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Prevalence of Coliforms, Salmonella, Listeria and Campylobacter in Eggs and the Environment of Conventional Cage and Free-Range Egg Production

29 June 2012, at 12:00am

Researchers based in the US found some differences in the prevalence of coliforms, Salmonella, Listeria and Campylobacter on and within eggs and in the environment of a sister flock of conventional cage and free–range laying hens. Significantly more Campylobacter–positive swabs were obtained from the free–range nest boxes than from free–range grass and conventional cages. There was no evidence that the free-range system offered any benefits over battery cages in terms of the prevalence of foodborne pathogens.

There is a desire by US consumers for eggs produced by hens in alternative production systems, according to a recent paper in Poultry Science. Deana Jones of the USDA Agricultural Research Service in Athens, Georgia and co-authors there and at North Carolina State University report that, as the retail shell–egg market offers these products to accommodate consumer demands, additional information is needed to ensure processing methodologies result in safe eggs from all egg sources.

They conducted a study to determine whether there were differences in the prevalence of coliforms, Salmonella, Listeria and Campylobacter on and within eggs and in the environment of a sister flock of conventional cage and free–range laying hens. Microbial sampling occurred approximately every six weeks between 20 and 79 weeks of age.

A random sampling of typical coliform colonies produced 371 viable isolates for biochemical identification. Twenty-nine genera or species of bacteria were identified.

There was a significantly greater (P<0.0001) prevalence of Campylobacter in the free–range nest box swabs than in the free–range grass and conventional cage swab samples; the numbers of positives were eight for the nest box, one for grass and zero for the cage.

Seven isolates of Listeria innocua were detected with no significant difference in prevalence between the treatments. Isolates were associated with eggshells (two for the free–range floor; one for the cage) and the free-range environment (two for the nest box; two for the grass).

There were 21 Salmonella isolates detected between all sample locations, with no significant difference in the prevalence of Salmonella detection between the treatments.

Jones and co-authors concluded that additional studies are needed to understand fully the effect of alternative production methods on the prevalence of pathogens and coliforms associated with nest–run eggs and the production environment.

Reference

Jones D.R., K.E. Anderson and J.Y. Guard. 2012. Prevalence of coliforms, Salmonella, Listeria, and Campylobacter associated with eggs and the environment of conventional cage and free-range egg production. Poult. Sci., 91(5):1195-1202. doi: 10.3382/ps.2011-01795

Further Reading

You can view the full report by clicking here.


June 2012