Recovery of Salmonella and Escherichia coli from commercial egg shells and effect of translucency on bacterial penetration in eggs

Kapil Chousalkar, P. Flynn, M. Sutherland, Jason Roberts, B.F. Cheetham

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40 Citations (Scopus)


This experiment was conducted to study the prevalence of Salmonella and Escherichia coil (E. coli), from the surface of egg shells, egg shell membranes or pores, and internal contents from unwashed eggs collected from commercial caged layer farms in Australia. Egg shell swabs, shell crush and egg internal contents (yolk and albumen) of an individual egg were processed for bacteriological examination. Salmonella spp. were not detected from any of the egg shell surfaces, egg shell crush or egg internal contents. Thirty five E. colt isolates were isolated from the egg shell surface. Ten E. coil strains were also isolated from shell crush. However, the internal contents of eggs appeared to be sterile. Polymerase chain reaction was performed on forty-five E. coil isolates using primers for heat stable enterotoxin genes A and B (STa and STb) and also for colicin V gene (cvaC). STa gene was detected in four E. coil isolates isolated from egg shell surfaces. All the E. coil isolates were negative for STb and cvaC genes. These data provide useful information regarding the prevalence of virulent E. coil and Salmonella spp. on and in unwashed eggs collected from layer farms. These data also suggest that unwashed eggs collected from caged layer farms are unlikely to be sources of Salmonella outbreaks. Egg shell translucency could be due to changes in the mammillary layer and mamillary cores during the early phases of egg shell formation and has the potential to increase the incidence of microcracks in egg shells, and hence, may be responsible for bacterial penetration. There was a significant correlation between egg shell translucency and egg shell penetration by Salmonella Infantis and E coil. Both strains of bacteria were able to penetrate the translucent egg shells even at very low doses. The penetration, however, was hindered in both translucent and non translucent eggs at 4degrees C, as compared with room temperature which highlights the importance of storage of eggs at refrigerated temperatures
Original languageEnglish
Pages (from-to)207-213
Number of pages7
JournalInternational Journal of Food Microbiology
Issue number1-2
Publication statusPublished - Aug 2010

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