PLASMIDS AND AEROMONAS VIRULENCE

Most putative virulence determinants of Aeromonas species are chromoso mally encoded. However, several recent reports have indicated that som e may be carried on or regulated by plasmids. Therefore, we examined t he plasmid carriage rate of a total of 140 clinical and environmental Aeromonas isolates. Plasmid carriage was compared with the ability of an isolate to produce toxins and adhere to HEp-2 cells. Overall, plasm id incidence in Aeromonas species was low (23/140, 16%) and independen t of the source of the isolate. Plasmids were, however, more common in environmental isolates of A. veronii biovar sobria than in clinical i solates of this species (P < 0.05). We could fmd no evidence to suppor t the recent literature findings that plasmids may have a role in Aero monas virulence.