[Features of biologic characteristics of Corynebacterium diphtheriae circulating in postepidemic period]

To study main biologic characteristics of C. diphtheriae strains circulating in North-West Region of Russia for the last 15 years.Six hundred and fifty strains of C. diphtheriae isolated from ill persons and carriers in Saint-Petersburg, Leningrad region and Vologda region at various periods of time were studied. Identification of an infectious agent was performed according to methodic guidelines MU 4.2698-98. IHA-chromatographic test (ICS-test) on the basis of MKA, polymerase chain reaction, determination of adhesive activity and susceptibility to antibiotics were performed.In recent years, circulation of C. diphtheriae strains with biologic characteristics similar to that observed in strains isolated during diphtheria epidemic and differed from that observed in strains isolated during the period of low incidence. Proportion of strains with "silent" gene between non-toxic in Elek-test C. diphtheriae increased. Decreasing of susceptibility to the range of antibiotics is observed in recent years.Revealed features of biologic characteristics of diphtheria agent circulating in post-epidemic period should be accounted during epidemiologic surveillance for diphtheria and choice of treatment of the infection.