In Vitro Susceptibility Testing of Imipenem-relebactam and Tedizolid Against 102 Mycobacterium Abscessus Isolates

Objectives: Mycobacterium abscessus is an emerging infection in people living with lung diseases, including cystic fibrosis (CF) and bronchiectasis, and it has limited treatment options and low cure rates. The off-label use of novel antibiotics developed for other bacterial pathogens offers potential new therapeutic options. We aimed to describe the in vitro activity of imipenem, imipenem-relebactam and tedizolid against comparator antibiotics in M. abscessus isolates from Australian patients with and without CF.

Methods: We performed susceptibility testing for imipenem-relebactam, tedizolid and comparator antibiotics by Clinical and Laboratory Standards Institute (CLSI) criteria against 102 clinical M. abscessus isolates, including 46 from people with CF.

Results: In this study, the minimum inhibitory concentration (MICs) of imipenem-relebactam was one-fold dilution less than of imipenem alone. The MIC and MIC of imipenem-relebactam were 8 and 16 mg/L, respectively, whereas for imipenem they were 16 and 32 mg/L. Tedizolid had an MIC and MIC of 2 and 4 mg/L, respectively. Forty non-CF isolates had linezolid susceptibility performed, with MIC and MIC values of 16 and 32 mg/L, respectively, measured.

Conclusions: This study shows lower MICs for imipenem-relebactam and tedizolid compared to other more commonly used antibiotics and supports their consideration in clinical trials for M. abscessus treatment.