Transcriptional analysis of virulence-related genes in enterococci from distinct origins

Aims: The role of enterococci in food fermentation and as probiotics counteracts with their increasing importance as human pathogens. Over the years, several virulence factors have been described, mainly in clinical strains but also in food isolates. However, differential expression of such traits may modulate the pathogenic potential of the harbouring enterococci. To further unravel such differential response, this study aims to identify environmental cues responsible for triggering the expression of virulence-related genes. Methods and Results: The differential expression of eight virulence-related genes (cylMBAI, agg, esp, efaA(fs) and efaAfm) in 16 enterococci from distinct origins, grown in conditions simulating environmental colonization and infection sites, was analysed by reverse transcriptase PCR. The expression profiles were environmental and strain-dependent, because no constant response was observed neither for clinical nor food enterococci. Conclusions: Virulence expression profiles are strain-specific and unrelated with strain's origin or species allocation. Significance and Impact of the Study: The current study constitutes the first approach aimed at the evaluation of the differential expression of enterococcal virulence-related genes combining so many growth environments, enterococcal species and origins. So, with this investigation, we intend to contribute to the clarification of enterococcal pathogenicity potential, especially for food strains.