Yersinia enterocolitica-like strains: emerging pathogens in retailed fresh meat samples and their potential impact on public health

Abstract

Enterobacteria represent a diverse family of Gram-negative bacilli that are typically associated with the gastrointestinal tract of humans and animals, where they can act as commensals or pathogens. Among them, the genus Yersinia includes 19 species, with Y. enterocolitica and Y. pseudotuberculosis recognized as significant enteric pathogens, while Y. pestis causes plague. Yersinia species are globally distributed but are most prevalent in temperate and cold climates, ranking as the third leading cause of bacterial diarrhea in Europe. Transmission is primarily through contaminated food, such as raw pork or unpasteurized milk. This study describes a protocol for isolating and identifying Yersinia strains from food samples, focusing on enrichment and selective culture techniques followed by rapid identification using MALDI-TOF mass spectrometry. Enrichment in ITC broth, recommended by ISO10273, and subsequent isolation on SSDC selective media enabled the recovery of distinct Yersinia colonies. MALDI-TOF provided species-level identification based on protein spectral analysis, with a scoring system ensuring accuracy. Application of this protocol to fresh meat samples led to the isolation of Yersinia frederiksenii, a species previously identified in various environmental and animal sources. This study highlights the utility of combined enrichment, selective culturing, and MALDI-TOF for studying Yersinia in food microbiology and zoonotic disease research.