ENTEROBACTERIACEAE AND RELATED ORGANISMS ISOLATED FROM SHELL EGGS WASHED IN COOLER WASH WATER

Authors: Musgrove, Michael; Jones, Deana

Submitted to: Poultry Science
Publication Type: Abstract Only
Publication Acceptance Date: 5/21/2006
Publication Date: 7/17/2006
Citation: Musgrove, M.T., Jones, D.R. 2006. Enterobacteriaceae and related organisms isolated from shell eggs washed in cooler wash water. Poultry Science Annual Meeting. p. 135

Interpretive Summary:

Technical Abstract: Processing guidelines in 7 CFR part 56 dictate that shell eggs be washed in water at 32- 49 C. As they pass through the dual commercial washers, egg temperatures often rise to levels conducive to bacterial growth. A commercial study was conducted to determine if washing eggs with cooler water would allow for reduced egg temperatures and preserve microbiological quality. An in-line and on off-line facility were each sampled on 3 visits. Wash water treatments observed were: HH = 49C, 49C; HC = 49C, 24 C; and CC = 24 C, 24 C. On each visit, four 3-egg pools per treatment were sampled by crushing shells and membranes with 30 mL of phosphate buffered saline. Enterobacteriaceae were detected by pour-plating shell/membrane homogenates using violet red bile glucose agar. Plates were incubated at 37 C for 24 h and 5 isolates per positive sample were randomly selected, streaked three times to ensure purity, and identified to genus level using biochemical testing. Shell surface temperatures for the 3 treatments (HH, HC, CC) averaged 26.2, 22.7, 21.2 C for in-line eggs and 20.2, 18.6, and 17.2 C for off-line eggs. Identifications were made for 257 in-line and 45 off-line isolates. Escherichia and Enterobacter were the most frequently identified genera from either facility, regardless of treatment. Citrobacter, Klebsiella, Leclercia, Proteus, Salmonella, and Serratia were also recovered from both facilities. Other Enterobacteriaceae recovered from the in-line facility included Buttiauxella, Erwinia, Hafnia, Kluyvera, Morganella, Providencia, and Yersinia. Only Enterobacteriaceae genera were identified from off-line eggs though related species were recovered from the in-line facility (Aeromonaceae and Pseudomonas cepacia). Differences in Aeromonaceae (Aeromonas, Listonella, Vibrio) prevalence were observed by treatment: 31.8, 25.7, and 47.1% for HH, HC, and CC, respectively. Higher proportions of Salmonella were presumptively identified from HC (36.5%) and CC (20.0%) than from HH washed eggs (5.0%). The 3-5 C reduction in shell surface tempera resulting from using cooler wash water temperatures may not be worth the observed decrease in microbiological quality.