Heterogeneity of Antibiotic-Resistant Isolates of Listeria Monocytogenes Isolated from Food Products in Moscow

Abstract

Relevance. Listeria monocytogenes is a ubiquitous bacterium that causes listeriosis, which represents a widespread infectious disease currently inflicting great damage to livestock production and posing a serious threat to human health.Aim. To analyze the population structure and assess the pathogenic potential of Listeria monocytogenes isolates isolated on the territory of the Russian Federation.Materials and methods. A total of 79 listeria isolates were isolated from food products. Species identification and phenotypic analysis for antibiotic resistance were performed using VITEK MS system (bioMerieux, Marcyl’toile, France). Thirty-five antibiotic-resistant isolates were characterized by analysis of whole-genome sequencing data.Results. Whole genome sequences of thirty-five antibiotic-resistant Listeria monocytogenes isolates of food origin were analyzed. We determined clonal structure of this population and revealed a small number of antibiotic resistance determinants (fosX, tetM и сlpL), extensive set of virulence factors, as well as the presence of CRISPR/Cas systems. Most of the isolates belonged to phylogenetic line II and were divided into nine clonal complexes with the prevalence of CC121, which was one of the epidemiologically significant genetic clones. Two CC2 isolates belonging to the most pathogenic phylogenetic lineage I were also found. Thirteen isolates were characterized by the presence of putative CRISPR/Cas systems of IB and IIA types. All ST 121 isolates contained two types of identified adaptive immunity systems simultaneously in their genomes. Correlation analysis confirmed their functionality.Conclusion. We believe that the whole genome data obtained for the foodborne Listeria monocytogenes isolates will facilitate and complement further epidemiological studies of this pathogen, as well as the investigations of its genome variability in terms of the acquisition of various genetic elements associated with adaptation, antimicrobial resistance, and virulence. Moreover, the results of such studies will help to develop preventive measures to effectively solve problems associated with the bacterial contamination of animal products and ensure food safety in production conditions and the «farm-to-table» chain.