Kinetic Behavior of Campylobacter jejuni in Beef Tartare at Cold Temperatures and Transcriptomes Related to Its Survival

Abstract

This study was conducted to examine the kinetic behavior of Campylobacter jejuni in raw beef tartare by using mathematical models and to identify genes related to C. jejuni survival at cold temperatures. C. jejuni was inoculated onto beef tartare samples, stored at 4, 10, 15, 25, and 30 degrees C, plated on modified charcoal-cefoperazone-deoxycholate agar, and enumerated. The survival data was fitted to the Weibull model to calculate delta (delta), which is the time required for the first 1-log reduction of the cells. The Davey model was then fitted to the delta to evaluate the effect of temperature. To evaluate the performance of the developed model, the root mean square error (RMSE) was calculated by comparing the observed data with the predicted data. The mRNA was extracted from samples stored at 4 and 30 degrees C under aerobic and anaerobic conditions, and the expression of oxidative stress response and stress response genes was evaluated. C. jejuni survived in beef tartare longer at 4 degrees C (delta = 657.1 +/- 79.6 min) than at other temperatures (9.7 +/- 11.2 to 465.7 +/- 139.3 degrees C) even under aerobic conditions. The RMSE (0.475) suggested that the developed model was appropriate to describe the kinetic behavior of C. jejuni. Quantitative real-time PCR results revealed that oxidative stress and stress response genes were related to C. jejuni survival at cold temperatures, even under aerobic conditions. These results indicate that the model will be useful for describing the kinetic behavior of C. jejuni in beef tartare and that this pathogen can survive at cold temperatures because of the expression of the sodB, katA, and clpP genes.