Food borne pathogens and commercial eggs in Australia

A low level of bacterial contamination on an eggshell is important from both food safety and storage perspectives. A high number of bacteria present on the eggshell surface increases the chances of eggshell penetration and contamination of internal contents. Overall, food quality and sanitary processing conditions can be judged by Enterobacteriaceae populations. In chapter 2, no significant differences were detected in the Enterobacteriaceae counts of the eggshell surface or in the eggshell pores, of visibly clean eggs collected from Australian layer flocks at various stages of lay. Out of all eggs tested, 4.51% (14/310) eggshell samples were reported Salmonella positive. The rate at which Salmonella infected flocks produce Salmonella contaminated eggs is unclear. In chapter 3, the possible transmission of Salmonella from the environment to the egg was investigated with the help of longitudinal studies on commercial egg farms. Results indicated that the odds of an eggshell being positive for Salmonella were 91.76, 61.5 and 18.2 times higher when faecal, egg belt and dust samples, respectively, tested positive for Salmonella. On other hand, a one log increase in the load of Salmonella detected in faecal, egg belt and in the floor dust samples, respectively, resulted in 35%, 43% and 45% increase (p<0.001) in the odds of an eggshell testing positive for Salmonella. In chapter 4, the shedding of Salmonella in a single age commercial egg layer flock was also investigated at the onset of lay (18 weeks) followed by two longitudinal samplings at 24 and 30 weeks. At the age of 18 weeks, when the first sampling was performed, the prevalence of Salmonella in faeces was 82.14%. However, in later samplings, at the age of 24 and 30 weeks, the prevalence of Salmonella in faeces was significantly reduced (p