Cloning and Transfer of the esp Gene from Enterococci to Salmonella

Fifteen Enterococcus faecium and 33 E. faecalis isolates were tested to determine the relationship between the presence of the esp gene and biofilm production. It was determined that 4 of the tested isolates contained esp gene. However, none of these strains containing the esp gene were significantly stronger biofilm producers than esp-negative strains. These data indicate that esp is not critical for biofilm formation both for Enterococcus faecium and E. faecalis. Cloning N-terminal domain of Esp protein and controlled expression under arabinose promoter experiments were performed. As a result of cloning and expression of esp, Salmonellatyphimurium LT2 became more adherent to polystyrene than wild type strain. These results demonstrate that: (i) Esp surface protein is not mandatory for biofilm production of E. faecium and E. faecalis strains, (ii) the presence of esp gene enhances biofilm formation of enterococci, (iii) horizontal transfer of esp gene may cause the spread of biofilm infections, not only among enterococcal strains but also different species such as Salmonella.