[Hybridization techniques and mycobacteria. Evaluation in hospital practice].

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.