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Abstract
Three studies were conducted to determine how Campylobacter spp. are capable of surviving on raw refrigerated poultry products and potentially cause human illness despite stresses it may encounter. The first study investigated the impact of carcass rinse and chicken exudate (weep) sampling on the recovery of Campylobacter spp. subtypes. It is important that sampling procedures provide subtype information indicative of human exposure. Our hypothesis was that sampling exudate allowed for the recovery of subtypes that may have been injured and non-culturable during the time of rinse. Three farms were sampled, collecting fecal samples and subsequent pre-chill rinse, post-chill rinse, 2-day exudate and 6-day exudate samples. Results suggest the same subtypes are not recovered by the two sampling procedures. This finding is important because different C. jejuni subtypes have been shown to have different virulence potentials. The second study investigated changes in transcriptome of C. jejuni in response to exposure to chicken exudate using expression microarrays. RNA was isolated from C. jejuni not exposed to exudate, after 15 minutes exposure and 1 hour exposure at 42C under microaerobic conditions. Several stress response genes including, clpB, grpE, groES, and ahpC, were identified as differentially expressed. In addition genes such as acnB, ppi and spoT, which are possibly involved in the regulation of other genes and possible virulence factors, were identified as differentially expressed. In the third study three C. jejuni isolates possessing mutations at genes identified as differentially expressed in the previous study (ahpC, clpB, spoT) were used to determine if expression of these genes influenced survival of C. jejuni in raw refrigerated poultry products. Both chicken skin and chicken exudate were used as substrates, and the levels of wild-type C. jejuni 11168 as well as the delta-ahpC,delta-clpB, and delta-spoT mutants were recorded at 0, 16, 24, 48, and 96 hours post inoculation. Results from the skin model suggest little difference in survival of the wild-type and the mutants, however, the chicken exudate model indicated that lack of expression of ahpC and spoT has an adverse effect on the survival of C. jejuni in raw refrigerated poultry products.