Study on antibacterial effect of fusidic acid combined with antibiotics against Mycobacterium abscessus

Abstract:

In order to explore the new antibacterial strategy against Mycobacterium abscessus, this study used the microplate alamar blue assay (MABA) method to determine the minimum inhibitory concentrations (MICs) of fusidic acid and other drugs on the standard strains and clinical isolates. The checkerboard method was used to determine the antibacterial effect of fusidic acid combined with drugs, while the minimum bactericidal concentrations (MBCs) were determined by the plate coating method. The results showed that the MIC90 of fusidic acid, azithromycin, ceftriaxone sodium, bedaquiline alone against the standard strain of M.ab was 50 μg/mL, 6.25 μg/mL, 3.13 μg/mL, and 3.13 μg/mL, respectively. And the MBCs of those alone against the standard strain of M.ab were 50, 12.5, 3.13, 6.25 μg/mL, respectively. The fractional inhibitory concentration index (FICIs) of fusidic acid combined with azithromycin ranged from 0.09~2.0. Fusidic acid has good antibacterial activity against M. ab in vitro, and the combination of fusidic acid with azithromycin showed an obvious synergistic effect in vitro bacteriostatic effect on both standard and clinical strains of M.ab, which significantly reduced the MICs and MBCs of the drug, and the combination with ceftriaxone sodium showed synergistic on standard strains and additive effect on clinical strains. After combined with bedaquiline, it showed additive effects on standard strains while irrelevant effects on clinical strains.

Key words:Mycobacterium abscessus; Fusidic acid; Azithromycin; Minimum inhibitory/bactericidal concentrations; Synergistic effect