General Microbiology

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…

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…

Test for Antigen - Antibody Reactions Antigens are those substance that stimulates the production of antibodies which, when enter into the body it reacts specifically in a manner that are clearly visible.  Some antigens may not induce antibody production, but instead creates immunological tolerance.  An antigen introduced into the body produces only specific antibodies and will react with only those specific antigens.  These antibodies appear …

CHEMICAL AGENTS Chlorine and iodine are most useful disinfectant Iodine as a skin disinfectant and chlorine as a water disinfectant have given consistently magnificent results. Their activity is almost exclusively bactericidal and they are effective against sporulating organisms also.  Mixtures of various surface acting agents with iodine are known as iodophores and these are used for the sterilization of dairy products. Apart from chlorine, hypochlorite…

Measurement of Bacterial of Growth A convenient method is to determine turbidity by photoelectric colorimeter or spectrophotometer.  The cell number can be counted as total cell number as well as viable count. Viable Count Viable number of bacteria can be counted by inoculating the suspension onto solid growth medium and counting the number of colonies. Since each colony is the end product of one viable bacterium, their count gives the number of viable bact…