Uncommitted role of enterococcal surface protein, Esp, and origin of isolates on biofilm production by Enterococcus faecalis isolated from bovine mastitis.

PURPOSE This study was conducted in order to determine the occurrence of esp and biofilm formation among Enterococcus faecalis causing mastitis isolated from different bovine and environmental origins. MATERIALS AND METHODS A total of 41 E. faecalis isolates were obtained from clinical mastitis before antibiotic therapy, subclinical mastitis, dried manure bedding samples, and postpartum milk samples. Isolates were screened for biofilm formation using microtiter plate method using tryptic soy broth with 0.25% glucose as media. Isolates were tested for the presence of the esp gene, which has been reported to be essential for biofilm formation in enterococci, by means of the polymerase chain reaction. RESULTS Analysis of the relationship between the presence of esp and the biofilm formation capacity in E. faecalis showed that the esp gene was not identified in any of the 18 biofilm-producing E. faecalis isolates. Moreover, two of the three non-biofilm-producing E. faecalis strains were esp positive. In addition, the biofilm assay mean values were not changed with different origins of isolation. CONCLUSIONS These results suggest the following: (1) lack of strict association between the presence of esp and biofilm formation and (2) widespread biofilm formation capacity among different sources of E. faecalis isolates derived from bovine mastitis.