| Abstract [eng] |
Genotyping of Mycobacterium tuberculosis and research on mutations conferring resistance to drugs Rūta Kudarauskaitė SUMMARY Tuberculosis situation in Lithuania is one of the worst in European Society. The aim of this work was to carry out genotyping of M. tuberculosis strains and to search for mutations conferring resistance to ofloxacin, streptomycin, kanamycin, amikacin and para-aminosalicylic acid that would lead to better understanding mechanisms of origin and spread of drug-resistant tuberculosis. In total, collection of 852 M. tuberculosis strains was investigated by using internationally standardized genotyping procedure of spoligotyping. The specific spoligotype signatures, genetic sublineages and their lineages were identified. The most prevalent were strains that belonged to sublineages Beijing (24.4%), Haarlem 4 (21.3%), T1 (21.1%), LAM 9 (8.8%) and Haarlem 1 (4.2%). Analysis revealed that 64.6% of M. tuberculosis strains belonged just to seven of 123 identified spoligotypes: ST1, ST35, ST42, ST47, ST53, ST262 ir ST766. As the result of spoligotyping the presence of large groups of highly virulent and genetically related strains have been confirmed by another independent method of genotyping. Forty-one ofloxacin-resistant and 72 kanamycin-resistant isolates were searched for resistance conferring mutations and results of the tests were incorporated into continuing studies on prevalence of these mutations. In total, 82.4% of 108 ofloxacin-resistant M. tuberculosis isolates carried mutations in gyrA or gyrB genes; 14.9% of 141 kanamycin-resistant and 34.4% of 48 amikacin-resistant isolates had mutations in 3’region of rrs gene. In total, 84.74% of 590 streptomycin-resistant M. tuberculosis isolates carried mutations in rrs and rpsL genes and 59.12% of 181 M. tuberculosis isolates carried mutations in gidB gene associated with low level of streptomycin resistance. Out of 25 PAS-resistant isolates M. tuberculosis strains tested 60% carried resistance conferring mutations in the thyA gene and none of them had mutations in dfrA gene. A study on mutations in putative mutator genes was performed by investigation representative collection of the most prevalent genotypes of M. tuberculosis. Analysis revealed that 98% of strains that belonged to Beijing family have specific mutations in mutT2, mutT4, and ogt genes simultaneously and strains of Haarlem 1 and 3 sub lineages carry specific mutations in ogt and ung genes. |
