Effect of Temperature on Viability of Campylobacter jejuni and Campylobacter coli on Raw Chicken or Pork Skin

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To determine growth and survival of Campylobacter jejuni and Campylobacter coli on chicken and pork, Campylobacter spp. (104 CFU/cm2) were inoculated on pieces of raw, irradiated chicken or pork skin and exposed to temperatures ranging from −20 to 42°C under either microaerobic or aerobic conditions. Viable counts over 48 h declined 2 to 3 log CFU/cm2 at −20°C and 1 to 2 log CFU/cm2 at 25°C regardless of skin type, species of Campylobacter, or level of oxygen. At 4°C, there was no significant change in the number of Campylobacter over 48 h. At both 37 and 42°C, the number of viable Campylobacter increased significantly (2 to 3 log CFU/cm2, P < 0.0001) under microaerobic conditions but decreased 0.5 to 1.5 log CFU/cm2 in air. Preincubation of skins for 24 h at 42°C under microaerobic conditions to establish Campylobacter on the surface prior to lowering the temperature to −20, 4, or 25°C and incubating in air resulted in a decline in viability for the first 4 h (0.5 to 1 log CFU/cm2). However, after this initial drop in viability, no additional effect on viability was observed compared with incubation at −20, 4, or 25°C in air without microaerobic preincubation at 42°C. Preincubation of inoculated skins at −20, 4, or 25°C in air for 24 h followed by a shift in temperature to 42°C for 4, 8, 24, or 48 h and a shift to microaerobic conditions resulted in an overall decline in viability on raw pork skin but not on raw chicken skin. In contrast, preincubation of inoculated skins at −20, 4, or 25°C for 24 h in air followed by a shift in temperature to 37°C and microaerobic conditions did not result in a decrease in viable counts for either chicken or pork skins. Overall, viability of C. coli and C. jejuni on chicken and pork skins was similar. Therefore, a lower incidence of Campylobacter spp. in pork than in poultry postslaughter, despite a similar prevalence in live animals, is not due to differences in viability of C. coli versus C. jejuni on raw chicken or pork skin.