Survival and genomic stability of Yersinia enterocolitica in environmental Acanthamoeba spp

Paola Chiani^1*Valeria Michelacci¹Elisabetta Delibato¹Eleonora Ventola¹Samra Mannan¹Manuela Marra¹Valentina Libri¹Rubén L. Rodríguez-Expósito²M Reyes-Batlle²I De Fuentes³Jacob Lorenzo-Morales²Stefano Morabito¹Margherita Montalbano Di Filippo¹

• ¹National Institute of Health (ISS), Rome, Italy
• ²Universidad de La Laguna Facultad de Ciencias de la Salud, San Cristóbal de La Laguna, Spain
• ³Instituto de Salud Carlos III, Madrid, Spain

Free-living amoebae (FLA) are widespread protozoa that can host bacterial pathogens, promoting their persistence in the environment. Yersinia enterocolitica, a foodborne zoonotic pathogen, has been detected within amoebae, but its intracellular dynamics remain unclear. In this study, we explored the interaction between three Y. enterocolitica strains - differing in biotype and virulence gene profile - and two Acanthamoeba spp.: a reference strain and a wild environmental isolate. All strains were internalized and survived up to 8 days in the collection strain and 16 days in the wild isolate. Intracellular persistence did not affect amoebal integrity or bacterial virulence profiles. Whole genome sequencing (WGS) revealed high genomic stability across strains, though specific mutations - such as in igaA gene, involved in stress response - emerged after persistence in the collection strain. These findings suggest that Acanthamoeba spp. not only shields Y. enterocolitica from environmental stress but may also influence its genome and adaptive potential. This work expands the current understanding of Y. enterocolitica biology and highlights the role of FLA as reservoirs and potential drivers of bacterial evolution. Their contribution to the bacteria persistence and gene exchange warrants further investigation, particularly in the context of antimicrobial resistance and food safety.