What is O antigen in Salmonella?

O-antigens are glycopolymers in lipopolysaccharides expressed on the cell surface of Gram-negative bacteria. Variability in the O-antigen structure constitutes the basis for the establishment of the serotyping schema.

What is the O antigen in bacteria?

The O antigen is an extremely variable surface polysaccharide of Gram-negative bacteria. This variation is thought to allow the various clones of a species each to present a surface that offers a selective advantage in the niche occupied by that clone.

What is the meaning of somatic antigen?

so·mat·ic an·ti·gen. an antigen located in the cell wall of a bacterium in contrast to one in the flagella (flagellar antigen) or in a capsule (capsular antigen).

Where is O antigen in bacteria?

outer membrane
The O antigen, consisting of many repeats of an oligosaccharide unit, is part of the lipopolysaccharide (LPS) in the outer membrane of Gram-negative bacteria.

Why somatic antigen is called O antigen?

The O antigen, also called somatic antigen, is the polysaccharide portion of the outer membrane liposaccharide and the H antigen, also called flagellar antigen, is the protein flagellin that makes the filaments of the bacterial flagellum.

What is O antigen of Enterobacteriaceae?

Enterobacter cloacae is a well-characterized opportunistic pathogen that is closely associated with various nosocomial infections. The O-antigen, which is one of the most variable constituents on the cell surface, has been used widely and traditionally for serological classification of many gram-negative bacteria.

How many O antigens are there?

Of the 187 formally defined O antigens, six (O31, O47, O67, O72, O94 and O122) have since been removed and three (O34, O89 and O144) strains do not produce any O antigen.

What is O antigen made of?

The O-antigen or O-side chain is attached to the core polysaccharide and extends from the core out into the environment. It consists of repeating oligosaccharide subunits made up of three to five sugars. The individual chains can vary in length ranging up to 40 repeat units.

What do the O and H antigens tell us about Salmonella?

The O antigens are distinguished by their different chemical make-up. The H antigens are distinguished by the protein content of the flagella. Each O and H antigen has a unique code number. Scientists determine the serotype based on the distinct combination of O and H antigens.

What is a virus 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 surface antigens, allowing the epidemiologic classification of organisms to the subspecies level.

What is Salmonella typhi O and H?

S typhi O positive means active infection of typhoid fever. Active infection indicates the patient has an infection of Salmonella enterica serovar typhi. S typhi H positive means there is a past infection or it shows the result of the immunized person’s serum test report.

Is there an O antigen?

O-Antigens (also known as O-specific polysaccharides or O-side chains) are major component of the surface lipopolysaccharide (LPS) of Gram-negative bacteria and are highly variable in structure.

What are the somatic antigens of Salmonella?

The somatic (O) antigens, which are present on the outer membrane, are part of lipopolysaccharides (LPS) moieties. The heat-stable somatic antigens of Salmonella include both specific determinants and/or nondiscriminatory antigens.

What are the O and H antigens of Salmonella?

These antigens which are found on the cell surface of Salmonella are known as O and H antigens. The O antigen (also known as somatic antigen) is found on the cell wall of the bacteria, whereas the H antigen is produced in the flagellated portion.

Is there a modified method for the identification of Salmonella antigens?

This report describes two modified methods for the identification of Salmonella somatic (O) and flagellar (H) antigens. Over a period of 2 years, both modified methods were found to be approximately three times less labor intensive than the standard methods while requiring no more technical skill.

What is the history of Salmonella infection?

The first strain of Salmonella typhi was isolated from a patient in Vietnam. Patients affected by typhoid fever produce antibodies against the antigens of Salmonella bacteria. These antigens which are found on the cell surface of Salmonella are known as O and H antigens.

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