Impacts of treatment parameters on the inactivation of Campylobacter jejuni by high pressure: a statistical study of main effects and interactions

The influence of environmental (temperature and pH) and biological (strain) parameters on the inactivation of Campylobacter jejuni by high hydrostatic pressure (HHP) was investigated. Two clinical strains harvested in stationary phase were pressurized at 20 degrees C and 37 degrees C within a range of 50-400 MPa, in a phosphate (pH 7.0) or a citrate phosphate buffer (pH 5.6), for 10 min. Treatment efficiencies were determined by logarithmic comparisons of culturable cells on blood agar before and after treatment. Results were statistically compared using an anova of culturable cells after treatment to evaluate the effect of all factors. At least a 7-log reduction in cell numbers was observed for both strains. The pH and the strains had no effect on HHP treatment at 20 degrees C while at 37 degrees C, both pH and strain influenced significantly the HHP treatment on C. jejuni. The pressure efficacy on C. jejuni eradication was affected by both environmental and biological factors. Depending on the treatment conditions, C. jejuni sensitivity to HHP can significantly vary. The determination of the inactivation treatment by HPP has to be normalized considering the interaction of environmental and biological factors.