Objetive:

To determine the S315T mutation of the katG gene in Mycobacterium tuberculosis isoniazid-resistant isolates by PCR-RFLP.

Materials and Methods:

Polymorphism analysis of 1054 and 630 bp products containing the S315T mutation of the katG gene was performed by PCR-RFLP using the MspI and SatI restriction enzymes from 68 Mycobacterium tuberculosis isolates. Sensitivity, specificity, positive and negative predictive values, positive and negative likelihood ratio were determined using SPSS.

Results:

74.46% of isoniazid-resistant and 4.76% of isoniazid-sensitive isolates showed the S315T mutation in katG gene. The PCR-RFLP for S315T of the katG gene had 85.4% sensitivity and 95.2% specificity with MspI and 85.4% sensitivity and 94.4% specificity with SatI.

Discussion:

The PCR-RFLP has a high resolutive capacity that depends on the enzyme that is used as it was observed in previous studies. The presence of the S315T mutation in treatment-naive patients suggests the circulation of isolates resistant to isoniazid.

Conclusion:

PCR-RFLP is a valid and rapid alternative for the diagnosis of isoniazid resistance, by detection of S315T mutation in the katG gene compared to the conventional method of proportions.

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