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

Abstract

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 DeltaagfD 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.

Evolutionary loss of the rdar morphotype in Salmonella as a result of high mutation rates during laboratory passage

“…Development of lux-based reporters containing promoter regions cloned into a low-copy luciferase vector have been previously described for mlrA , agfD, agfB, adrA and s 70 (Stocki et al, 2007).…”

Attachment and Biofilm Formation by Salmonella in Food Processing Environments

“…Another study on colonization and persistence of Salmonella on egg conveyor belts indicated that the type of egg belt (i.e. vinyl, nylon, hemp or plastic) was the most important factor in colonization and persistence, while rdar morphotype, a physiological adaptation associated with aggregation and long-term survival which is conserved in Salmonella , surprisingly, was not essential for persistence (Stocki et al, 2007). Interestingly, inoculation onto fresh-cut produce surfaces, as well as onto inert surfaces, such as polyethersufone membranes, was found to significantly increase the survival of salmonellae during otherwise lethal acid challenge (pH 3.0 for 2 hours) (Gawande & Bhagwat, 2002).…”

Adaptation of Salmonella to Antimicrobials in Food-Processing Environments

“…For example, an S. Enteritidis strain isolated from an egg conveyor belt was found to be a source of persistent infection in poultry (Stocki et al, 2007). Similarly, Salmonella was able to persist in food bowls that had contained raw meat contaminated by this pathogen (Weese & Rousseau, 2006).…”