Blood Stream Infections Due to Aeromonas Species: A Retrospective Analysis of 24 Cases at a Tertiary Hospital in Okinawa and Previous Related Literature Review in Japan

Background: Although overseas literature on bacteremia due to Aeromonas species have been increasing, only 4 English articles have been reported from Japan in the past. The etiology of Aeromonas species in bacteremia in Japanese patients is poorly understood. The aim of this study was to determine the clinical and microbiological characteristics of Aeromonas bacteremia in Japan.

Methods: The medical records of patients with Aeromonas bacteremia diagnosed in University of the Ryukyus Hospital from January 2000 to April 2016 were reviewed. Identification and susceptibility testing of the strains were performed by the RAISUS automated method (Nissui Pharmaceuticals Co., Ltd., Tokyo). Voges-Proskauer test was also conducted in order to distinguish between Aeromonas hydrophila and Aeromonas caviae. We also reviewed 49 Aeromonasbacteremic patients in four literature investigated in Japan.

Results: Twenty-four cases were encountered at our institution (20 cases with A. hydrophila, 2 with A. caviae, and 2 with A. veronii biovar sobria bacteremia) during the 16-years study period. The median age of patients was 69 years (range: 17–92) and the majority were men (17/24; 70.8%). Sixteen patients (66.8%) had gastrointestinal manifestation such as diarrhea, vomit, and abdominal pain, and 15 (63%) had jaundice. Bacteremia occurred most often in patients with disease of the hepatobiliary or pancreatic system (45.8%; including 5 pancreatic cancer, 2 cholangiocarcinoma, 2 gallbladder tumor, and 2 liver cirrhosis) and gastrointestinal cancer (16.7%). According to our literature review including our 24 cases, the most frequent pathogen isolated was A. hydrophila (44/73; 60.3%). There was 25 patients (34.2%) with polymicrobial Aeromonas bacteremia and community-acquired blood stream infections due to Aeromonasspecies occurred in 51.6% patients. The overall 30-day mortality was 28.8%.

Conclusion: Our results indicated that the most common significant risk factors for Aeromonas bacteremia were solid tumor and complication associated with liver, biliary tract, and pancreas. Clinicians should be aware that Aeromonas blood stream infections often occurred as polymicrobial bacteremia, nearly 50% patient exhibit septic shock and have a high fatality rate.