Use of an Autobioluminescent Campylobacter jejuni to Monitor Cell Survival as a Function of Temperature, pH, and Sodium Chloride

Abstract

The effects of storage temperature (4, 22, and 30°C), pH (4.0 to 8.5), and sodium chloride concentration (0.25 to 7.5%, wt/vol) on the survival of a strain of Campylobacter jejuni ATCC 35921 with an autobioluminescent phenotype (generated from the fusion of luxCDABE genes from Xenorhabdus luminescens to the C. jejuni flaA promoter) in Mueller-Hinton broth under aerobic conditions were determined. At comparable pHs, autobioluminescent C. jejuni cells die most rapidly at 30°C and most slowly at 4°C. For example, at pH 5.5, a 1.2-log decrease in the cell count was observed after 4 days of storage at 4°C, while 3.7- and 4.8-log reductions in cell numbers were observed after 4 days of storage at 22 and 30°C, respectively. At 4°C, C. jejuni was sensitive to NaCl concentrations of ≥2.5%. However, the degree of inactivation at this storage temperature was also significantly lower than that observed at 22°C, which, in turn, was substantially lower than that observed at 30°C. In the presence of different NaCl concentrations at 22 and 30°C, a strong correlation (r = 0.98) between plate count and bioluminescence output was obtained. However, at low pHs (4.0 and 4.5) and/or a low storage temperature (4°C), bioluminescence did not correlate well with plate count. Despite these limitations, an autobioluminescent phenotype of C. jejuni proved to be a useful tool for studying the behavior of C. jejuni exposed to environmental stresses.