The organism that causes salmonella is a genus of bacteria of the family Enterobacteriaceae, members of which are commonly found in the intestinal tract of humans and other animals. It is named after D.E. Salmon, the American bacteriologist who described it in 1885. Salmonellae are important in causing food-borne and WATER-BORNE DISEASE.
The salmonellae can be divided into 3 groups based on host preference. Those primarily adapted to humans include the typhoid and paratyphoid organisms, which, compared to salmonella in other groups, have long incubation periods (10-21 days), cause high fever, invade the bloodstream, require a slow convalescence, and have a higher proportion of carriers (ie, asymptomatic victims who excrete the organism). All serotypes belong to a single species, S. enterica, and types such as S. typhirium have no taxonomic status. Those primarily adapted to animal hosts include S. choleraesuis (pigs), S. dublin (cattle) and S. pullorum and S. gallinarum (chickens).
Only the first 2 serotypes are significant for human illness. Salmonellae not adapted to any specific host include the more than 2000 serotypes with the potential for causing human salmonellosis, a form of gastroenteritis. S. typhimurium is the serotype causing most salmonellosis in Canada and other countries. Diarrhea, abdominal cramps, fever, nausea and vomiting occur 8-48 hours after consumption of less than 10 organisms. Patients typically recover after a few days, but infants and elderly persons can become seriously ill and occasionally may die. Although salmonellae are mainly transmitted to humans through food, they can also cause illness through contact with infected humans and pets and through drinking contaminated water.
An estimated 627 200 cases of food-borne salmonellosis probably cost Canadians as much as $1 billion annually in total medical care, time away from work and economic loss to food companies and restaurants supplying the contaminated foods. In Canada, as in other countries, salmonella remains the most extensive and expensive cause of food-borne disease. Increased foreign trade and travel have brought in serotypes from other countries and the increased demand for highly processed animal products and interprovincial distribution have made salmonellae widespread in the Canadian environment (eg, about 50% of poultry carcasses contain the organism). Foods associated with salmonellosis in Canada have been turkeys, chickens, unpasteurized milk, beef, pork, salami, products made with cracked eggs, cheddar cheese, bean sprouts, salads, chocolate candy, pepper and cream pies.
Salmonellae are difficult to eliminate from the environment and, once they come in contact with suitable food, can multiply rapidly at room temperature. Prevention of illness depends on decreasing the source of the organism (eg, salmonellae-free animal feed), having better hygienic conditions in slaughterhouses and processing plants, reducing the chances of cross-contamination in the food service or home kitchen, and not allowing growth to take place by keeping the food either cold (4C or less) or hot (60C or more). Government and industry are initiating a Hazard Analysis Critical Control Point approach from farm to consumer (gate to plate) to reduce the levels of pathogens throughout the food chain. Terminal treatment of the final products, however, through food irradiation or thorough cooking is the only way to eliminate pathogens.