What is the O antigen in bacteria?
Abstract. 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 are the H and O antigens of E coli?
The O polysaccharide and flagellin are the two major antigens of gram-negative bacteria, also known respectivly as the O and H antigens. Both are highly polymorphic, and Escherichia coli, if one includes the Shigella strains, has 187 O and 53 H forms defined by serology (4, 6, 15, 21).
What is O antigen used for?
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.
Where is O antigen in bacteria?
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.
What is H and O in widal test?
Salmonella Infections The traditional Widal test measures antibodies against flagellar (H) and somatic (O) antigens of the causative organism. In acute infection, O antibody appears first, rising progressively, later falling and often disappearing within a few months.
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. Therefore, structures are presented for 176 of the 181 E.
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.
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.
Where is H antigen found?
RBCs
The Hh blood group contains one antigen, the H antigen, which is found on virtually all RBCs and is the building block for the production of the antigens within the ABO blood group.
What is the difference between 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.
What is meant by Salmonella typhi O?
Salmonella Typhi (S. Typhi) are bacteria that infect the intestinal tract and the blood. The disease is referred to as typhoid fever. S. Paratyphi bacteria cause a similar, but milder illness, which comes under the same title.
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 is the difference between O and H antigens?
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 the H antigen made of?
A slender threadlike structure, called the H antigen, that is part of the flagella. The O antigens are distinguished by their different chemical make-up. The H antigens are distinguished by the protein content of the flagella.
What are the properties of O antigens?
Somatic antigens are heat stable. Flagellar antigens are heat-labile. 6. 7. 8. Trichloro-acetic acid is used for extraction of O antigens. Since the property was first shown by Boivin, O antigen alternatively referred to as boivin antigen.
What is the difference between flagella and H antigen?
Flagella is the whole structure, while the slender threadlike portion of the flagella is called the H antigen. New technology is transforming how we detect and investigate outbreaks. Watch the video to learn more.