[Hybridization techniques and mycobacteria. Evaluation in hospital practice]

Abstract

Background: Commercially DNA probes procedure for identification of M. tuberculosis complex and M. avium complex isolates were evaluated, for accuracy and applicability, for use in the clinical laboratory.

Methods: Gen-Probe culture confirmation tests for M. tuberculosis complex and M. avium complex were performed on 94 mycobacterial isolates.

Results: Results were expressed as absolute percent hybridization, with values greater than or equal to 10% considered positive. The M. tuberculosis complex probes correctly identified 71 of 75 isolates, with 4 false-negative, for a sensitivity of 94.6% and a specificity of 100%. After repeat testing, all isolates were correctly identified, for a sensitivity of 100% and specificity of 100%. The M. avium complex probes correctly identified all M. avium-intracellulare isolates. There were no false-positives with 16 other mycobacteria. The mean percent hybridization (+/- the standard deviation) of M. tuberculosis complex isolates was 33.5 +/- 10.6; and for M. avium complex was 49.1 +/- 2.3. Among the isolates non M. tuberculosis and non M. avium complex, the percent hybridization range was 0.9 to 4.6. Overall, there were 4 discrepant M. tuberculosis results after repeat testing, being necessary to repeat it if the percent hybridization is between 10 and 5.

Conclusions: GenProbe kits are highly sensitive and specific for use in identifying M. tuberculosis complex and M. avium complex isolates and will be useful in the clinical laboratory with a representative number of isolates.