Chronic Diarrhea and Weight Loss Due to Vibrio parahaemolyticus Infection in a Renal Transplant Recipient

Our patient was a 57-year-old male who received a cadaveric renal transplant seven years earlier, on cyclosporine A (CyA) and mycophenolate mofetil (MMF). He presented with an eight-week history of abdominal pain, watery diarrhea without blood or mucus, nausea, and vomiting. He also reported fatigue, reduced appetite, and weight loss of 8 kg over four months. During that period, he had six similar episodes requiring intravenous fluid replacement and monitoring of graft function and CyA levels. Stool specimens on these occasions were negative for bacterial pathogens and viruses; no ova, parasites, or Cryptosporidia were detected. Tests for cytomegalovirus (CMV) and Ebstein-Barr virus infection and a vasculitic screen were also negative. Stool specimens during this admission were watery with no blood and very little mucus. Microscopy showed the presence of fecal leukocytes. Concentration methods showed no ova, cysts, or parasites; Ziehl-Neelsen stains for Cryptosporidia were negative. Cultures for Salmonella, Shigella, E. coli O157, Campylobacter and Yersinia were negative on three occasions. Upper GI endoscopy showed a small (3 mm) duodenal ulcer and H. pylori associated gastritis. Anti-CMV antibody staining was negative. A small bowel Gastrografin study showed no mucosal abnormalities. Colonoscopy identified a 3 cm polyp (tubular adenoma) in the rectum, which was subsequently excised. CT abdomen showed no bowel or solid organ lesions and no evidence of an active inflammatory process in the bowel. A detailed travel history revealed a visit to the Middle East (Beirut) six months prior to admission, with frequent seafood intake during that visit. Enteric infection with a Vibrio species was suspected and stool specimens were cultured on media designed to recover them (thiosulphate citrate bile salt sucrose agar following alkaline peptone enrichment). Vibrio parahaemolyticus sensitive to tetracycline was isolated. The patient was treated with doxycycline 100 mg once a day for five days leading to complete resolution of symptoms. Vibrio parahaemolyticus, a halophilic, salt-loving, gram-negative bacterium is ubiquitous in warm coastal waters of the temperate and tropical regions (1). V. parahaemolyticus is a major cause of foodborne disease in the Far East, responsible for up to 35% of all diarrheal illnesses. Consumption of raw or undercooked shellfish is the most common means of acquiring V. parahaemolyticus infection (2). Raw oysters (3), mussels, and fish (4) are often implicated. Enteric infection with V. parahaemolyticus can range in severity from mild watery diarrhea to a frank dysentery-like syndrome. A watery diarrhea is the most common presentation, usually self-limiting, resolving within 3 to 4 days. Other associated symptoms include nausea, vomiting, and mild to moderately severe cramping abdominal pain. Antibiotic therapy has not been shown to improve symptoms or reduce duration of carriage (3). Enterotoxigenic or cytotoxic substances produced by V. parahaemolyticus inducing an inflammatory reaction in the small bowel are possible pathogenic mechanisms (3). A thermostable direct hemolysin (TDH), a serine protease (virulence factor) and a capsular polysaccharide (CPS) are also implicated. Our patient’s unusual presentation with a long duration of symptoms, and the initial delay in the identification of the pathogen, underline the importance of taking a detailed travel and food history and of close cooperation between clinician and microbiologist. Our experience, the first reported case of infection with Vibrio parahaemolyticus causing prolonged diarrhea in a transplant recipient, shows that infections with enteropathogenic organisms, which are self-limiting in the immunocompetent, can give rise to protracted symptoms in the immunocompromised. Venugopal K. Shankar Miguel Zilvetti Ashok Handa Ian C.J.W. Bowler Derek W.R.