[Study of rifampicin resistance in L-forms of Mycobacterium tuberculosis, by analyzing rpoB gene mutations]

Twenty-nine Mycobacterium tuberculosis (MBT) L-form strains isolated from biopsy and surgery samples taken in 27 patients with extrapulmonary tuberculosis were studied. Since a direct examination of the resistance of L-forms is impossible due to their in vitro culturing features, it is expedient to use molecular genetic methods, by studying rpoB gene mutations. The study showed a high mutation rate (89.7%) in MBT L-forms associated with rifampicin resistance. The findings correlate with the recent years' monitoring of drug resistance in MBT in extrapulmonary tuberculosis, which has indicated that the total resistance of MBT from the foci of this form of tuberculosis to antituberculous drugs is as high as 90% and multidrug resistance is 30%. Moreover, the mycobacterial population was found to be heterogeneous. The ratio of rifampicin-resistant L-forms to sensitive ones in the established heterogeneity of the mycobacterial population calls for further studies.