Impacts of Housing and Storage Environments on Physical Quality and the Potential Public Health Risks of Chicken Table Eggs

Abstract

The freshness and safety of table eggs are important features that affect consumers' choices. A total of 210 fresh and stored table eggs were sampled from nine-layer hen flocks raised in 6 cage houses and 3-deep-litter houses. Egg measurements of external and internal quality were performed on 60 eggs, while the microbiological examination was performed on 150 eggs (every 3 eggs were examined as a composite). Additional samples from floor litter, cage swabs, feces, and ovaries were collected for bacteriological isolation. Molecular detection of genes encoding virulence factors in Escherichia coli and Staphylococcus aureus isolates were performed by PCR. Results of egg quality measurements revealed significant reductions in specific gravity, albumin index, and Haugh unit of stored eggs when compared to fresh eggs (P < 0.05). Storing eggs either at > 25°C or within 20 -22°C led to the deterioration of egg quality parameters but didn't affect microbial load when compared with fresh eggs (P > 0.05). Deep litter housing environment significantly raised the counts of aerobic bacteria (R2 = 0.70, P = 0.003), and Staphylococcus spp. (R2 = 0.91, P < 0.0001) on eggshells. Virulence genes stx1, eae, hlyA, and stx2 of E. coli were detected in feces, ovaries, and on eggshells of composites collected from cage houses. While Staphylococcus aureus MecA was detected on eggshells and internal content of egg composites collected from deep litter houses. Obtained results revealed the critical role of storage temperature on egg quality parameters, as well as, the great influence of the housing environment on the microbial profile of produced eggs. Regular monitoring and corrective control measures should be set to maintain egg quality and safety at acceptable levels.