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Persistence of Salmonella on Egg Conveyor Belts Is Dependent on the Belt Type but Not on the rdar Morphotype

S. L. Stocki^*, C. B. Annett, C. D. Sibley, M. McLaws, S. L. Checkley, N. Singh, M. G. Surette^,|| and A. P. White^,1

^* Department of Biological Sciences, University of Calgary, Calgary T2N 4N1, Alberta, Canada; Alberta Agriculture and Food, 97 East Lake Ramp NE, Airdrie T6A 2B4, Alberta, Canada; Department of Microbiology and Infectious Diseases, University of Calgary, Calgary T2N 4N1, Alberta, Canada; Alberta Agriculture and Food, O. S. Longman Building, 6909-116 Street, Edmonton T6H 4P2, Alberta, Canada; and ^|| Department of Biochemistry and Molecular Biology, University of Calgary, Calgary T2N 4N1, Alberta, Canada

¹ Corresponding author: awhi{at}ucalgary.ca

Commercial caged layer flocks in Alberta, Canada, are commonly monitored for Salmonella enterica serovar Enteritidis (SE) and S. enterica serovar Typhimurium (ST) by environmental sampling. In one recent case, a SE strain isolated from the egg conveyor belt was a source of persistent infection for the flock. This study was undertaken to examine Salmonella colonization on egg conveyor belts and to determine whether the rdar morphotype, a conserved physiology associated with aggregation and long-term survival, contributed to persistence. Four woven belts constructed of natural or nonnatural fibers and a 1-piece belt made of vinyl were tested with rdar-positive ST and SE strains and a rdar-negative ST agfD reference strain. The type of egg belt was the most important factor influencing Salmonella colonization and persistence. The vinyl belt, with the least surface area available for colonization, had the fewest Salmonella remaining after washing and disinfection, whereas the hemp-plastic belt, with the greatest surface area, had the most Salmonella remaining. Real-time gene expression indicated that the rdar morphotype was involved in colonizing the egg belt pieces; however, it was not essential for persistence. In addition, rdar-positive and rdar-negative strains were equally similarly to disinfection on the egg belt pieces. The results indicate that Salmonella can persist on a variety of egg belts by mechanisms other than the rdar morphotype, and that using egg conveyer belts with reduced surface area for bacterial colonization can lessen contamination problems.

Key Words: thin aggregative fimbria • curli • rdar morphotype • persistence • egg conveyor belt