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Medical Microbiology

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What is medical microbiology ? And technique how to play with microorganisms.

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Medical Microbiology

  1. 1. Submitted T o : Presented by : Rinki mishra Ankit sharma B.Sc. IIyr Dr. B. Lal Institute of Biotechnology
  2. 2.  Medical microbiology is both a branch of medicine and microbiology .  The branch of microbiology which deals with the characterization, prevention & control of disease-producing microorganisms in human beings is called Medical Microbiology. It deals with the infectious agents which cause diseases in man. It explain the bodily mechanisms that help fight disease.
  3. 3. INSTRUMENTS  INCUBATOR Incubator Digital Weighing Balance Laminar Air FLow Autoclave PH Meter
  4. 4. Preparation of Culture Media Isolation of Microorganism form clinical sample 1. Serial Dilution 2. Pour plate 3. Spread Plate 4. Streaking Characterization & Identification Morphological Microscopic Biochemical Antibiotic susceptibility test
  5. 5.  COMPLEX :– contains ingredients of unknown chemical composition. e.g. Potato dextrose agar.  DEFINED :– All chemical compositions are known. e.g. Czapek dox medium  SELECTIVE: - suppress unwanted microbes or encourage desired microbes. e.g. Endo agar, EMB, Mac Conkey agar TYPES OF MEDIA Culture Media : Contains all the nutrients required for the growth of microbes. Mac conkey agar Nutrient agar
  6. 6. SELECTIVE :- Suppress unwanted microbes or encourage desired microbes. e.g. BLOOD AGAR DIFFERENTIAL MEDIA: – Distinguish colonies of specific microbes from others. e.g. Endo agar, EMB, Mac Conkey agar. ENRICHED MEDIA :– Designed to increase the number of desired microbes to a detectable level. e.g. Blood agar.
  7. 7. AIM:– To obtain pure colonies of microbes SERIAL DILUTION METHOD – Inoculum subjected to serial dilution in normal saline , then spreading is done on agar plates.
  8. 8.  POUR - PLATE METHOD –  In this, successive dilutions of inoculum is added to molten agar in respective petriplates.  Individual colonies are picked for sub culturing. SPREAD – PLATE METHOD –  In this, dilute sample is placed onto solidified agar and is spread uniformly with sterile ,bent glass rod.
  9. 9. streak plate method. Principle: The streak plate methods often a most practical method of obtaining a discrete colonies and pure culture. It was originally developed by two Bacteriologist LOE LUEFF LOEFFLAR and GAFFKY in the laboratory of Robert Koch. In this method the satirized loop or transfer needle is dipped into a suitable diluted suspension of organisms which is already solidified in agar plate to make a series of parallel non-overlapping streaking. There are two type of Streaking 1) With Intermediate heat 2) Without Intermediate heat A) Radial streaking A) Continuous Streaking Results:- A confluent growth was seen where the initial streak was made, the growth is less dense away from the streak & discrete colonies farthest away from the streak (i.e. end of the streak) Figure: Streaking
  10. 10. When grown on a variety of media, microorganism will exhibits differences in the macroscopic appearance of their growth. These differences called cultural characterstics are used as a basis for separating microorganisms into taxonomic groups. Morphological Characteristics of Microorganism Irregular circular
  11. 11. • Gram Staining :  Used to differentiate b/w gram +ve & gram –ve bacteria.  Based on the difference in the composition of bacterial cell walls. • Primary Stain – Crystal Violet • Mordant - Iodine • Secondary Stain - Saffranin  Result :- gram +ve cell appears purple colour & gram –ve appearing pink colour.  Purple color : gram positive  (Staphylococcus)  Pink color : gram negative (E. coli) • Negative Staining  The acidic dye - INDIA INK OR NIGROSINE (acidic dye) • Does not stain the bacteria but stains the background. • Result :- spherical cells of staphylococcus aureus occurring single as well as cluster appear. Transparent (color less) against blue background Negative Stain Gram positive
  12. 12.  IMViC TEST This includes : - 1. INDOLE TEST : a) Medium : TRYPTONE BROTH Tryptophan + tryptophanase = indole + pyruvic acid b) Interpretation : Cultural tube + Kovac’s reagent Red layer : positive test (E.coli) Yellow or brown : negative test(Klebsiella Psuedomonas) 2.METHYL RED TEST: a) Medium : MRVP Broth It is based on the fermentation product of glucose . b) Interpretation :- Cultural broth + methyl red red layer : positive test (Pseudomonas) yellow layer : negative test (Klebseilla) 3.VOGES - PROSKAUER TEST Identifies bacteria that ferment glucose into 2,3 – butanediol. Medium : MRVP Broth Interpretation : cultural broth + Barritt’s reagent ; if cherry red : positive test (Klebseilla) if colour absent :- negative test (Pseudomonas) Figure: Voges – Proskauer Figure: Methyl Red TestFigure: Indole test
  13. 13. Citrate Utilisation Test  Based on the ability to use citrate as source of energy.  Medium : SIMMON’S CITRATE AGAR  Interpretation : - Blue : positive test ( Pseudomonas) No color change : negative test (E.coli). Catalase test :  Based on the ability to use catalase as source of energy. Medium: Hydrogen peroxide  Interpretation: – Air bubbles = +ve test (staphylococcus sp.) Figure: - Catalase testFigure: -Citrate Utilisation test
  14. 14.  Antibiotics susceptibility testing  Principle:This test determines the susceptibility of a microbial species against different antibiotic agents. The test is performed by the commonly used Agar Diffusion Method which is designed to determine the smallest amount of the antibiotic needed to inhibit the growth of micro-organism Figure: - Testing of anti-biotics activity Disk Diffusion Method Erythromycin E Vancomycin VA Levofloxacin LE Penicillin P Ampicillin AMP
  15. 15. THANK YOU…

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