Title: Radiation resistance and loss of crystal violet binding activity in Y. enterolitica suspended in raw ground pork exposed to gamma radiation and modified atmosphere Authors
Submitted to: Journal of Food Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 21, 2014
Publication Date: N/A
Interpretive Summary: Yersinia enterocolitica, a bacterium which can cause severe intestinal distress when consumed in contaminated food, is of particular concern due its ability to grow at refrigeration temperatures. Disease is caused by those strains of bacteria which contain a 70-kb virulence plasmid (pYV). Prior research suggested that the capability of pYV to cause disease could be impaired by conditions similar to those that occur during the processing, packaging, and cooking of foods. This study established that gamma radiation inactivation D10 data for pathogenic Y. enterocolitica irradiated under modified atmosphere can provide information to risk assessors regarding the difference between pathogen presence versus virulence. These results, using Y. enterocolitica as a model system, indicate that the risk of foodborne illness could be affected by the loss of virulence factors when post-process intervention technologies are used. Most importantly, this study highlights the importance of actual virulence of foodborne pathogens, as opposed to mere presence, when assessing risk of actual foodborne illness. The results of this study indicate that the combination of atmosphere and irradiation reduces the ability of pathogenic Y. enterocolitica to infect humans.
Technical Abstract: The virulence of many foodborne pathogens is directly linked to genes carried on plasmids, self-replicating extra-chromosomal elements, which can transfer genetic material, both vertically and horizontally, between bacteria of the same and different species. Pathogenic Yersinia enterocolitica harbors a 70-kb virulence plasmid (pYV) that encodes genes for low calcium response, crystal violet (CV) binding , Congo red uptake , autoagglutination (AA), hydrophobicity (HP), type III secretion channels, host immune suppression factors, and biofilm formation. Ionizing (gamma) radiation and modified atmosphere packaging (MAP) are used to control foodborne pathogens and meat spoilage. In this study the effect of gamma radiation and modified atmosphere (air, 100% N2, 75% N2: 25% CO2, 50% N2: 50% CO2, 25% N2, 75% CO2, 100% CO2) were examined by using the CV binding phenotype, for the presence or absence of pYV in Y. enterocolitica, suspended in raw ground pork. All three Y. enterocolitica serovars used (O:3, O:8 and O5,27) were more sensitive to gamma radiation as the CO2 concentration increased above 50%. Crystal violet binding following a radiation dose of 1.0 kGy, which reduced the Y. enterocolitica serovars > 5 log, was greatest in the presence of air (ca. 8%), but was not affected by N2 or CO2 concentration (ca. 5%). Following release from modified atmosphere after irradiation, the loss of CV binding rose from 5 - 8% immediately following irradiation to > 30% after outgrowth at 25 degrees C for 24 hr. These results, using Y. enterocolitica as a model system, indicate that the risk of foodborne illness could be affected by the loss of virulence factors when post-process intervention technologies are used.