Salmonella in chicken meat, eggs and humans; Adelaide, South Australia, 2008

Abstract

Varieties of Salmonella enterica are the second most commonly notified causes of gastroenteritis in Australia. Outbreaks of Salmonella infection are commonly linked to food, particularly foods containing chicken meat and eggs. A number of European countries have introduced interventions based on Salmonella surveillance systems in the food industry and these have led to subsequent decreases in notification rates in humans. A descriptive case-series of human Salmonella infections notified in metropolitan Adelaide, South Australia, was conducted in 2008. Human Salmonella serotypes identified were then compared to serotypes identified from a retail chicken and egg survey conducted over the same time period in Adelaide. Ninety-four human cases of salmonellosis were included in the study. Thirty-one serotypes were identified and 61.7% of these were Salmonella enterica serovar Typhimurium (S. Typhimurium). In the week prior to illness, 62.8% of participants reported eating chicken and 47.9% reported eating eggs. Salmonella was identified in 38.8% of retail chicken samples; S. Infantis and S. Typhimurium phage type 135a were most commonly identified. No egg contents were found to contain Salmonella, but the pathogen was isolated on 3.5% of egg external surface samples. Eleven serotypes were common to both chicken and human samples, two serotypes were common to eggs and humans, and one serotype (S. Infantis) was common to all three sources. Serotypes of Salmonella isolated from chicken and egg samples included serotypes that were also isolated from humans, in cases included in this study, and in outbreaks previously investigated within Australia. Poultry meat and eggs are potential sources of introducing a defined range of human pathogens into South Australian kitchens. Ongoing systematic surveillance of animals and their food products, at farm and retail level for Salmonella could provide more definitive evidence of links between food sources and human infections; and also allow accurate measurement of interventions taken to reduce rates of Salmonella isolations in animal-based foods.