Shell quality effect on Salmonella Enteritidis (SE) and Escherichia coli behavior on chicken eggs surface submitted to an oscillating temperature regime and the risk of bacteria penetration in the content.

The objectives of this work were to demonstrate the behaviour of Salmonella Enteritidis and Escherichia coli on eggshell surface when they are submitted to temperature oscillation and to investigate the risk of bacteria penetration in chicken eggs submitted to this temperature condition. Eggs were separated in two blocks (no shell defects and little shell defects) by ovoscopy. The eggshell defects don't declassify eggs to consumer use. The shell surfaces had been contaminated with chicken faeces previously inoculated with SE and E. coli, on their meridional side (about 1/8 of their total area). They had been submitted to an oscillation temperature regime (8oC – zero up to 48 hours; 30oC – 49 up to 72 hours and 8oC – 73 up to 336 hours). Bacterial counts were performed at defined times. The shells were submitted to a surface washing with buffered peptone water, albumen and yolk were analyzed by decimal dilution. Five samples were analyzed per time and per shell and plated in agar MacConkey. The Exact Fischer's Test was used to show statistical differences between shell conditions, survival of bacteria on shell surface and their penetration in the egg contents.SE and E. coli had remained viable and maintained their counts on shell surface until the end of experiment (336 hours) in all samples, no shell defects and shell defects. The penetration in the content occurred only in eggs with shell defects during the 48 hours storage at 30oC. In these conditions, SE and E. coli can survive in shell surface and may allow the egg content contamination by the consumer use. When egg shell presented defects, the albumen and yolk contamination probability rised although no statistical significance was observed.