Serotype

2a and 2b on surface, which are recognized by two distinct antibodies, 3a and 3b, respectively 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. A group of serovars with common antigens is called a serogroup or sometimes serocomplex. Serotyping often plays an essential role in determining species and subspecies. The Salmonella genus of bacteria, for example, has been determined to have over 2600 serotypes. Vibrio cholerae, the species of bacteria that causes cholera, has over 200 serotypes, based on cell antigens. Only two of them have been observed to produce the potent enterotoxin that results in cholera: O1 and O139. Serotypes were discovered in hemolytic streptococci by the American microbiologist Rebecca Lancefield in 1933.

2a and 2b on surface, which are recognized by two distinct antibodies, 3a and 3b, respectively]] 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. A group of serovars with common antigens is called a serogroup or sometimes serocomplex. Serotyping often plays an essential role in determining species and subspecies. The Salmonella genus of bacteria, for example, has been determined to have over 2600 serotypes. Vibrio cholerae, the species of bacteria that causes cholera, has over 200 serotypes, based on cell antigens. Only two of them have been observed to produce the potent enterotoxin that results in cholera: O1 and O139. Serotypes were discovered in hemolytic streptococci by the American microbiologist Rebecca Lancefield in 1933. ==Role in organ transplantation== positive red blood cells with anti-A3 alloreactive antisera containing Anti-A3 IgM]] The immune system is capable of discerning a cell as being 'self' or 'non-self' according to that cell's serotype. In humans, that serotype is largely determined by human leukocyte antigen (HLA), the human version of the major histocompatibility complex. Cells determined to be non-self are usually recognized by the immune system as foreign, causing an immune response, such as hemagglutination. Serotypes differ widely between individuals; therefore, if cells from one human (or animal) are introduced into another random human, those cells are often determined to be non-self because they do not match the self-serotype. For this reason, transplants between genetically non-identical humans often induce a problematic immune response in the recipient, leading to transplant rejection. In some situations, this effect can be reduced by serotyping both recipient and potential donors to determine the closest HLA match. ===Human leukocyte antigens=== ===Shigella=== Shigella are only classified by their O antigen, as they are non-motile and produce no flagella. Across the four "species", there are 15 + 11 + 20 + 2 = 48 serotypes. Some of these O antigens have equivalents in E. coli, which also cladistically include Shigella. ===Streptococcus=== Streptococcus pneumoniae has 93 capsular serotypes. 91 of these serotypes use the Wzy enzyme pathway. 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. ===Human papillomavirus=== According to a study published in 2024¹ carried out on a sample of 63 women affected by human papillomavirus, the serotypes HPV 6, HPV 82 and HPV 89 appear to be those at low risk (1.5% for each), while the HPV 81 serotype is the one most often encountered in subjects affected by a single infection (40.9%). Among subjects experiencing multiple infections, HPV 16 serotype tops the list with 28.8%. ===SARS-CoV-2=== Within a few years since its appearance, SARS-CoV-2 has diversified into different serotypes. All variants before Omicron belong to the single serotype I (gamma). Then come those designated as serotypes II (BA.1), III (BA.2), IV (BA.5), V (XBB), and VI (BA.2.86).

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