Abstract:

Objective: To evaluate the in vitro inhibitory activity of fusidic acid (FA) against mycobacteria. Methods: The standard strains and clinical isolates of mycobacteria stored in the strain bank of Beijing Chest Hospital, Capital Medical University were selected as the research strains. There were 45 standard strains of mycobacteria, including 26 rapidly growing mycobacteria (RGM) strains and 19 slowly growing mycobacteria (SGM) strains. A total of 129 clinical isolates of mycobacteria were isolated from Beijing Chest Hospital, Capital Medical University from January 2017 to December 2018, including 26 Mycobacterium tuberculosis (MTB) sensitive strains, 29 multidrug-resistant (MDR) strains, 30 extensive drug-resistant (XDR) strains, 23 Mycobacterium avium strains and 21 Mycobacterium gordon strains. Broth microdilution method was used to test the minimal inhibitory concentrations (MIC), MIC₅₀, MIC₉₀ and MIC₉₉ of mycobacteria strains against FA, and the strains with MIC ≤16μg/ml were defined as FA sensitive strains. The drug resistance of the strains to FA was analyzed. Results: The resistance rates of RGM and SGM standard strains to FA were 23.1% (6/26) and 21.1% (4/19), respectively. The MIC₅₀, MIC₉₀, and MIC₉₉ values of FA for MDR-MTB clinical isolates were 4, 16, and 16μg/ml, respectively. The resistance rate of MTB clinical isolates to FA was 3.5% (3/85), with the resistance rates of MTB drug sensitive strains, MDR-MTB, and XDR-MTB strains being 0, 0, and 10.0% (3/30), respectively. The resistance rates of clinical isolates of Mycobacterium avium and Mycobacterium gordon to FA were 17.4% (4/23) and 9.5% (2/21), respectively. The MIC₅₀, MIC₉₀, and MIC₉₉ values of FA for clinical isolates of mycobacterium were 4, 16, and >32μg/ml, respectively. The overall resistance rate of FA for clinical isolates of mycobacterium was 7.0% (9/129). Conclusion: FA has high antibacterial activity against mycobacterium species and has a good antibacterial effect on MTB clinical isolates.

Key words: Mycobacterium, Microbial sensitivity tests, Anti-bacterial agents, In vitro, Fusidic acid