Pattern of InhA and KatG mutations in isoniazid monoresistant Mycobacterium tuberculosis isolates

The aim of the study is to detect the pattern of genetic mutation, i.e., Inh A or Kat G or both (Inh A and kat G) in isoniazid (INH) monoresistant mycobacteria and to correlate with the pattern in multidrug-resistant (MDR) isolates.

In this study, a quantitative research approach was used. The research design was descriptive observational study. The study was conducted at the Department of Respiratory Medicine, JLN Medical College, Ajmer, Rajasthan, and Intermediate Referral Laboratory, State TB Demonstration Centre, Ajmer. A total of 298 samples found to have resistant strains of Mycobacterium tuberculosis were enrolled with purposive sampling.

The mean age of patients was 40.27 ± 13.82 years. There were 250 (83.9%) males, while 48 (16.1%) were females. One hundred ninety-two (64.4%) were resistant for INH only, while the rest were resistant to both INH as well as rifampicin (MDR-tuberculosis). The most common mutation in INH monoresistance was kat G (125; 65.1%) as compared to inh A (54; 28.1%) and both inh A and kat G (13; 6.7%). Among kat G mutations, the most common gene pattern was the absence of WT (S315T) and the presence of MUT1 (S315T1).

Knowledge about mutation patterns of different INH resistant strains is important in the present era where there is a provision of separate regimens for INH monoresistant TB. Since these mutations are very closely related to high- or low-degree resistance to INH, the therapeutic regimens cannot be generalized.