Abstract

The presence of plasmid DNA in bacteria may provide information about the virulence of the bacterium since many plasmids can contain genes coding for toxins, antibiotic resistance factors or metabolites. In an attempt to characterize virulence factors in the pathogenic bacterium Erysipelothrix rhusiopathiae, a series of isolates implicated in the deaths of cetaceans were analyzed for the presence of plasmids. In previous studies, plasmids were detected in seven of forty-three isolates cultured from pigs suffering from chronic erysipelas.¹ Eleven isolates that were cultured from deceased or infected individuals of Delphinapterus leucas, Lagenorhynchus obliquidens, Tursiops truncatus and T. gilli were identified as E. rhusiopathiae by common microbiological and genetic procedures. These isolates, along with American Type Tissue Collection (ATTC) reference isolates of E. rhusiopathiae strains 1a and 2 (known to be pathogenic), were lysed using an alkaline lysis procedure and any plasmids present were purified with the Perfectprep® Plasmid Mini kit (Eppendorf). Escherichia coli strain AC156, known to contain plasmids, was used as a positive control. The plasmid preps were analyzed on a 1.0% agarose gel. At this time, plasmids have not been detected for any of the E. rhusiopathiae isolates. More plasmids preps will be done using alternate protocols to verify these results.

References

1.  Noguchi N, M Sasatsu, T Takahashi, K Ohmae, N Terakado, M Kono. 1993. Detection of plasmid DNA in Erysipelothrix rhusiopathiae isolated from pigs with chronic swine erysipelas. J Vet Med Sci 55:349-50.