serotyp

This article uses the term serotype (also spelled serotyp in some languages) to denote the antigenically distinct variation within a microbial species. A serotype is defined by its unique set of surface antigens that are recognized by the immune system, and serotyping groups isolates into types that differ in their antibody reactivity.

In bacteria, serotypes are typically determined by combinations of surface components such as somatic (O) antigens, flagellar (H) antigens, and, in some species, capsular (K) polysaccharide antigens. The classical approach relies on serological assays, including agglutination or precipitation with reference antisera. Modern methods increasingly supplement or replace these tests with molecular typing and genome-based predictions of serotype from known antigenic loci.

The terms serotype and serovar are often used interchangeably in bacteria, although some fields distinguish them by nuance. Full designations may appear as species name followed by serotype or serovar, for example, Salmonella enterica serovar Typhimurium.

Serotyping plays an important role in epidemiology, surveillance, and vaccine strategy. Different serotypes can vary in virulence, geographic distribution, and immune recognition, influencing outbreak tracking, transmission studies, and the scope of vaccination programs. For instance, certain pathogenic serotypes may be targeted by vaccines, while others may emerge under immune pressure or through genetic exchange.

Examples of well-known serotypes include Escherichia coli O157:H7, several Salmonella enterica serovars such as Typhimurium and Enteritidis, and numerous Streptococcus pneumoniae serotypes. A key limitation is that serotyping captures only antigenic variation and does not fully reflect genetic relatedness among isolates, which is better assessed by genomic typing.