Virulence factors in clinical and commensal isolates of Enterococcus species

BACKGROUND: Enterococci have emerged as important nosocomial pathogens and have been found to possess many virulence factors, some of which are considered very important in the pathogenesis of diseases caused by them. The following study was carried out to evaluate some of the virulence determinants elaborated by strains of enterococci in our setup and to ascertain if these strains differ considerably from commensal strains of enterococci in the expression of these virulence determinants. MATERIALS AND METHODS: One hundred and fifty-seven isolates of Enterococcus species from clinical specimens were evaluated for the presence of virulence determinants like hemolysin production, gelatinase production and biofilm formation by phenotypic tests. The presence of enterococcal surface protein (esp) gene in the isolates was detected using polymerase chain reaction (PCR). Thirty strains of Enterococcus isolated from fecal samples of patients admitted to the hospital were also tested for the presence of these virulence factors. Strains of Enterococcus from clinical specimens and those present as commensals were compared with respect to the elaboration of virulence factors using Fisher's exact test. RESULTS: The association between biofilm formation and presence of the "esp" gene was not found to be statistically significant. Among the virulence determinants studied, gelatinase production and the "esp" gene were found to be significantly more common in clinical isolates than commensal strains of Enterococcus species. CONCLUSION: Among the virulence factors, gelatinase and the "esp" gene were more common in clinical isolates than commensal strains. The association between biofilm formation and the presence of "esp" gene was not found to be statistically significant.