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A significant proportion of MAG isolates demonstrate inducible resistance to clarithromycin that is only detectable with an extended 14 day incubation. Further, the majority of clarithromycin-susceptible MAG isolates have characteristic deletions in erm(41) that can rapidly and reliably be detected by a simple PCR.

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The present study showed 100% concordance between both readings, with REMA providing easier to read and report results benefit. This change in reading can also reflect on the MIC determination and report, improving the test.

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Introduction. The M. abscessus molecular identification and its drug-resistance profile are important to choose the correct therapy. Aim. This work developed a multiplex real-time PCR (mqPCR) for detection of clarithromycin resistance genes for the Mycobacterium abscessus group. Methodology. Isolates received by Adolfo Lutz Institute from 2010 to 2012, identified by PCR restriction enzyme analysis of a fragment of the hsp65 gene (PRA-hsp65) as M. abscessus type 1 (n=135) and 2 (n=71) were used. Drug susceptibility test (DST) for CLA were performed with reading on days 3 and 14. Subespecies identification by hsp65 and rpoB genes sequencing and erm(41) and rrl genes for mutation detection and primer design were performed. erm(41) gene deletion was detected by conventional PCR. Primers and probes were designed for five detections: erm(41) gene full size and with deletion; erm(41) gene T28 and C28; rrl gene A2058. Results. In total, 191/206 (92.7 %) isolates were concordant by all methods and 13/206 (6.3 %) were concordant only between molecular methods. Two isolates (1.0 %) were discordant by mqPCR compared to rrl gene sequencing. The mqPCR obtained 204/206 (99.0 %) isolates in agreement with the gold standard, with sensitivity and specificity of 98 and 100 %, respectively, considering the gold standard method and 92 and 93 % regarding DST. Conclusion. The mqPCR developed by us proved to be an easy-to-apply tool, minimizing time, errors and contamination.