A tech is using the H (flagellar) antigen to serotype a suspected Salmonella species. The results of the serotyping are agglutination with one well that indicates a group of possible serotypes, not one particular serotype. Quality control passed. Why did this occur

Some Salmonella H antigens can occur in multiple strains and serotypes

An antigen (Ag) is any molecule/structure such as, for example, a molecule present on the surface of a pathogenic microorganism, that can be bound by a specific antibody and/or B-cell receptor.  The Kauffmann–White classification scheme is a system that was adopted for use in 1934 in order to categorize different serotypes of the bacterial genus Salmonella, based on their somatic-surface antigens. The system is a practical (diagnostic) method based on the variation in the somatic (O) and flagellar (H) antigens present in the cell wall of Salmonella species. In this classification system, 'O' antigens are determined based on oligosaccharides which are associated with lipopolysaccharide, while the "H" antigens are distinguished by the protein content of the Salmonella flagella.  

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Cbecause it is the only one describing a habitat

Active site is where they touch.