General Microbiology

Precipitation Reaction This reaction takes place only when antigen is in soluble form. Such an antigen when comes in contact with specific antibody in a suitable medium results into formation of an insoluble complex which precipitates. This precipitate usually settles down at the bottom of the tube. If it fails to sediment and remains suspended as floccules the reaction is known as flocculation. Precipitation also requires optimal concentration of NaCl, suitable…

CROSS INFECTION AND STERLIZATION IN DENTISTRY Cross infection is defined as the transmission of infectious agents amongst patients and staff with in hospital environment. Routes of Infection  Two routes are important : transdermal  and respiratory.   In transdermal route microorganisms enter the tissues of the recipient by means of injection through intact skin or mucosa (usually due to an accident involving a sharp instrument) or via d…

Complement Fixation Test (CFT) This test is based upon two properties of the complement viz: a. Complent combines with all antigen-antibody complexes whether or not it is required for that reaction b. Complement is needed in immunolytic reaction. Test system It contains an antigen and a serum suspected to be having antibody to that antigen. The serum is heat treated prior to the test to destroy its complement. Complement Is added in measured quantity to…

PHAGOCYTOSIS AND INTRACELLULAR KILLING A. Phagocytic cells 1. Neutrophiles/Polymorphonuclear cells PMNs are motile phagocytic cells that have lobed nuclei. They can be identified by their characteristic nucleus or by an antigen present on the cell surface called CD66. They contain two kinds of granules the contents of which are involved in the antimicrobial properties of these cells.  The second type of granule found in more mature PMNs is the secon…

Variant Forms of Bacteria Prortoplast ; surface is completely devoid of cell wall component, Spheroplast : Some residual cell wall component is present  Autoplast: protoplasts which are produced by the action of organisms’ own autolytic enzymes. L Form: replicate as pleomorphic filtrable elements with defective or no cell wall These are designated as L forms after the Lister Institute where these were discovered by Klineberger-Nobel. B…