Comparison of methods available for identification of Mycobacterium chimaera

International audienceObjectives: Mycobacterium chimaera is a recently described nontuberculous mycobacteriumbelonging to the M. avium complex (MAC). Because this species is implicated in a worldwideoutbreak due to contaminated heater-cooler unit water tanks during open-heart surgery, itbecomes mandatory for clinical microbiology laboratories to be able to differentiate M.chimaera from the other MAC species, especially M. intracellulare. Such identification wasso far restricted to specialized laboratories, since it required the analysis of several genesequences. The aim of this study was to evaluate commercialized methods for identifying M.chimaera with regard to the reference gene sequencing ITS, the internal transcribed spacer16-23S.Methods: 47 clinical and environmental isolates including 41 MAC were identified using (i)PCR sequencing of the ITS gene and of the hsp65 gene, (ii) three molecular biology kits(INNO-LiPA Mycobacteria, GenoType Mycobacterium CM and GenoType NTM-DR), and(iii) matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDITOFMS) using MicroFlex software.Results: There was a high concordance for species determination between the reference ITSsequencing and the GenoType NTM-DR test (39/41, 95%), the INNO-LiPA test (38/41, 93%)and the hsp65 sequencing (38/41, 93%). The GenoType CM test did not distinguish M.chimaera from M. intracellulare. MALDI-TOF MS distinguished two M. chimaera - M.intracellulare groups separated from M. avium and from the other mycobacterial species on ascore-oriented dendrogram, but did not differentiate the two species either.Conclusions: This study showed that INNO-LiPA and Genotype NTM-DR are efficientassays for M. chimaera identification in clinical microbiology laboratories