Distribution of Virulence Factors and Molecular Fingerprinting of Aeromonas Species Isolates from Water and Clinical Samples: Suggestive Evidence of Water-to-Human Transmission

A total of 227 isolates ofAeromonas obtained from different geographical locations in the United States and different parts of the world, including 28 reference strains, were analyzed to determine the presence of various virulence factors. These isolates were also fingerprinted using biochemical identification and pulse-field gel electrophoresis (PFGE). Of these 227 isolates, 199 that were collected from water and clinical samples belonged to three major groups or complexes, namely, theA. hydrophila group, theA. caviae-A. media group, and theA. veronii-A. sobria group, based on biochemical profiles, and they had various pulsotypes. When virulence factor activities were examined,Aeromonas isolates obtained from clinical sources had higher cytotoxic activities than isolates obtained from water sources for all threeAeromonas species groups. Likewise, the production of quorum-sensing signaling molecules, such asN -acyl homoserine lactone, was greater in clinical isolates than in isolates from water for theA. caviae-A. media andA. hydrophila groups. Based on colony blot DNA hybridization, the heat-labile cytotonic enterotoxin gene and the DNA adenosine methyltransferase gene were more prevalent in clinical isolates than in water isolates for all threeAeromonas groups. Using colony blot DNA hybridization and PFGE, we obtained three sets of water and clinical isolates that had the same virulence signature and had indistinguishable PFGE patterns. In addition, all of these isolates belonged to theA. caviae-A. media group. The findings of the present study provide the first suggestive evidence of successful colonization and infection by particular strains of certainAeromonas species after transmission from water to humans.