STUDYING OF MOLECULAR MECHANISMS OF RESISTANCE OF CORYNEBACTERIUM DIPHTHERIAE STRAINS TO RIFAMPICIN

O.Yu. Borisova, I.A. Chagina, V.A. Aleshkin
G.N. Gabrichevsky Institute of Epidemiology and Microbiology, Admirala Makarova str., 10, Moscow, 125212, Russian Federation
E-mail: olgborisova@mail.ru

Introduction. Penicillins and macrolides are applied for the treatment of both diphtheria carriers, in the comprehensive therapy of separate forms of diphtheria, and patients with invasive diseases caused by nontoxigenic C. diphtheriae. In the 1990s there was shown the high efficiency of rifampicin either. The inefficiency of a treatment can speak about the congenital or acquired disturbance of the resistance of mucosas, dysbiosis of a stomatopharynx and nose, and resistance of strains of C.diphtheriae to antibiotics. Purpose was to estimate an antibiotic susceptibility and molecular mechanisms of the resistance of C.diphtheriae strains to rifampicin. Material and methods. 664 strains of C.diphtheriae isolated in 1987–2014 in various regions of Russia were studied. The determination of an antibiotic susceptibility of C. diphtheriae strains are studied by the disco – diffusive and the E-test method. Results. Molecular mechanisms of the resistance were established be means of the primer – specific PCR. The majority of strains was shown to be sensitive to rifampicin, 0,15% of strains had an intermediate level of the resistance and 4,7% of strains seem to be resistant (41,9% of strains were completely resistant and 58,1% of strains had MIC of 16–32 mkg/ml). The resistance of C.diphtheriae strains was established to be caused by the existence of mutations in rpoB gene. Mutations are revealed in 29 positions out of which in 26 positions of a mutations weren't followed by changes at the amino-acid level. In three positions – 1291, 1307 and 1484 significant mutations followed by changes at the amino-acid level – H431N; S436F or S436Y, P495L or P495Q are revealed to be localized in the 1 cluster of rpoB gene. Conclusion. In the territory of the Russian Federation resistant C.diphtheriae strains to rifampicin circulate in 4.7% cases. The molecular mechanism of the resistance of C.diphtheriae strains caused by mutation changes in three positions of a gene rpoB (1291, 1307 and 1487) have been described for the first time.
Keywords: 
Corynebacterium diphtheria; rifampicin; resistance; mutations