Kauffman-White classification

The Kauffman and White classification scheme is a classification system that permits serological varieties of the genus Salmonella to be differentiated from each other. This scheme differentiates isolates by determining which surface antigens are produced by the bacterium. First, the "O" antigen type is determined. "O" antigens are the polysaccharides associated with the lipopolysaccharide of the bacterial outer membrane. Having found the "O" antigen group, the "H" antigen is determined. The "H" antigens are proteins associated with the bacterial flagella (singular; flagellum). Salmonellas exist in two phases; a motile phase and a non-motile phase. These are also referred to as the specific and non-specific phases. Different "H" antigens are produced depending on the phase in which the salmonella is found. Non-motile isolates may be "switched" to the motile phase using a Cragie tube - bacteria are inoculated down the center of a hollow tube in a semi-solid nutrient agar. Those bacteria that become motile can then swim out of the bottom of the tube and are recovered from the agar outside of the tube. Pathogenic strains of Salmonella typhi carry an additional antigen, "Vi", so-called because of the enhanced virulence of strains that produce this antigen, which is associated with a bacterial capsule.

• Antigens in brackets are those that are rarely expressed in that serovar.

The cost of maintaining a full set of antisera precludes all but reference laboratories from performing a complete serological identification of salmonella isolates. Most laboratories stock only a limited range of antisera, and the choice of stock sera is largely determined by the nature of the specimens to be processed.

A common set of working antisera is shown below:

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Laboratories that are likely to investigate typhoid also carry antiserum raised against the Vi antigen.

A set of "Rapid Diagnostic Sera" is also held and is used for determination of common specific H-antigens except i-H. After obtaining a positive agglutination with the polyvalent-H specific and non-specific antiserum, the three RDS antisera are used to identify the H antigen present. Depending on the pattern of positive and negative reactions with the RDS antisera, the specific H antigen may be identified:

E = polyvalent for eh, enx, etc.
G = polyvalent for gm, gp, etc.
L = polyvalent for lv, lw, etc.