Direct identification of mycobacteria from BacTec MGIT 960 system tubes: comparative evaluation of INNO-LiPA Mycobacteria v2 and DNA AccuProbe assays
Abstract number: 1733_1481
Mokaddas E., Ahmad S.
Objective: Species-specific identification of mycobacteria is of clinical relevance since treatment varies according to the species causing infection. This study evaluated the performance of two commercial probe assays; INNO-LiPA MYCOBACTERIA v2 (LiPA) and AccuProbe for species-specific identification of mycobacterial isolates in Kuwait directly from MGIT 960 system tubes.
Methods: Seventy-three respiratory and extrapulmonary specimens flagged positive for growth by MGIT 960 system and smear-positive for mycobacteria were evaluated for identification. The AccuProbe assay was performed and interpreted according to the manufacturer's instructions. The DNA extraction, PCR amplification and hybridisation steps were performed by following the instructions supplied with the LiPA kit. The results were validated by PCR amplification and DNA sequencing of 16S-23S internal transcribed spacer (ITS) region.
Results: Each of the 73 tubes grew one mycobacterial culture. Both AccuProbe and LiPA identified 47 isolates as Mycobacterium tuberculosis complex (MTC) members and ITS region sequences of 8 randomly selected isolates were concordant. AccuProbe assay identified 26 isolates as non-tuberculous mycobacteria (NTM) with species-specific identification of 9 isolates. The ITS region sequences were concordant with the NTM status for 17 isolates and species-specific identification of 7 of 9 isolates while two M. intracellulare strains were actually M. chimaera and M. avium complex sequevar MAC-C isolates. The LiPA identified 21 isolates as NTM with species (or complex)-specific identification of 19 isolates while no result was obtained for 5 isolates (no amplicons with LiPA primers). The ITS region sequencing confirmed the species (or complex)-specific identification by LiPA of all the 19 isolates while 2 isolates detected only as NTM by LiPA were identified as M. immunogenum and M. lentiflavum. The DNA sequencing also identified 4 isolates yielding no result in LiPA as M. kansasii and one isolate as M. chimaera.
Conclusions: All the MTC isolates are correctly identified by both, the LiPA and AccuProbe assays. Although, AccuProbe assay identified only some (9 of 26) while LiPA identified most (19 of 26) NTM isolates to the species or complex level, the 4 M. kansasii isolates correctly identified by AccuProbe assay were not even detected by LiPA indicating variations in sequences targeted for LiPA amplification in M. kansasii strains in Kuwait.
Supported by KURA grant MI02/04.
|Session name:||European Society of Clinical Microbiology and Infectious Diseases|
|Location:||ICC, Munich, Germany|
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