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Journal of Clinical Microbiology, 11 1997, 2767-2772, Vol 35, No. 11
A Devallois, M Picardeau, CN Paramasivan, V Vincent and N Rastogi
Based on cultural and biochemical tests, a total of 84 strains (72 clinical
and 12 environmental isolates from the Caribbean Isles, Europe, and the
Indian subcontinent) were identified as members of the Mycobacterium avium
complex (MAC). They were further characterized with MAC, M. avium, and M.
intracellulare probes of the AccuProbe system, and this was followed by
selective amplification of DT6 and DT1 sequences. Seventy isolates gave
concordant results; 63 were identified as M. avium, 5 were identified as M.
intracellulare, and 24 remained untypeable by both methods. Fourteen
isolates gave discrepant results, as they were DT1 positive but gave
negative results by the M. intracellulare AccuProbe test. Consequently, a
detailed molecular analysis of all DT1-positive isolates (14 discrepant
strains plus 5 M. intracellulare strains) was performed by PCR-restriction
analysis (PRA) of the hsp65 gene and 16S rRNA gene sequencing. The results
confirmed the reported heterogeneity of M. intracellulare, as only 6 of 19
isolates (32%) gave PRA results compatible with published M. intracellulare
profiles while the rest of the isolates were grouped in four previously
unpublished profiles. 16S rRNA gene sequencing showed that only 8 of 19
isolates (42%) were related to M. intracellulare IWGMT 90247 (EMBL
accession no. X88917), the rest being related to MCRO19 (EMBL accession no.
X93030) and MIWGTMR10 (EMBL accession no. X88915). In conclusion, we have
characterized a significant number of MAC isolates which were not
identified by the AccuProbe test, PRA, or 16S rRNA sequencing. However, all
of them were identifiable by DT1-DT6 PCR (they were DT6 negative and DT1
positive) and could be tentatively identified as M. intracellulare based on
previously published observations. It is noteworthy that the majority of
such isolates (14 of 19) were from the Indian subcontinent, with 12 of 14
being environmental isolates. Our study confirms the marked heterogeneity
of M. intracellulare isolates and shows the utility of in-house DT1 PCR to
detect this group of isolates, which would otherwise have been missed by
the AccuProbe system in a routine clinical microbiology laboratory.
Copyright © 1997 by the American Society for Microbiology. All rights reserved.
Molecular characterization of Mycobacterium avium complex isolates giving discordant results in AccuProbe tests by PCR-restriction enzyme analysis, 16S rRNA gene sequencing, and DT1-DT6 PCR [In Process Citation]
Unite de la Tuberculose et des Mycobacteries, Institut Pasteur, Pointe- a-Pitre, Guadeloupe, French West Indies.
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