MIRU-VNTR genotyping of Mycobacterium tuberculosis strains from central region of Russia

Abstract number: P1553

Afanas'ev M., Ilina E., Smirnova T., Larionova E., Kuzmin A., Andreevskaya S., Chernousova L., Govorun V.

Objectives: The Russian Federation is one of the world's areas most affected by a high incidence of tuberculosis (TB). Although TB morbidity decreased slightly in recent years, the situation remains alarming due to a major increase in the incidence and prevalence of multidrug-resistant TB (MDR-TB). The purposes of this study were to evaluate epidemiological diversity and MDR spreading among M. tuberculosis strains, circulated in the Central region of Russian Federation.

Methods:M. tuberculosis strains (n = 35) from sputum of epidemiologically unrelated TB patients from Moscow were selected for study. Species identification and drug susceptibility testing to main antituberculosis drugs – rifampicin (RIF) and isoniazid (INH) – were performed according to the WHO recommended protocols. Standard procedure of MIRU-VNTR typing was carried out as described previously. For detection of specific SNPs causing drug resistance minisequencing reaction followed by matrix-assisted laser desorption/ionisation time-of-flight mass spectrometry (MALDI-TOF MS) of the reaction products was used.

Results: Among 65 M. tuberculosis strains 33 (50.8%) were identified as MDR (i.e. resistant to both RIF and INH), 19 (29.2%) were susceptible to RIF and INH, and 13 (20.0%) were resistant to INH only. Mutations in the RRDR of the rpoB gene were detected in all RIF-resistant strains. The Ser531Leu substitution was prevalent among them (24/33, 72.7%). Aberrations in the Ser315 codon of katG and/or in the inhA promoter region were found in 41 (89.1%) of 46 INH-resistant strains. Most of them (33/46, 71.7%) had the mutation Ser315Thr. Thirty five different MIRU-VNTR profiles were identified, including the 27 unique ones. 8 clusters (from 2 to 11 strains in each one) enclosed the 38 strains. Mutations associated with the MDR-phenotype were found more frequently in strains grouped in clusters (23/38; 60.5%), than for strains with unique MIRU-VNTR profiles (10/27; 37.1%). (Chi2 for trend 4.4; P < 0.05).

Conclusion: Those strains grouped into the main VNTR clusters and had the MIRU profiles 223325153533, 223325173533 or 223425173533 are associated with MDR-phenotype. It is possible that the spreading of such strains is related with secondary-acquired resistance and plays a significant role in increasing of MDR TB in the Central region of Russia.