Analysis of Antiphage Systems in Vibrio Cholerae O1 El Tor Biotype Strains

Abstract

Introduction: Cholera lytic phages contribute to the genetic diversity and evolution of Vibrio cholerae. To protect against the phages, the pathogen has acquired various resistance mechanisms. Objective: To identify antiphage systems located on mobile genetic elements in V. cholerae serogroup O1 El Tor biotype strains. Materials and methods: Nucleotide sequences of complete genomes of 77 toxigenic V. cholerae O1 El Tor strains imported to the Russian Federation and neighboring countries in 1970–2014 were analyzed using the Blast NCBI GenBank algorithm and REALPHY online tool. Results: We observed that the examined strains contained two types of anti-phage systems in hotspot 5 of the ICE SXT element: BREX, common for ICE VchBan9, and BREX with Abi typical of ICE VchInd5. We established a direct relationship between the presence of the PLE4 antiphage island and the kappa phage. V. cholerae O1 El Tor strains containing PLE4, except for one isolate, have BREX ICE VchBan9 and are grouped into a separate cluster in phylogenetic analysis. Strains with ICE VchInd5 lacking PLE4 and kappa phage also form a separate group. Conclusions: The data obtained on the presence of antiphage systems in previously imported strains of V. cholerae O1 biotype El Tor expand knowledge of their genetic organization. The study of the structure of antiphage genes of hotspot 5 of the ICE SXT element makes it possible to reveal genetic differences between closely related strains of V. cholerae O1 biotype El Tor and to determine the type of ICE SXT element.