Comparison of genus- and species-specific probes for PCR detection of mycobacterial infections.

We describe experiments comparing use of different DNA probes to detect mycobacteria in clinical specimens after PCR. The objective was to assess correlation between results using Mycobacterium genus-specific, and species-specific M. tuberculosis probes. Given sufficient concordance, sequential use of such probes would provide a useful screening tool. An evaluation of genus-specific probes compared use of repetitive sequences in the clone pMAv17 with the 65-kDa sequences. Sensitivity was 100% for pMAv17, 93% using the 65-kDa sequence; specificity was 70% for both. We then compared M. tuberculosis-specific probes developed by us (Tb400) with IS6110 and mpt40. Sensitivity using Tb400 was 100%; using IS6110 was 97%, and using mpt40 was 50%. Specificity using Tb400 and IS6110 was 68%, and was 70% using mpt40. Fourteen specimens which were PCR-positive and culture-negative, were positive using both genus probes, and the M. tuberculosis-specific probes Tb400, and IS6110. Ten of these were positive using mpt40.