Fundamental Food Microbiology, Third Edition - Fuad Fathir

FOODBORNE INFECTIONS 363
stand the importance of these factors in the increase of salmonellosis and to develop
corrective measures to control the incidence.
There are more than 2000 serovars (based on somatic, flagellar, and capsular
antigen types) of Salmonella, potentially capable of causing salmonellosis in
humans. Along with fecal–oral direct transmission, contaminated food and water
can cause salmonellosis. Recently, a better system of nomenclature has been developed
to group these serovars in a few species instead of considering each as a separate
species.
1. Current Nomenclature System
The serovars of Salmonella have a high degree of relatedness in their DNAs. It was
proposed on this basis that the genus Salmonella should have only one species,
Salmonella enterica, and six subspecies, two of which are from the Arizona group
(Table 25.1). The specific epithets that were used before (e.g., typhimurium for Sal.
typhimurium) should be considered as the serotypic name, and the strains of a
serotype can be distinguished by numerals, letters, and a combination, as previously
used. It is recommended that in formal publications, the complete name of the species
and subspecies be given (e.g., Salmonella enterica subsp. enterica). Then serotypic
names can be used (e.g., ser Typhimurium; not italicized). In informal communications,
cultures may be reported in familiar terms (e.g., Salmonella Typhimurium). 4
In this chapter, the previous method has been replaced for most serovars (e.g.,
Salmonella Typhimurium). The two serotypes associated with frequent incidents of
foodborne illness of Salmonella, Sal. Typhimurium, and Sal. Enteritidis, are in
Subspecies 1.
2. Predominant Serotypes in Salmonellosis
Among the six subspecies Salmonella enterica, subsp. enterica includes most serotypes
frequently associated with foodborne salmonellosis. However, two of the more
than 2000 serotypes, serotype Typhimurium and serotype Enteritidis, are involved
in higher frequencies worldwide. Many animals, including food animals and pets,
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Table 25.1 Six Subspecies of Genus Salmonella
1. Salmonella enterica subsp. a enterica
2. Salmonella enterica subsp. salamae
3a. Salmonella enterica subsp. arizonae
3b. Salmonella enterica subsp. diarizonae
4. Salmonella enterica subsp. houtenae
5. Salmonella enterica subsp. bongori
a The relationship between this subspecies scheme and
Kauffman's subgenus scheme are as follows: Subspecies 1
corresponds to Subgenus I, Subspecies 2 corresponds to
Subgenus II, Subspecies 3a and 3b correspond to Subgenus
III and Arizona hinshawii, Subspecies 4 corresponds to
Subgenus IV, and Subspecies 5 constitutes six atypical
serotypes from Subgenus II and IV.