Serotype

A serotype or serovar is a distinct variation within a species of bacteria or virus or among immune cells of different individuals.

These microorganisms, viruses, or cells are classified together based on their shared reactivity between their surface antigens and a particular antiserum, allowing the classification of organisms to a level below the species.

[clarification needed] Serotyping often plays an essential role in determining species and subspecies.

[citation needed] Serotypes were discovered in hemolytic streptococci by the American microbiologist Rebecca Lancefield in 1933.

[5] For organisms with many possible serotypes, first obtaining a polyvalent match can reduce the number of tests required.

A number of bacteria species, including Streptococcus pneumoniae, display the Quellung reaction visible under a microscope.

However, their results may not always agree with traditional serotyping, as they can fail to account for factors that affect the expression of antigen-determining genes.

In some situations, this effect can be reduced by serotyping both recipient and potential donors to determine the closest HLA match.

The process to identify the serovar of the bacterium consists of finding the formula of surface antigens which represent the variations of the bacteria.

The Wzy pathway is used by almost all gram-positive bacteria, by lactococci and streptococci (exopolysacchide), and is also responsible for group 1 and 4 Gram-negative capsules.