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Identification of Mycobacteroides abscessus complex subspecies and molecular determination of resistance to clarithromycin and amikacin

F Kontos(1) G Mavromanolakis(2) S Pournaras(1)

1:Laboratory of Clinical Microbiology, Attikon University Hospital, Medical School, National and Kapodistrian University of Athens, Athens, Greece; 2:Department of Internal Medicine. General Hospital of Agios Nikolaos, Crete, GreecePC 72100,

Objectives. Mycobacteroides abscessus complex (MABC) is a rapidly growing mycobacterium that encompasses three subspecies: M. abscessus subsp. abscessus (MAB), M. abscessus subsp. bolletii (MBO) and M. abscessus subsp. massiliense (MMA). This study aimed to investigate the diagnostic utility of a commercially available molecular assay that performed on MABC isolates recovered in a University Hospital from 1/2007 to 12/2023. 

Methods. We studied 47 MABC non-repetitive clinical isolates (29 MAB, 12 MBO and 6 MMA). For subspecies identification and molecular detection of mutations conferring resistance to clarithromycin and amikacin, we used the reverse-hybridization-based assay Genotype NTM-DR (BRUKER). The MICs of clarithromycin and amikacin, were determined with the standard broth microdilution method using the commercial assay Sensititreᵀᴹ RAPMYCOI, according to the CLSI recommendations and breakpoints. To investigate possible inducible clarithromycin resistance (CLA-IR), the incubation period was extended up to 14 days. Results of NTM-DR were compared with sequencing results of hsp65, erm(41), rrl, and  rrs  genes.   

Results. Four isolates were resistant to amikacin and clarithromycin harboring the A to G substitution at positions 1408 and 2508 of the rrs and rrl genes respectively.    All MMA isolates were susceptible to clarithromycin, having a 276-bp deletion in erm(41) gene. Thirty-three isolates were CLA-IR and five were susceptible having the T28 and C28 polymorphisms at erm(41) gene respectively. 

Conclusion. The NTM-DR assay is a useful tool for rapid (turn-around time of only 6 hours) and reliable identification of MABC subspecies and detection of resistance to amikacin and clarithromycin.

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