Immunofluorescence
Written by Dr.ChrisImmunofluorescence: Fluorescence is the property of absorbing light rays of one wave length and emitting rays with different wave length. Serological reactions employing tagged antisera are used to detect minute amounts of weakly active antigen or antibodies. The method is suitable for only qualitative reactions. The fluorescent antibody technique is used for:
(1) Rapid serological diagnosis of […]
Tags: bacterial cell, Mycoplasma, phospholipid, protoplast, tricarboxylic acid cycle
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Opsonization
Written by Dr.ChrisOpsonization: This is another serological reaction which sensitizes bacteria for phagocytosis. The substances in serum which promote phagocytosis are called opsonins
The opsonic index is defined as ratio of phagocytic activity of patient’s blood having bacterium, to the phagocytic activity of blood from normal individual. It is measured by incubating fresh citrated blood with bacterial suspensions […]
Tags: opsonic index, phagocytic activity, phagocytosis
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Neutralization Test
Written by Dr.ChrisNeutralization Test: Specific antibodies are able to neutralise the biological effects of viruses, toxins and enzymes.
(a) Virus neutralization: Viruses when mixed with immune serum they loose their capacity to infect fresh host e.g., vaccinia, influenza and poliomyelitis. Neutralization may be quantitated on:
(i) Chorio allantoic membrane of chick embryo (pocks formation).
(ii) By enumeration of plaques on monolayer tissue […]
Tags: hemolytic activity, pocks formation, Toxin neutralization, Virus neutralization
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COOMB’S TEST: DETECT ANTIBODIES
Written by Dr.ChrisCoomb’s test: It is used for the detection of incomplete antibodies (non agglutinating anti Rh antibody), brucella, shigella and salmonella antigen.
Sera containing incomplete anti Rh antibodies is mixed with Rh positive red cells. Antibody globulin coats the surface of erythrocytes. Such erythrocytes coated with antibody globulin are washed free of all unattached proteins and treated […]
Tags: Parasitic diseases, Rickettsial diseases, Spirochaetal disease, Viral diseases
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AGGLUTINATION REACTIONS
Written by Dr.ChrisAGGLUTINATION REACTIONS: When a particulate antigen is mixed with its antibody in presence of electrolytes at a suitable temperature and pH, then the particles are clumped or agglutinated. It is more sensitive than precipitation for the detection of antibodies.
Uses
(1) Identification of bacteria e.g., serotyping of salmonella and shigella with known antisera.
(2) Serological diagnosis of infection e.g., Widal […]
Tags: Flagellar antigen, Hemagglutination, Macroagglutination, Microagglutination
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Types of Gel Diffusion
Written by Dr.ChrisGel diffusion are:
(1) Single diffusion in one dimension: The antibody is incorporated in agar gel in a test tube and antigen solution is layered over it The antigen diffuses downwards through the agar gel forming line of precipitation that appears to move downwards. Number of bands indicate number of different antigens present.
(2) Double diffusion in one dimension: […]
Tags: Double diffusion, immunoelectrophoresis, Radioimmuno electrophoresis, Single diffusion
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Techniques of Precipitation Reaction
Written by Dr.ChrisTechniques of Precipitation Reaction:
(1) Ring test: The test is very simple for detection of antigen. The antigen is layered over serum in a narrow tube. The reaction is visible as a white zone at the junction of two clear fluid. Examples are C-reactive protein test, Ascoli test, grouping of streptococci by Lancefield technique.
(2) Slide test: When a […]
Tags: B. subtilus, friable, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus hemolyticus
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PRECIPITATION: Antigen and Antibody Reaction
Written by Dr.ChrisPRECIPITATION: When a soluble antigen combines with its antibody in presence of electrolytes (NaC1) at a suitable temperature and pH the antigen antibody complex forms insoluble precipitate.
Uses of Precipitation Reaction
(1) Identification of bacteria e.g., detection of group specific polysaccharides substance in streptococci in Lancefield grouping etc.
