Synergy between circular bacteriocin AS-48 and ethambutol against Mycobacterium tuberculosis [PublishAheadOfPrint]

The increasing incidence of multi-drug resistant Mycobacterium tuberculosis and the very few drugs available for treatment is promoting the discovery and development of new molecules that could help in the control of this disease. Bacteriocin AS-48 is an antibacterial peptide produced by Enterococcus faecalis, active against several Gram-positive bacteria. We have found that AS-48 was active against Mycobacterium tuberculosis, including H37Rv and other reference and clinical strains, and also against some non-tuberculous clinical mycobacterial species. The combination of AS-48 with either lysozyme or with ethambutol (commonly used in the treatment of drug susceptible tuberculosis) increased the antituberculosis action of AS-48, showing a synergic interaction. Under these conditions, AS-48 exhibits a MIC close to some of the first-line antituberculosis agents. The inhibitory activity of AS-48 and its synergistic combination with ethambutol was also observed on M. tuberculosis infected macrophages.

Finally, AS-48 did not show any cytotoxicity against THP-1, MHS and J774.2 macrophage cell lines, at concentrations close to its MIC. In summary, bacteriocin AS-48 has an interesting antimycobacterial activity in vitro and low cytotoxicity, so further studies in vivo will contribute to its development as a potential additional drug for antituberculosis therapy.

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