A serovar, also called a serotype, is a distinct variant within a species of bacteria or virus that is defined by the antigenic properties of its surface structures. These antigenic differences cause the organism to react uniquely with specific antisera, enabling classification into separate serological groups.
Explanation
Serological typing distinguishes microorganisms based on the specific set of antigens present on their cell surface, such as polysaccharides, lipopolysaccharides, flagellar proteins or capsular components. Organisms that share common antigenic determinants belong to the same serogroup, while those with distinct antigenic combinations are considered separate serovars. In Salmonella and Escherichia coli, for example, the O (somatic), H (flagellar) and sometimes K (capsular) antigens are used to assign serovars. Salmonella enterica has more than 2,500 serovars, including Typhi (causative agent of typhoid fever) and Typhimurium (a common cause of foodborne illness). Serotyping is crucial for public health surveillance, outbreak investigations and vaccine development because it allows epidemiologists to track the spread of specific strains and identify sources of infection. Viral serotypes, such as the four dengue virus serotypes, are distinguished by variations in viral envelope proteins that elicit different immune responses. While molecular typing methods are increasingly used, serovar designations remain a valuable tool for understanding the diversity and epidemiology of microbial species.
Examples and Significance
- Salmonella enterica serovar Typhi causes typhoid fever and is adapted to human hosts, whereas serovar Typhimurium infects a broad range of animals and causes gastroenteritis.
- Escherichia coli O157:H7 is a serovar defined by its O and H antigens and is associated with hemorrhagic colitis and hemolytic uremic syndrome.
- Vibrio cholerae O1 and O139 serovars are responsible for epidemic cholera; their distinct lipopolysaccharide antigens aid in identifying outbreak strains.
- Dengue virus has four serotypes (DENV‑1 to DENV‑4). Infection with one serotype confers immunity to that serotype but not to the others.
Serovar classification helps scientists and clinicians differentiate closely related strains, monitor disease spread and develop targeted diagnostics and vaccines.
Related Terms: Serotype, Antigen, Serogroup, Strain, Serotyping