(2) Identification of antigenic component of bacteria in infected animal tissue. e.g., […]
Tags: bacillus, clostridium, deamination, spores, sporosarcina, tryptophan
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Antigen and Antibody Reaction
Written by Dr.ChrisAntigen and Antibody Reaction: Antigen-antibody reactions are useful in laboratory diagnosis of various diseases, and in the identification of infectious agents in epidemiological survey. Antigen antibody reactions in vitro are called serological reactions.
Features of Antigen Antibody Reactions
(1) The reaction is highly specific.
(2) Entire molecules react and not fragment.
(3) There is no denaturation of antigen or antibody during reactions.
(4) Combination […]
Tags: bacterial cell, Mycoplasma, phospholipid, protoplast, tricarboxylic acid cycle
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METHODS FOR IDENTIFICATION OF ORGANISMS
Written by Dr.ChrisDEVELOPMENT OF RAPID METHODS FOR IDENTIFICATION OF ORGANISMS: The last few years have seen exciting advances in finding out new ways of identifying micro-organisms within a few minutes of arrival of a specimen in the laboratory. Specific microbial components may be detected by countercurrent immunoelectrophoresis also designated as CIE. Another nice method for identifications of […]
Tags: bacillus, clostridium, deamination, spores, sporosarcina, tryptophan
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Analysis of Bacteria
Written by Dr.ChrisAnalysis of Bacteria: Antigenic analysis: By using specific sera we can identify organism by agglutination reaction e.g., beta hemolytic streptococci is differentiated into 18 serological groups (A to T except I and J) on the bases of polysaccharides component. Likewise pneumococcus is divisible into 77 capsular types by capsular swelling reactions with antititaysular sera.
Bacteriophage typing: […]
Tags: Alcaligens fecalis, Escherichia coli, Gram negative bacilli, proteus, pseudomonas, salmonella, Vibrio cholerae
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Types of Testing Bacteria
Written by Dr.ChrisTypes of Testing Bacteria: The more important and widely used tests are as under:
1. Sugar fermentation: This is tested in sugar media having Andrade’s indicator. Acid production changes the color of medium into pink. Gas produced collects in Durham’s tube.
2. Indole production: This test demonstrates production of indole from tryptophane. This tryptophane is present in peptone water. […]
Tags: B. subtilus, friable, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus hemolyticus
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Staining Reaction
Written by Dr.ChrisStaining Reaction: Simple stain brings out morphology best. Differential and special stain are necessary to bring out characteristics like flagella, capsule, spores and metachromatic granules.
In Gram stained smears we note shape, size, arrangement, spores and so on. Gram stain divides bacteria into Gram positive and Gram negative bacilli, Ziehl Neelsen stain into acid fast and […]
Tags: Alcaligens fecalis, Escherichia coli, Gram negative bacilli, proteus, pseudomonas, salmonella, Vibrio cholerae
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Identification of Bacteria
Written by Dr.ChrisIdentification of Bacteria: For the identification of organism we proceed as under.
(1) Microscopic examination: It helps to find out whether the bacteria is cocci, bacilli, vibrio, spirillum or spirochaete. On Gram staining we can have two groups of organism; Gram positive and Gram negative organisms.
(2) Motility: Pathogenic cocci are non motile. Among Gram negative bacilli, salmonella, Escherichia […]
Tags: Alcaligens fecalis, Escherichia coli, Gram negative bacilli, proteus, pseudomonas, salmonella, Vibrio cholerae
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METHODS OF ANAEROBIC CULTURE
Written by Dr.ChrisMETHODS OF ANAEROBIC CULTURE: Obligate anerobes grow only in absence of free oxygen. These bacteria lack mechanism of oxidation through respiratory enzymes like cytochrome oxidase, catalase and peroxidase resulting in H202 accumulation. This H2O, is toxic for the growth of anaerobic bacteria.
Clostridium tetani are strictly anaerobic. A number of methods are described for achieving anaerobiosis […]
Tags: B. subtilus, friable, Mycobacterium tuberculosis, Pseudomonas aeruginosa, Streptococcus hemolyticus
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