Genetic diversity and clinical spectrum of Mycobacterium abscessus complex in India

The Mycobacterium abscessus complex is a rapidly growing nontuberculous mycobacterium that causes chronic lung, skin, and soft-tissue infections. Disease management is challenging because of prolonged antibiotic therapy and resistance, making knowledge of local strain diversity and resistance patterns essential. However, the molecular epidemiology of M. abscessus in India remains largely unreported.

Whole-genome sequencing and multilocus sequence typing (MLST) were performed on 50 clinical isolates collected from patients across 10 Indian states (2019-2024). Genomic DNA was extracted, and sequencing was performed using the Illumina platform. MLST was conducted according to the PubMLST scheme based on seven housekeeping genes.

Analysis of the 50 isolates from 10 states across India showed a predominance of M. abscessus subsp. abscessus (76%), with extrapulmonary infections, particularly skin and soft-tissue infections. No isolates of subsp. bolletii were detected. MLST revealed genetic heterogeneity. M. abscessus subsp. abscessus isolates were distributed across 8 known and 18 novel sequence types (STs), with ST-5 being the most common, while M. abscessus subsp. massiliense isolates were predominantly assigned to ST-46, ST-33, and ST-37, along with two novel STs. Overall, 40% of the isolates represented novel STs.

This study revealed extensive genomic diversity, with 40% of the isolates representing novel STs. The predominance of subsp. abscessus and the high frequency of extrapulmonary infections highlight region-specific trends and underscore the need for strengthened genomic surveillance.