Location: Egg Safety and Quality
Title: Molecular Characterization and Serotyping of Salmonella Isolated from the Shell Egg Processing Environment Authors
Submitted to: Journal of Food Protection
Publication Type: Abstract Only
Publication Acceptance Date: May 6, 2010
Publication Date: N/A
Technical Abstract: ABSTRACT BODY: Introduction: Salmonellosis may be contracted by the consumption of raw or undercooked eggs. In order to develop effective sanitation practices it is helpful to understand the location of Salmonella reservoirs in processing environments. Shell egg processing reservoirs for Salmonella have not been well characterized, previously. Purpose: A study was conducted to determine which equipment and facility surfaces in the shell egg processing environment were contaminated with Salmonella. Isolates were further characterized to determine serotype and relative molecular similarity. Methods: On 7 visits, 35 surfaces were swabbed individually using sterile gauze pads soaked in 10 mL of phosphate buffered saline. Each sample was subjected to a cultural procedure to recover Salmonella: pre-enrichment in buffered peptone overnight at 37°C, selective enrichment in TT and RV broths at 42°C for 18-24 h, selective plating (BGS and XLT-4) incubated at 37°C for 18-24 h, biochemical reactions (LIA and TSI slants) incubated at 37°C for 18-24 h,and confirmed using poly-clonal anti-sera. Isolates were re-streaked three times and saved prior to subsequent analyses. Isolates were sero-typed by the Kauffman-White scheme. DNA from each isolate was harvested and purified using a commercial kit. DNA was analyzed by repetitive Enterobacteriaceae palindrome polymerase chain reaction using an automated system. Scatter plots and dendrograms were created to visualize DNA similarity. Results: Salmonella serotypes recovered were Braenderup (1), Kentucky (2), Heidelberg (12), Typhimurium Copenhagen (Tyco-1), and Typhimurium (7). Salmonella-positive surface locations were wash tanks (Kentucky, Typhimurium, Tyco), drains (Braenderup, Heidelberg), and post-wash equipment surfaces (Heidelberg, Kentucky). All Typhimurium were recovered from the wash tanks at a single rep and were similar (95%). Drain isolates were similar regardless of rep (90%). Almost 70% of the isolates were recovered from wash tank equipment surfaces from 2 reps. However, drains were a Salmonella reservoir in 4/7 reps. Significance: Wash tanks and drains were important Salmonella reservoirs in the shell egg processing environment. These results indicate that more effective sanitation is needed for washing equipment surfaces and drains.