Differences in biofilm formation and virulence factors between clinical and fecal enterococcal isolates of human and animal origin.

The present study investigated the possible correlation between carriage of the virulence genes esp and fsrb, production of hemolysin and gelatinase and biofilm formation in human vs. animal enterococcal isolates. A collection of 219 enterococcal isolates recovered from clinical and fecal surveillance samples of hospitalized patients and 132 isolates from animal feces were studied. Isolates were tested for hemolysin and gelatinase phenotypically and for quantitative biofilm production by a microtitre method. Genes esp and fsrb were detected by PCR. Human Enterococcus faecium and Enterococcus faecalis isolates from both surveillance and clinical samples produced biofilm significantly more often than animal isolates (P < 0.0001 for both species). The quantity of biofilm did not differ significantly between human and animal isolates, while was significantly higher in esp-positive compared with esp-negative human E. faecium isolates (P < 0.0001). The frequency of esp gene carriage was significantly higher in human compared with animal E. faecium and E. faecalis isolates (P < 0.0001). The gene fsrb was detected significantly more often in animal than human E. faecium isolates (P 0.004). Hemolysin production was significantly more common in human clinical compared with animal E. faecalis isolates (P < 0.0001). Similar proportions of animal and human E. faecalis produced gelatinase, which was significantly correlated with the presence of fsrb gene (P < 0.0001) in both human clinical and animal E. faecalis isolates. The hemolysin trait did not exhibit any correlation with the presence of esp and fsrb genes, but appeared to be linked with enhanced quantity of biofilm production in both human clinical and animal E. faecalis isolates. Production of gelatinase was associated with the proportion and the degree of biofilm production mainly in animal E. faecalis isolates.