Identification of Enterobacteriaceae from washed and unwashed commercial shell eggs.

摘要

In order to evaluate the effect of processing on the safety and quality of retail shell eggs, the incidence of Enterobacteriaceae on commercially washed and unwashed eggs was investigated. Results demonstrated that commercial processing decreased microbial contamination of egg shells. To determine which species persisted during storage on washed or unwashed eggs, Enterobacteriaceae isolates were selected and identified biochemically. For each of 3 replications, eggs were purchased from a commercial processing plant, transported back to the laboratory, and stored at 4degC. Once a wk for 6 wk, 12 eggs for each treatment (washed and unwashed control) were rinsed in sterile phosphate-buffered saline. A 1-ml aliquot of each sample was plated onto violet red bile glucose agar with overlay and incubated at 37degC for 24 h. Following incubation, plates were observed for colonies characteristic of the family Enterobacteriaceae. A max. of 10 isolates per positive sample were streaked for isolation before being identified to the genus or species level using commercially available biochemical strips. Although most of the isolates from the unwashed control eggs belonged to the genera Escherichia or Enterobacter, many other genera and species were identified. These included Citrobacter, Klebsiella, Kluyvera, Pantoea, Providencia, Rahnella, Salmonella, Serratia and Yersinia. Non-Enterobacteriaceae also recovered from the unwashed egg samples included Xanthomonas and Flavimonas. Very few washed egg samples were contaminated with any of these bacteria. These data provide useful information on the effectiveness of processing in removing microorganisms from commercial shell eggs.