This study was aimed at elucidating the role of virulence plasmid (pYV) in the susceptibility of Yersinia enterocolitica to bactericidal agents such as chlorine and heavy metals. Plasmid-bearing (pYV(+)) Y. enterocolitica was less susceptible to the antimicrobial action of chlorine and heavy metals compared with the isogenic plasmidless (pYV(-)) derivative. This difference was, however, observed only with bacteria cultured at 25 degreesC. pYV-associated susceptibility apart, cells cultured at 37 degreesC were also found to be less susceptible to the antimicrobial action of these agents. The results indicate that the susceptibility of Y. enterocolitica to these agents was influenced both by the presence of the virulence plasmid and the temperature at which the cells were cultured.