Conventional and molecular determination of drug resistance in Mycobacterium tuberculosis and Mycobacterium bovis isolates in cattle

This study was aimed out to explore the presence of drug resistance among M. tuberculosis and M. bovis isolates (n = 51) of bovine origin by conventional broth microdilution method and molecular methods. By broth microdilution method, 16 isolates were found to be resistant to isoniazid, 08 isolates were resistant to pyrazinamide, 09 isolates were resistant to rifampicin and 07 isolates were found to be resistant for ethambutol. Two isolates showed resistance to rifampicin and pyrazinamide, one isolate showed resistance to pyrazinamide and ethambutol and 03 isolates showed resistance to isoniazid and ethambutol. None of isolates showed multi drug resistance (MDR). Other than the M. bovis strains, none of the other M. tuberculosis isolates showed any resistance to pyrazinamide. Molecular methods by multiplex PCR targeting katG, pncA, rpoB genes, multiplex allele specific PCR to detect mutation in embB codon 306 and sequencing showed point mutation in katG and rpoB gene. No mutation could be detected in the embB gene by multiplex allele specific PCR. The results indicates that further elaborate studies need to be carried out due to the presence of drug resistant M. tuberculosis in bovines which could be due to spill over from human in tuberculosis endemic areas making TB eradication programme more challenging.