Enterobacteriaceae and related organisms isolated from shell eggs collected during commercial processing

Area of Science:

• Food safety
• Microbiology
• Agricultural processing

Background:

• Commercial shell eggs undergo washing and grading in the US.
• Processing guidelines aim to maintain egg quality but their impact on safety is less understood.
• Enteric bacteria contamination in shell eggs is a public health concern.

Purpose of the Study:

• To identify enteric bacteria present in commercial shell egg processing plants.
• To determine if these bacteria persist throughout the commercial processing line.
• To evaluate the effectiveness of commercial washing procedures in reducing bacterial contamination.

Main Methods:

• Eggs were sampled from multiple sites along the processing line in three commercial plants.
• Rinse technique used to collect bacterial samples from egg surfaces.
• Enterobacteriaceae were detected and enumerated using violet red bile glucose agar.
• Isolated bacteria were identified to genus or species using biochemical tests.

Main Results:

• Various genera and species of Enterobacteriaceae and other bacteria were detected at different processing stages.
• Highest bacterial counts were found in pre-processing and dirty egg samples.
• Escherichia coli and Enterobacter spp. were consistently isolated across all plant visits.
• Bacterial recovery was significantly lower from fully processed eggs compared to unwashed eggs.

Conclusions:

• Commercial shell egg washing procedures effectively reduce bacterial contamination.
• The processing line, particularly washing, plays a crucial role in enhancing shell egg safety.
• Further research may focus on specific bacterial reduction efficacy at each processing step.