This experiment was conducted to st

This experiment was conducted to study the prevalence of Salmonella and Escherichia coli (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. coli isolates
were isolated from the egg shell surface. Ten E. coli 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. coli
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. coli isolates isolated from egg shell surfaces. All the E. coli isolates
were negative for STb and cvaC genes. These data provide useful information regarding the prevalence of
virulent E. coli 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 coli. 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 4 °C, as compared with room temperature
which highlights the importance of storage of eggs at refrigerated temperatures.