Differential gene expression of three gene targets among persistent and non-persistent Listeria monocytogenes strains in the presence or absence of benzethonium chloride

Persistence of Listeria monocytogenes strains in food processing environments remains relatively common but is difficult to control. Understanding the basis for such persistence represents an important step in the potential control or eradication of this pathogen from these environments. In this study, reverse transcription PCR was used to determine the relative and absolute expression of selected gene targets (pocR, eutJ, and qacH) among five persistent and four presumed nonpersistent L. monocytogenes strains. The quantification of these genes as markers for the persistent phenotype and the effect of benzethonium chloride (BZT) on their expression was investigated. Although no markers correlated with the ability of strains to persist in food processing facilities were found, expression of pocR was upregulated in three of the five persistent strains, in contrast to the four presumed nonpersistent strains, which showed down-regulation of this gene. These results provide further knowledge of the differential expression of genes of persistent and presumed nonpersistent strains of L. monocytogenes grown in the presence or absence of BZT and identifies upregulation of pocR as a potential response of persistent strains of L. monocytogenes to exposure to BZT.