Preliminary Study of the Characterization of the Viable but Noncultivable State of Yersinia enterocolitica Induced by Chloride and UV Irradiation

Abstract

The viable but non-culturable (VBNC) state is a survival strategy for many foodborne pathogens under adverse conditions. Yersinia enterocolitica (Y. enterocolitica) as a kind of primary foodborne pathogen, and it is crucial to investigate its survival strategies and potential risks in the food chain. In this study, the effectiveness of ultraviolet (UV) irradiation and chlorine treatment in disinfecting the foodborne pathogen Y. enterocolitica was investigated. The results indicated that both UV irradiation and chlorine treatment can induce the VBNC state in Y. enterocolitica. The bacteria completely lost culturability after being treated with 25 mg/L of NaClO for 30 min and a UV dose of 100 mJ/cm². The number of culturable and viable cells were detected using plate counting and a combination of fluorescein and propidium iodide (live/dead cells). Further research found that these VBNC cells exhibited reduced intracellular Adenosine Triphosphate (ATP) levels, and increased levels of reactive oxygen species (ROS) compared to non-induced cells. Morphologically, the cells changed from a rod shape to a shorter, coccobacillary shape with small vacuoles forming at the edges, indicating structural changes. Both condition-induced VBNC-state cells were able to resuscitate in tryptic soy broth (TSB) medium supplemented with Tween 80, sodium pyruvate, and glucose. These findings contribute to a better understanding of the survival mechanisms of Y. enterocolitica in the environment and are of significant importance for the development of effective disinfection strategies.