serovars

A serovar, or serotype, is a distinct variation within a species defined by differences in surface antigens that are recognized by host antibodies. In bacteria, the principal determinants are somatic O antigens and flagellar H antigens, with capsule-associated K antigens in some species. Serovars reflect shared antigenic properties and are used for practical classification rather than as a formal taxonomic rank.

Serotyping is commonly done with serological methods, such as slide agglutination using antisera against specific O and H antigens. Classic schemes, like the Kauffmann-White scheme for Salmonella, provide standardized serovar names. Modern practice also employs molecular methods and whole-genome sequencing to infer antigenic profiles, trace lineages, and complement traditional serotyping when antigen expression is variable or unknown.

In public health and epidemiology, serovars facilitate outbreak detection, surveillance, and source attribution. For example, Salmonella enterica serovars Typhimurium and Enteritidis are frequent causes of human foodborne illness, while Salmonella Typhi is associated with typhoid fever. Escherichia coli serovar O157:H7 is well known for severe gastrointestinal disease, and Listeria monocytogenes serovars such as 1/2a, 1/2b, and 4b are linked to human cases. Across species, the number and identity of serovars can vary, and serovar designations may be updated as new antigenic types emerge.

Overall, serovars provide a practical framework for describing antigenic diversity within microbial populations and for guiding diagnostics, treatment considerations, and epidemiological investigations.