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nature of the work

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Nature of the work undertaken in the Microbiology Department The nature of the work undertaken in the Microbiology department includes the Grams Staining technique. It distinguish between Gram - positive and Gram - negative bacteria. It investigates the effectiveness of antiseptics and antibiotics in microbes by using the dilution plate technique and the ELISA technique. There are three techniques which is undertaken in the Microbiology department. 1- Gram Staining 2- The ELISA technique 3- And using the dilution plate technique 1- Gram Staining:- or Gram's method is an empirical method of differentiating bacterial species into two large groups (Gram-positive and Gram-negative) based on the chemical and physical properties of their cell walls. = bacteria = white blood cells Uses It is used to differentiate bacterial species into two large groups (Gram-positive and Gram-negative) based on the chemical and physical properties of their cell walls. Medical Gram stains are performed on body fluid or biopsy when infection is suspected. It yields results much more quickly than culture, and is especially important when infection would make an important difference in the patient's treatment and prognosis; examples are cerebrospinal fluid for meningitis and synovial fluid for septic arthritis. ...read more.


If the bacteria is Gram-positive it will retain the primary stain. If it is Gram-negative it will lose the primary stain and appear colorless. 5- Add the secondary stain, safranin, and incubate 1 min, then wash with water for a maximum of 5 seconds. If the bacteria is Gram-positive then the cell will retain the primary stain, will not take the secondary stain, and will appear black-violet. If the bacteria is Gram-negative then the cell will lose the primary stain, take secondary stain, and will appear red-pink. 2-The ELISA technique Enzyme-Linked ImmunoSorbent Assay or ELISA is a biochemical technique used mainly in immunology to detect the presence of an antibody or an antigen in a sample. The ELISA has been used as a diagnostic tool in medicine and plant pathology, as well as a quality control check in various industries. In simple terms, in ELISA an unknown amount of antigen is affixed to a surface, and then a specific antibody is washed over the surface so that it can bind to the antigen. This antibody is linked to an enzyme, and in the final step a substance is added that the enzyme can convert to some detectable signal. ...read more.


3- Tests with diffusion gradients of concentration. By this method, the test organism is seeded uniformly over an agar surface and exposed to a continuous concentration gradient of antibiotic diffusing from a paper disk (disk diffusion test). A bacterium sensitive to the antibiotic is inhibited from growing in a circular zone around the paper disk; the lower the MIC of the antibiotic for the organism, the larger the diameter of the zone. A comparison of the zone size with that produced in a parallel test with a control strain gives a measure of the MIC. Disk diffusion tests The disk diffusion method is still the most widely used for the routine sensitivity testing of isolates from patients. It is satisfactory for organisms that grow well overnight, i.e. for most of the common pathogenic aerobic and facultatively anaerobic bacteria, rapidly growing anaerobes such as Clostridium perfringens and Bacteroides fragilis, and rapidly growing fungi such as Candida albicans. It is unsuitable for slowly growing organisms, such as the tubercle bacillus, for the antibiotic would have become too diffused before growth had become visible. Several forms of disk diffusion test have been advocated, which vary in their methods of standardisation, reading and control. Disk of a single, usually high content of antibiotic are placed on an inocullum of strictly standardized density on Muller-Hinton agar. ...read more.

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