Whole-genome and pangenome insights into Mycobacterium colombiense clinical isolates from human infections

Background: Nontuberculous mycobacteria are opportunistic pathogens which cause infections in various tissues, with the Mycobacterium avium complex (MAC) being a major cause of pulmonary diseases. Among MAC members, Mycobacterium colombiense is a clinically significant species with recognized pathogenic potential; however, studies on its genomic structure and genetic diversity remain limited. Methods: This study investigated the drug susceptibility profiles and performed whole-genome sequencing of 12 clinical M. colombiense isolates from the Clinical Microbiology Laboratory at Srinagarind Hospital, Khon Kaen University, Khon Kaen, Thailand. Results: Based on minimum inhibitory concentration values, moxifloxacin resistance was most prevalent (100%), followed by linezolid (90%), clarithromycin (30%), and amikacin (30%). The presence of antibiotic resistance genes and virulence factors, including ESX secretion systems and efflux pumps, highlights the bacterium’s potential for immune evasion and survival under stress. Single nucleotide polymorphism-based phylogenetic analysis revealed a close genetic relatedness between the isolates. Pangenome analysis of 16 M. colombiense genomes (12 newly sequenced and four publicly available) identified 7,771 gene clusters, comprising 4,468 core genes, 1,834 accessory genes, and 1,469 unique genes, supporting a closed pangenome structure and indicating evolutionary conservation and low genetic variability among isolates. Conclusions: This study provides valuable insight into the genomic diversity, antimicrobial resistance profiles, and virulence potential of M. colombiense isolates. These findings enhance understanding of the pathogen and may inform clinical management, targeted diagnostic development, and therapeutic strategies.