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

Abstract

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.