P047

1:Institute of Pneumology "Chiril Draganiuc"; Chisinau, Moldova; 2:State University of Medicine and Pharmacy "nicolae Testemitamu"; Chisinau, Moldova

The aim: the concordances between the level of MIC and pattern of genotypic mutations for evaluation of DST of M. tb for correction of treatment.

Methods. In the study 6952 patients with new and previously treated pulmonary TB were examined for 2018-2020 years. Of these 66.2% positive by GeneXpert and 69.98% by culture method. The pDST result of 4865 M.tb strains from MGIT where correlated with gDST results obtained by MTBDRplus.  The mutation types in the rpoB gene, and the presence of inhA mutation in the same M.tb isolates was correlated correspondingly with the different level of MIC for RIFand INH of individual strains.

Results. INH resistance was found in 64% and RIF resistance in 62% of cases. From 157 isolates with presence of inhA mutations only in 31% were susceptible on higher MIC demonstrated by pDST. Among patients with genotypic RIF resistance with D516 mutation only, or without mutations and without wild genes, the phenotypic DST demonstrated that in 28.8% of cases these strains were susceptible to higher MIC. 

Discussion. Patients with low level genotypic resistance should have additional information about the level of phenotypic resistance. For reliable DST results, phenotypic and genotypic methods should be used in parallel, to be phased in without loss of existing solid culture and DST capacity.

Conclusion. pDST is still required, for corrective of rapid gDST results, in special from smear-negative specimens for detect XDR-TB. Different levels of phenotypic resistance could take into account in the procedures used by pDST of M. tb.