Synergistic effect of haloduracin and chloramphenicol against clinically important Gram-positive bacteria

Abstract

The emergence of drug-resistant pathogens has triggered the search for more efficient antimicrobial agents and formulations for treatment of infections. In recent years, combination therapy has become one of the effective clinical practices in treating infections. The present study deals with the effect of haloduracin, a lantibiotic bateriocin and chloramphenicol against clinically important bacteria. The combined use of haloduracin and chloramphenicol resulted in remarkable synergy against a spectrum of microorganisms including strains of Staphylococcus aureus, Enterococcus faecium, Enterococcus faecalis and different groups of Streptococcus. The synergy allowed using these antimicrobial agents at substantially reduced concentrations without compromising their efficiency. Use of lower doses of chloramphenicol can avoid the severity of its side effects. In addition to minimizing undesirable side effects of some drugs, this approach brings the possibility of using antibiotics that are no longer effective due to drug resistance. Furthermore, the observed synergy between haloduracin and chloramphenicol opens a new window of using bacteriocins and antibiotics in combination therapy of infections.

Keywords: Chloramphenicol; Combination therapy; Drug resistance; Haloduracin; Topical antibiotics.

Fig. 1

The effect of haloduracin and antibiotics against B. subtilis. (a) The combined use of lantibiotic (5.4 μg/ml) and Ampicillin (20 μg/ml) which did not show any synergistic effect. (b) The combined use of lantibiotic (5.4 μg/ml) and chloramphenicol (4 μg/ml) which acted synergistically. Culture of B. subtilis (ATCC168) in only tryptic soy broth (●, dashed line), and in presence of haloduracin (▲, dashed line), in presence of ampicillin (◊) or chloramphenicol (◊) and in presence of both haloduracin and antibiotic (■).

Fig. 2

The effect of haloduracin and different concentrations of chloramphenicol against B. subtilis (ATCC168). Culture turbidity of B. subtilis after 24 h of cultivation in presence of different concentration of chloramphenicol (▲) or in combined presence of haloduracin (5.4 μg/ml) and different concentration of chloramphenicol (■).