Use of luminescent Campylobacter jejuni ATCC 33291 to assess eggshell colonization and penetration in fresh and retail eggs

A luminescent phenotype in Campylobacter jejuni ATCC 33291, generated by a transcriptional fusion between the C. jejuni flaA sigma (28) promoter and the luxCDABE genes of Xenorhabdus luminescens on plasmid pRYluxCDABE, was used to examine colonization and penetration of fresh and retail eggs. C. jejuni colonized both fresh and retail eggs at 37, 40, and 42 C under microaerophilic conditions. Fresh eggs were more heavily colonized than retail eggs. Under aerobic conditions. fresh eggs were colonized at similar levels for all three temperatures. C. jejuni was found to penetrate the eggshell in 2 of 48 (4.2%) fresh eggs assessed. Although the lux(+) phenotype did not provide an effective means of predicting penetration sites, it was effective at visualizing eggshell colonization. Also, it effectively demonstrated the organism's opportunistic nature, as eggshell surfaces with flaws and slight cracks were extensively colonized and easily detected by a photon counting charge-coupled device camera. Using scanning electron microscopy, C. jejuni ATCC 33291 was visualized on both the exterior and interior surfaces of the egg membranes indicating penetration of these barriers.