Cold Enrichment Methods for the Detection of Foodborne Yersiniosis: Friend or Foe?

Yuwei Zhang,Stephen L W On

doi:10.3390/pathogens11020278

Abstract

Yersinia enterocolitica and Y. pseudotuberculosis are important causes of enteric illness worldwide. Rapid response to suspected foodborne outbreaks is hampered by the widespread use of cold enrichment methods that require incubation periods of 10–21 days. Although these species grow faster at elevated temperatures, part of the rationale for cold enrichment is that a key pathogenicity marker (pYV virulence plasmid) is said to be lost at elevated temperatures. Experimental data on this claim seems scarce. We previously described an approach involving an enrichment step at 37 °C for Yersinia detection, applied this approach to additional strains, and examined the presence of plasmids in reisolates, as well as those recovered in our original study. Plasmids were recovered from every reisolate examined; the presence of marker genes yadA and virF denoted the virulence plasmid in 10 of the 11 strains examined. Use of an enrichment step at 37 °C does not appear to promote loss of the pYV or other plasmids harboured by foodborne pathogenic Y. enterocolitica and Y. pseudotuberculosis; wider adoption of this approach may assist the development of more rapid detection methods.

Highlights

In several countries, the enteric disorder yersiniosis caused by Yersinia enterocolitica or Y. pseudotuberculosis is among the most frequently reported foodborne diseases, representing a substantive public health burden [1,2,3,4]
Optimal characterisation of an outbreak caused by pathogenic Yersinia species may not be achieved where such an important virulence trait is lost, especially when pathogenicity genes located on the plasmid can be targets for PCR detection approaches [5]
The widespread use of the cold enrichment approach to the detection of foodborne Yersinia species may, in part, be due to statements in influential reference books that state “virulent plasmid-containing strains of Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica rapidly become avirulent when grown at 37 ◦C, which results in the loss of the virulence plasmid” [6]

Summary

Introduction

In several countries (including New Zealand), the enteric disorder yersiniosis caused by Yersinia enterocolitica or Y. pseudotuberculosis is among the most frequently reported foodborne diseases, representing a substantive public health burden [1,2,3,4] Detection of these species is hampered by poorly effective methods, most frequently involving cold (4–10 ◦C) enrichment approaches for prolonged (10–21 days) periods [5], that are clearly inadequate for rapid outbreak detection. The reviewer suggested “Most colonies obtained from the unadulterated nutrient-enrichment method, may not be pathogens.” Such a viewpoint is clearly widespread: an extensive review of Yersinia detection methods does not describe a single culture approach utilising any temperature higher than 30 ◦C [5]. The strain prefixes of EWP, PT and PB are of unknown affiliation and are reproduced as received

Discussion

Strains Used

Culture Methods

Plasmid DNA Isolation and Detection

PCR Analysis