Antibiotic Susceptibility Profile of Mycobacterium intracellulare Clinical Strains Isolated From Southwestern Gyeongnam Province in South Korea Using the Resazurin‐Based Microtiter Assay

Mycobacterium avium complex (MAC) infection is a growing public health concern worldwide, particularly affecting the elderly and immunocompromised population. The treatment of MAC lung disease relies on a combination of antibiotics in a three-drug regimen that includes macrolides, rifamycins, and ethambutol. Therefore, the investigation of antimicrobial susceptibility is crucial for successful treatment. This study aimed to assess the antibiotic susceptibility of the most prevalent MAC species causing MAC lung disease, Mycobacterium intracellulare, in the Southwestern Gyeongsang province of South Korea using a resazurin-based microtiter assay. A total of 97 strains of M. intracellulare were isolated and tested for antimicrobial susceptibility. The results demonstrated high susceptibility rates for two aminoglycosides (amikacin and streptomycin, 94.9% and 99%), rifampicin (90.9%), clarithromycin (98%), linezolid (100%), and moxifloxacin (94.9%) against M. intracellulare. However, notably high resistance rates were observed for ethambutol (97%) and clofazimine (98%) against M. intracellulare. In conclusion, our findings indicate relatively high susceptibility rates for these six antibiotics and significantly elevated resistance rates for clofazimine and ethambutol compared to other regions in South Korea and foreign countries. The investigated MIC data can offer valuable insights for developing an effective treatment regimen for MAC lung infection in this area.