IMPROVEMENT OF GISSA MEDIUM WITH STARCH AND ANDREDE INDICATOR FOR BACTERIOLOGICAL EXAMINATION FOR DIPHTHERIA INFECTION

Diphtheria continues to be relevant diseases even in countries with many years of mass vaccine prevention. The greatest concern is the situation in the African region, where the increase in cases and deaths from diphtheria has continued since the beginning of 2023. In the Russian Federation, no cases of diphtheria and bacterial carriers were registered in 2023. In this regard, the risk of imported cases of diphtheria to the territory of our country remains. Therefore, in order to maintain a favorable situation for diphtheria, it is necessary to maintain a qualitative level of bacteriological diagnostics with all tests by regulatory documents, including the determination of toxigenicity and biovar of the pathogen. Purpose. Modification of the recipe for the preparation of the Andrede indicator and Gissа medium with starch to determine the biovar C. diphtheriae. Material and methods. Control toxigenic strains of C. diphtheriae biovar gravis № 665, toxigenic strain of C. diphtheriae biovar mitis № 6765, toxigenic strains of C. ulcerans № 675 and 7819, C. pseudodiphtheriticum Sokolov, strain Staphylococcus aureus were used 25923, as well as wild toxigenic strains of C. diphtheriae and C. ulcerans. The strains were cultured in accordance with MU 4.2.3065-13 and 4.2.3852-23 «Laboratory Diagnostics of Diphtheria Infection». Results and discussion. Studies were carried out to develop a modernized recipe for preparing the Andrede indicator for determining starch fermentation in the identification of biovar of the causative agent of diphtheria infection. The results of comparative studies with the Andrede indicator prepared according to the previously proposed recipe and an upgraded version using a chemical reagent-starch from four manufacturers are presented. The shelf life of the finished Gissа medium with the Andrede indicator in the laboratory was determined. Conclusion. The modernized recipe for the Andrede indicator and the preparation of Gissа medium with starch will increase the efficiency and eliminate errors in the identification of biovar in C. diphtheriae. © 2025 Elsevier B.V., All rights reserved.