A search for plasmid-mediated phenomena associated with the pathogenicity of Yersinia enterocolitica and Vibrio parahaemolyticus

Abstract

Vibrio parahaemolyticus and Yersinia enterocolitica are two recently recognized enteric pathogens. Each of these species consists of pathogenic and non-pathogenic biotypes. At the present time, there is no reliable method for distinguishing pathogenic strains from non-pathogenic strains for either of these species. In this study, strains of V. parahaemolyticus were tested for pathogenicity using the rabbit ligated ileal loop test, Kanagawa reaction, rabbit back skin test for vascular permeability, and suckling mouse test for heat-stable enterotoxin. Strains of Y. enterocolitica were tested for pathogenicity using the Sereny test for tissue-invasiveness, Y1 adrenal cell assay for heat-labile enterotoxin, and suckling mouse test for heat-stable enterotoxin. Strains of V. parahaemolyticus and Y. enterocolitica were also tested for susceptibility to antibiotics. In addition, each strain of V. parahaemolyticus and Y. enterocolitica was examined for the presence of plasmid DNA by agarose gel electrophoresis. The results of the tests for pathogenicity and antibiotic susceptibility were compared to the plasmid DNA content of each strain, in an effort to identify plasmid-mediated factors that are associated with pathogenicity and/or antibiotic resistance in these species. The results of this comparison indicate that the Kanagawa hemolysis of V. parahaemolyticus is not plasmid-mediated. Other factors that might be associated with the pathogenicity of V. parahaemolyticus (ileal loop reaction, vascular permeability factors, and heat-stable enterotoxins) were also not plasmid-mediated..