Phenotypic and genotypic characterization of rapidly growing Non-tuberculous Mycobacteria (RGM) isolated from surgical site infection in Bangladesh

Rapidly growing mycobacteria (RGM) are a group of non-tuberculous mycobacteria capable of causing various human infections including surgical site infection. Although inherently resistant to the first-line anti-tubercular drugs, RGM are often misdiagnosed and mistreated as Mycobacterium tuberculosis. Additionally, their antimicrobial susceptibility and treatment modality varies depending on the species. The aim of this study was to identify the RGM at the species level, determine their sequence type and antibiotic susceptibility pattern with genes responsible for resistance.In this study, RGM was isolated from the pus and wound swab of surgical site infection. Species identification was done by phenotypic method and molecular technique i.e. Sanger sequencing, PCR using sub species-specific primers and PCR-Restriction enzyme analysis (PRA). Antibiotic susceptibility pattern was observed by broth micro dilution method. Sequence types and antimicrobial resistance genes were detected in 14 RGM isolates by Whole genome sequencing (WGS).Out of 51 RGM isolates, 37 (72.6%) were M. abscessus complex, 13 (25.5%) were M. fortuitum group and 01 (1.9%) were M. mageritense. Among all M. abscessus complex, 20 (54.1%) were M. abscessus subspecies massiliense and 17 (45.9%) were M. abscessus subspecies abscessus. Species were confirmed in 4 isolates of M. fortuitum group ie. M. fortuitum (01), M. conceptionense (02), M. farcinogens (01). M. abscessus complex were sensitive to only amikacin (100%), clarithromycin (78.4%) and linezolid (56.8%) where as M. fortuitum group were sensitive to meropenem (92.3%), ciprofloxacin (92.3%), moxifloxacin (100%), doxycycline (84.6) in addition to amikacin (100%), clarithromycin (84.6%) and linezolid (92.3%). M. mageritense was susceptible to ciprofloxacin, cotrimoxazole and meropenem only.Sequence types (ST) 5, 7, 33 and 63 were detected in selected RGM isolates. Seven drug-resistance genes aph(6)-Id, aac(3)-Ib, aac(2')-Ib , erm(41), erm(40), sul1 and tet(V) were detected and only 02 genes (erm40 and sul1) were seen to be phenotypically expressed.Majority of RGM isolates causing SSI were M. abscessus complex. Isolates identified as M. fortuitum group were less drug resistant than other RGM species. This inter-species variability of antibiotic susceptibility pattern necessitates RGM species identification and sensitivity testing prior to administration of antibiotics to avoid therapeutic failure.