Abstract:

Objective: To analyze the antibacterial effects of 17 antibiotics on clinical isolates of rapidly growing mycobacteria (RGM) in Beijing, and to provide a reliable theoretical basis for the clinical treatment of nontuberculosis mycobacteriosis caused by RGM. Methods: A total of 130 nontuberculous mycobacteria (NTM) strains isolated from the Tuberculosis Laboratory of the Beijing Center for Disease Control and Prevention between January 2016 and December 2020 were collected for strain identification. After reviving the RGM clinical isolates and corresponding standard strains, sensitivity tests were conducted on 17 antibiotics (amikacin, ciprofloxacin, compound sulfamethoxazole, clarithromycin, linezolid, moxifloxacin, doxycycline, minocycline, cefoxitin, tigecycline, tobramycin, imipenem, meropenem, amoxicillin/clavulanic acid, bedaquiline, delamanid, and clofazimine) using the micro broth dilution method. The minimum inhibitory concentration (MIC) and the MIC values required to inhibit 50% (MIC₅₀) or 90% (MIC₉₀) of the tested bacteria were recorded. Results: After strain identification and successful recovery, 37 strains of RGM were identified, including 19 Mycobacterium (M.) abscesses, 17 M.fortuitum, and 1 M.chelonae. Among the 14 antibiotics with established resistance breakpoints, all RGM clinical isolates were found to be sensitive to tigecycline. Clinical isolates of M.chelonae and M.abscessus were sensitive to clarithromycin, and M.abscesses were also sensitive to linezolid. All M.fortuitum clinical isolates were sensitive to amikacin, ciprofloxacin, compound sulfamethoxazole, and moxifloxacin. Additionally, the sensitivity rate of M.abscessus to amikacin was 73.7% (14/19), while the sensitivity rates of M.fortuitum to linezolid and meropenem were 82.4% (14/17) and 88.2% (15/17), respectively. All M.abscessus isolates were resistant to doxycycline, amoxicillin/clavulanic acid, while all M.fortuitum isolates were resistant to tobramycin. Additionally, the MIC₉₀ of bedaquiline and clofazimine for RGM clinical isolates were both lower than the minimum detection limit of the drug sensitivity plate, whereas the MIC₉₀ of delamanid was higher than the maximum detection limit of the drug sensitivity plate. Conclusion: Tigecycline, amikacin, linezolid, betaquiline, and clofazimine all exhibit good in vitro antibacterial activity against RGM, while doxycycline, amoxicillin/clavulanic acid, and delamanid show almost no in vitro antibacterial activity. There is a significant difference in the drug resistance spectrum between NTM species. Therefore, it is recommended to conduct species identification and drug sensitivity testing before treatment to select appropriate antibiotics.

Key words: Mycobacteria,atypical, Rapidly growing mycobacteria, Microbial sensitivity tests, Evaluation studies