Ecological and genetic mechanisms of development of epidemiologically significant strains of sapronosis causative agents

Abstract

Sapronosis is an infectious disease caused by pathogenic microorganisms that are natural inhabitants of soil and/or aquatic ecosystems. They are capable of exiting in the environment outside of the host for a long time. Causative agents of sapronosis are polypathogenic, i.e., they cause infections in a wide range of hosts. The aim of the work was to establish a place in the clonal species structure for Listeria monocytogenes and Yersinia pseudotuberculosis isolated from both patients in hospitals and wild rodents and hydrobionts in natural foci. A total of 42 L. monocytogenes and 29 Y. pseudotuberculosis isolates were studied. 17 L. monocy-togenes and 29 Y. pseudotuberculosis isolates were obtained from patients; 25 L. monocytogenes isolates were obtained from wild animals and soil. The isolates were characterized using Multilocus Sequence Typing (MLST). Previously published MLST schemes were applied, including an analysis of the sequences of internal regions of seven marker genes for general metabolism. All Y. pseudotuberculosis isolates were shown to belong to the clonal complex occurred in the Russian Far East, Japan, and China, while L. monocytogenes isolates were referred to several clonal complexes, some of which have a worldwide distribution. The genetic similarity between L. monocytogenes isolates that cause invasive infections in wild animals in natural listeriosis foci and isolates related to listeriosis outbreaks has been demonstrated. These results suggested that high virulence could be a selective trait that enables the efficient reproduction of sapronosis causative agents in natural ecosystems. The variability of virulence factors of L. monocytogenes isolated from the same natural focus and related to MLST type was indicated. A hypothesis has been suggested that links the polyhostality of sapronosis causative agents and the genetic variability in virulence factors. Based on this hypothesis, a correlation has been suggested between the sequences of virulence factors and the source of isolation. A model of the formation of epidemiologically significant strains of the causative agents in natural foci of sapronosis was constructed.