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O, H and Vi antigens
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Based on biochemical reactions,(Reeves, et.al., 1989), the genus Salmonella is divided into two species, S.enterica and S.bongori.
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S.enterica is subdivided into 6 subspecies. Enterica (I), Salamae (II), Arizonae (III a), Diarizonae (III b), Indica (IV) and Houtenae (V).
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Sub genus enterica is the largest and most important, containing all the species that commonly cause human and animal infections.
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Members of this sub genus are given a name like S.enterica sub sp. enterica serovar typhimurium.
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Serological classification is done by Kauffmann – white scheme. It depends on the identification by O and H antigens of the strain and agglutination
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Example
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O serogroup
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*
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Serotype
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Antigens
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O
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H
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Phase 1
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Phase II
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2
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A
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Paratyphi A
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1,2,12
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a
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-
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4
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B
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Paratyphi B
Typhimurium
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1,4,5,12
1,4,5,12
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b
c
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1,2
1,2
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7
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C
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Cholera suis
Paratyphi C
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6,7
6,7 (W)
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c
c
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1,5
1,5
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9
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D
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Typhi
Enteritidis
Pullorum and gallinarum
Dublin
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9 ,12 (W)
1,9,12
1,9,12
1,9,12 (Vi)
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d
g, m
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g, p
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1,7
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-
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Primary subdivision is into O serogroups, each of which shares a common somatic antigen.
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Where more than one O antigen is present, one of them is the major O Ag and is regarded as determining the group to which the strain shall be allocated.
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O serogroups were formerly designated by letters of the alphabet (A-Z).
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But now are indicated by numbers 1,2,3… The series of O antigens numbered O1 –67 is not continuous because some O antigens were originally assigned to bacteria that proved subsequently not to be salmonellae. Thus, only 46 O serogroups are defined by the 67 O antigens described.
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Participants