Susceptibility Patterns in Clinical Isolates of Complex from a Hospital in Southern Spain.

The incidence of infections caused by the complex (MAC) has risen significantly, posing diagnostic and therapeutic challenges. This study analyzed 134 clinical isolates of the complex from southern Spain, performing in vitro antimicrobial susceptibility testing using a commercial microdilution technique to generate additional data, refine treatment strategies, and improve patient outcomes. Phenotypic susceptibility testing revealed clarithromycin and amikacin as the most effective antibiotics, with susceptibility rates exceeding 90%, while linezolid and moxifloxacin exhibited limited activity, with resistance rates of 49.3% and 41.8%. A comparative analysis between and showed significant differences in resistance to amikacin and linezolid, with exhibiting higher resistance rates. Additionally, species-specific differences were observed in MIC distributions for ethionamide, ciprofloxacin, and streptomycin. Our data reveal regional variability in resistance patterns, particularly for moxifloxacin and linezolid, which exhibit differing resistance rates compared to studies from other regions. The significant MIC differences for several antibiotics between and underscore the importance of species-level identification and the heterogeneity in resistance mechanisms within MAC.