Molecular epidemiology of diphtheria

Molecular subtyping of Corynebacterium diphtheriae identified significant g enetic diversity within the species and led to the identification of a uniq ue clonal group that emerged in Russia in 1990 at the beginning of the curr ent epidemic. Strains of this group belong to a distinct electrophoretic ty pe complex and are of ribotypes D1 and D4. Identification of the group allo wed for precise monitoring of the epidemic's progression and for rapid dete ction of cases imported to other countries. The evolution of this clonal gr oup was monitored, and changes were identified. Molecular analysis revealed that no amino acid substitutions have occurred in the diphtheria toxin gen e of the epidemic clone strains, reaffirming the use of the current vaccine as the single most effective preventive measure. Application of molecular subtyping methods and continuous monitoring of the spread of these clones h as made it possible to distinguish rapidly between epidemic, endemic, and i mported cases, allowing for implementation of timely and adequate preventiv e measures and providing reassurance that no secondary spread resulted from importations.