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Vol 58(2024) N 6 p. 1089-1100; DOI 10.1134/S0026893324700596 N.B. Polyakov1,2, D.S. Karpov3, M.V. Zubasheva1*, A.N. Polyakova4, D.N. Shcherbinin1, A.I. Solovyev1, M.V. Lavrentiev1, T.A. Smirnova1, M.A. Sukhina5, V.G. Zhukhovitsky1,6 Identification of the Clinical Isolate CCGC 19/16 as Bacillus cytotoxicus 1Gamaleya National Research Centre for Epidemiology and Microbiology, Ministry of Health of the Russian Federation, Moscow, 123098 Russia2Vernadsky Institute of Geochemistry and Analytical Chemistry, Russian Academy of Sciences, Moscow, 119334 Russia 3Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Engelhardt Institute of Molecular Biology, Russian Academy of Sciences, Moscow, 119991 Russia 4Moscow State University, Moscow, 119234 Russia 5Ryzhikh National Medical Research Center of Coloproctology, Ministry of Health of the Russian Federation, Moscow, 123423 Russia 6Russian Medical Academy of Continuing Professional Education (RMANPO), Ministry of Health of the Russian Federation, Moscow, 125993 Russia * mzubasheva@mail.ru Received - 2024-04-23; Revised - 2024-04-23; Accepted - 2024-05-20 Bacillus cereus sensu lato comprises genetically, morphologically, and physiologically similar gram-positive spore-forming bacterial species with high pathogenic potential, such as B. anthracis, B. cereus, and B. thuringiensis. Toxin-producing strains of B. cereuss.l. pose a major threat to human health. The high degree of similarity between these species makes it very difficult to identify them and to take adequate measures to treat the diseases they cause. Previously, we characterized the clinical isolate CCGC 19/16 belonging to B. cereus s.l. that exhibited features of both B. cereus and B. cytotoxicus. In the present work, CCGC 19/16 was identified as B. cytotoxicus using multilocus sequence typing (MLST) and mass spectrometric analysis. It was also shown that, unlike other representatives of the B. cytotoxicus species, strain CCGC 19/16 is not thermotolerant. Unlike B. cereus, strain CCGC 19/16 is sensitive to most antibiotics and shows increased motility. Like B. cereus strain CCGC 19/16 forms β-hemolysis zones in blood agar. In addition, it has been shown that prolonged storage of samples prior to analysis can lead to misidentification of the isolate. Our results indicate that "rapid methods" of analysis using single genes have insufficient resolving power in the identification of B. cereus s.l. species. The combination of MLST analysis with MALDI-TOF MS provides sufficient resolution. Bacillus cereus group, Bacillus cytotoxicus, mass spectrometry, MLST |