Welcome to the Food Borne Disease Site. The sources of the foodborne illness pathogens are ubiquitous. Food and food products will always be contaminated with low levels of pathogens. At low levels, pathogenic microorganisms cause no problems. At illness thresholds, however, they can make people ill and cause death.

Saturday, February 03, 2007

What is Salmonella?

What is Salmonella?
The genus Salmonella is a member of the family Enterobacteriaceae, It is composed of bacteria related to each other both phenotypically and genotypically. Salmonella DNA base composition is 50-52 mol% G+C, similar to that of Escherichia, Shigella, and Citrobacter.

The bacteria of the genus Salmonella are also related to each other by DNA sequence. The genera with DNA most closely related to Salmonella are Escherichia, Shigella, and Citrobacter. Similar relationships were found by numerical taxonomy and 16S ssRNA analysis.

Salmonella nomenclature has been controversial since the original taxonomy of the genus was not based on DNA relatedness; rather names were given according to clinical considerations, e.g., Salmonella typhi, Salmonella cholerae-suis, Salmonella abortus-ovis, and so on. When serological analysis was adopted into the Kauffmann-White scheme in 1946, a Salmonella species was defined as "a group of related fermentation phage-type" with the result that each Salmonella serovar was considered as a species.

Since the host-specificity suggested by some of these earlier names does not exist (e.g., S. typhi-murium, S. cholerae-suis are in fact ubiquitous), names derived from the geographical origin of the first isolated strain of the newly discovered serovars were next chosen, e.g., S. london, S. panama, S. stanleyville.

Subsequently it was found that all Salmonella serovars form a single DNA hybridization group, i.e., a single species composed of seven subspecies, and the nomenclature had to be adapted. To avoid confusion with the familiar names of serovars, the species name Salmonella enterica was proposed with the following names for the subspecies: enterica I salamae II arizonae IIIa diarizonae IIIb houtenae IV bongori V indica VI Each subspecies contains various serovars defined by a characteristic antigenic formula.

Since this formal Latin nomenclature may not be clearly understood by physicians and epidemiologists, who are the most familiar with the names given to the most common serovars, the common serovars names are kept for subspecies I strains, which represent more than 99.5% of the Salmonella strains isolated from humans and other warm-blooded animals. The vernacular terminology seems preferred in medical practice, e.g., Salmonella ser. Typhimurium (not italicized) or shorter Salmonella (or S.) Typhimurium.
What is Salmonella?
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