Illness is associated with eating contaminated food products, predominantly poultry and eggs. There have, however, been famous outbreaks of food poisoning associated with unusual foods such as S napoli in chocolate, S typhimurium 124 in pepperami and S goldcoast in cheese. The incidence of salmonellosis is seasonal, peaking in late summer. The pathogenic mechanism involves the bacteria entering into enterocytes. Neutrophil infiltration of the mucosa occurs, the release of local and systemic inflammatory mediators promoting fluid secretion into the gut.
Illness is characterised by diarrhoea, vomiting and fever.
The diarrhoea usually settles within ten days. Occasionally the bacteria may invade the bloodstream, causing gram-negative septicaemia which carries with it a significant mortality. In the early 1980s, E coli O157 emerged as an important cause of food-borne disease. Unlike Campylobacter and Salmonella, E coli O157 does not invade the gut mucosa. It produces a toxin that acts on enterocytes and on the vascular endothelium.