The First Finding of Francisella Tularensis Subsp. Mediasiatica in Krasnoyarsk Territory, Siberia and an Update of the Subspecies Genetic Diversity

Tularemia is a severe infectious disease caused by the Gram-negative bacteria Francisella tularensis. F. tularensis is currently divided into three subspecies, holarctica, tularensis and mediasiatica which differ in their virulence and geographic distribution. Subspecies mediasiatica is the least studied because of its very low documented virulence for humans and limited geographic distribution. It was discovered in sparsely populated regions of Central Asia. Since 2011, a new subsp. mediasiatica lineage was identified in Altai (Russia). In 2021, we isolated one subsp. mediasiatica strain in Krasnoyarsk Territory. In spite of its geographic origin, 500 km east from Altai, this strain belongs to the Altai lineage and contributes surprisingly little genetic diversity to previous knowledge. This improved knowledge of the phylogeography of subsp. mediasiatica led us to propose a scenario in which the two zoonotic lineages, holarctica and tularensis, independently emerged from the mediasiatica lineage in Siberia or Central Asia, and make predictions which will allow to challenge this hypothesis