonas hydrophilia is a fresh water Gram negative bacillus associated with skin and soft tissue infection and is a rare cause of enteric infection in man which can be persistent in nature. This report underscores that enteric infection can be persistent and that the modern DNA diagnostic batteries to diagnose infections in the respiratory and gastrointestinal tracts can be false negative if the organism is not part of the panel.

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