A review of tigecycline resistance in nontuberculous mycobacteria.

The genus Mycobacterium comprises nontuberculous mycobacteria (NTM), which are opportunistic environmental pathogens primarily associated with chronic lung disease. Among current therapeutic options, tigecycline has emerged as a promising alternative for treating NTM due to its broad spectrum of activity, including efficacy against certain mycobacterial species. In this review, we compiled 28 studies investigating the mechanisms and prevalence of tigecycline resistance in NTM. The evidence suggests that tigecycline is less impacted by the monooxygenase MabTetX, the principal tetracycline resistance determinant in M. abscessus. However, adaptive mechanisms, such as WhiB7 regulation, alterations in the sigH-rshA axis, and overexpression of efflux pumps (MmpL), can increase the minimum inhibitory concentration (MIC). In contrast, slow-growing NTM species, including M. avium and M. kansasii, exhibit low intrinsic susceptibility, reflected by high MIC values. We conclude that tigecycline is a promising component of combination of regimens for rapid-growing NTM, although its efficacy against slow-growing species remains limited and standardized breakpoints have not yet been established. .