The basis of drug resistance in Mycobacterium abscessus is still poorly understood.\nNevertheless, as seen in other microorganisms, the efflux of antimicrobials may also play a role\nin M. abscessus drug resistance. Here, we investigated the role of effluxpumps in clarithromycin\nresistance using nine clinical isolates of M. abscessus complex belonging to the T28 erm(41) sequevar\nresponsible for the inducible resistance to clarithromycin. The strains were characterized by drug\nsusceptibility testing in the presence/absence of the effluxinhibitor verapamil and by genetic analysis\nof drug-resistance-associated genes. Effluxactivity was quantified by real-time fluorometry. Efflux\npump gene expression was studied by RT-qPCR upon exposure to clarithromycin. Verapamil\nincreased the susceptibility to clarithromycin from����������
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