New bacteriocin of E. Faecalis CECT7121: synergy studies against multidrug-resistant enterococci isolated from bovine mastitis

Abstract

Bovine mastitis impacts negatively on animal production and on the quality of milk. AP-CECT7121, a new bacteriocin produced by Enterococcus faecalis CECT7121, shows a variety of interesting biological properties with potential use in clinical Veterinary practice, without undesirable side effects. It is a peptide with a wide spectrum of bactericidal activity against Gram positive bacteria and bacteriostatic activity against some Gram negative bacteria. The aim of this study was to evaluate the synergism of AP-CECT7121 associated with gentamicin against multidrug-resistant enterococci isolated from bovine mastitis. N: 4 multidrug-resistant E. faecium strains isolated from different mastitic dairy cows were tested. Animals from dairy farms, located in the Province of Buenos Aires-Argentina, during the period 2014-2015 were included. AP-CECT7121 potency was assessed by time-kill curves alone or with sub-inhibitory concentrations of gentamicin. High level gentamicin resistance was not observed in any enterococcal isolate. Viable counts, after 0, 2, 4, 8 and 24 h of incubation, were carried out. The AP-CECT7121exhibited bactericidal activity alone against all tested enterococci. The association with gentamicin slightly enhanced bactericidal activity against all isolates of E .faecium. Bactericidal activity of AP-CECT7121 alone and associated with subinhibitory concentrations of gentamicin against enterococci proved that this peptide constitute an attractive candidate for its use as a natural therapeutic tool for control and prevention of bovine mastitis produced by multi-resistant bacteria such as vancomycin-resistant E. faecium.