Enterocins Produced by Enterococci Isolated from Breast-Fed Infants: Antilisterial Potential

Enterocins are bacteriocins synthesized by strains that show an interesting antimicrobial effectiveness against foodborne pathogens such as . The objectives of this study were to identify and analyze the expression of enterocin genes of isolated from breast-fed infants and evaluate their ability to inhibit three human isolates of virulent , as well as some probiotic bacteria. The susceptibility of the strains of to fifteen antibiotics was tested, detecting their resistance to cefoxitin (constitutively resistant), oxacillin, and clindamycin. The production of enterocins A, B, and P was observed in isolates, while enterocin AS-48 was detected in an isolate. AS-48 showed antilisterial activity by itself, while the joint action of enterocins A and B or B and P was necessary for inhibiting , demonstrating the synergistic effect of those combinations. The presence of multiple enterocin genes does not assure the inhibition of strains. However, the expression of multiple enterocin genes showed a good correlation with the inhibition capacity of these strains. Furthermore, the potential beneficial strains of lactobacilli and bifidobacteria examined were not inhibited by any of the enterocins produced individually or in combination, with the exception of BB536, which was inhibited by enterocin AS-48 and the joint production of enterocins A and B or B and P. The enterocins studied here could be candidates for developing alternative treatments against antibiotic-resistant bacterial infections. Moreover, these selected enterocin-producing strains isolated from breast-fed infants could be used as probiotic strains due to their antilisterial effect, as well as the absence of virulence factors.