The effect of lantibiotic nisin on the inhibitory and bactericidal activities of antibiotics used against vancomycin resistant enterococci.

BACKGROUND: Antibiotic resistance is a real trouble facing clinicians all over the world. Vancomycin resistant enterococci (VRE) are amongst the most common resistant pathogens that are isolated with a significant rate from patients suffering from infection in our locality. New antimicrobial agents like the lantibiotic nisin have been previously examined against resistant bacteria as it has an immense antibacterial action with no chance of resistance development. OBJECTIVES: The present study was aiming at exploring the effect of nisin in combination with the conventional antibiotics against VRE, hoping that it could be used as an auxiliary therapy with such antibiotics for combating those resistant isolates. METHODS: Twenty-three VRE had been examined for the combined effect of nisin and the routine sets of antibiotics using the microplate dilution technique for Minimum Inhibitory Concentration (MIC) and Minimum Bactericidal Concentration (MBC) testing. Checkerboard microbroth assay was conducted for inspection of synergism between nisin and each of ampicillin and chloramphenicol. RESULTS: An obvious improvement of inhibitory and bactericidal activities of the tested antibiotics after addition of lantibiotic nisin had been observed, with remarkable reduction in the MIC values of vancomycin against all of the isolates. Nisin recorded synergistic outcome when combined with either ampicillin or chloramphenicol using the checkerboard assay. CONCLUSION: Nisin could be effectively considered as a supplementary agent with the traditionally used antibiotics in management of VRE associated infections, recording a synergistic outcome with the commonly prescribed antibiotics like ampicillin and chloramphenicol.