katG mutations in isoniazid-resistant strains of Mycobacterium tuberculosis isolates from Belarusian patients

The aim of this study was to investigate the frequency, location and type of katG mutations in Mycobacterium tuberculosis strains isolated from patients in Belarus. Mutations in different codons causing resistance to isoniazide in the gene of catalase peroxides (katG) in Belarusian strains was determined. 42 strains of Rif-r and Inhr(MDR) were isolated in different regions of Belarus. Culture susceptibility testing of all 42 strains revealed resistance to streptomycin (90%), 16 strains (43%) were resistant to etambutol. DNA Extraction, Standard PCR identification and katG gene amplification were performed. The most affected codons of katG gene were 315(95%), 316(16.2%), and 309(14.5%). Four types of mutations were identified in codon 315: AGC-->ACC (n=36)32.4%, AGC-->AGG (n=1) 0.9%, AGC-->AAC (n=2) 1.8%, AGC-->GGC (n=1) 0.9%. One type of mutation was found in codon 316: GGC-->AGC (n=18)16.2%, four types of mutations were detected in codon 309: GGT-->GGT (n=7)6.3%, GGT-->GCT (n=4)3.6%, GGT-->GTC (n=3)2.7%, GGT-->GGG (n=1)0.9%. Mutations in codon 309 make up 34%, in codon 316 (37%) and other types of mutations 29% of all detected mutations. In 2 isolated strains mutation were identified in codons 463, 35 and, in codons 454, 357 respectively and 2 isolates, there were not found any mutations. Concluding, all INH-r MBT had resistance-associated nucleotide changes mostly in codons 315.