Antibiotic sensitivity testing sahar mohadret bokra

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Antibiotic sensitivity testing sahar mohadret bokra

  1. 1. Pathogenic Microorganisms
  2. 2. Pathogenic Microorganisms  Bacteria  Fungi  Parasites
  3. 3. Culture and Sensitivity
  4. 4. Identification of Bacteria Bacteria Gram’s Stain Gram’s +ve Gram’s -ve Cocci Bacilli Cocci Rods
  5. 5. Microscopical Examination: •Examination of wet mount preparation. •Examination of stained preparation. Identification of Bacteria Macroscopical Examination:Macroscopical Examination: • Characters of colonies.Characters of colonies. • Hemolysis on blood agar.Hemolysis on blood agar. • Pigment production.Pigment production.
  6. 6. Biochemical Tests: •Primary tests. •Secondary tests. Identification of Bacteria Additional Tests:Additional Tests: • such as seriological testssuch as seriological tests
  7. 7. Standardized Disc-Agar Diffusion Method by
  8. 8. Variables Affecting the Results of Sensitivity Testing
  9. 9. • Components of the medium: Examples: * PABA antagonizes Sulfonamides * Ca2+ antagonizes Tetracyclines • pH of the medium: It should be adjusted in the range 7.2 – 7.4 Acidity Activity of tetracycline and methicillin Activity of Aminoglycosides and Erythromycin 1.Medium Mueller – Hinton Agar
  10. 10. • Should be standardized to be 105 – 106 cfu / ml. • This can be achieved by visual matching the turbidity of the broth culture with a 0.5 McFerland Standard Suspension. • The apparent sensitivity of the organism is inversely proportional to the inoculum size. • A resistant mutant is much more likely to emerge in large population. 2.Inoculum Size
  11. 11. 3.Incubation condition • IncubationPeriod: The usual incubation time for sensitivty testing should be 16 -18 hrs * Sometimes, the microorganism is not killed but only inhibited upon short exposure to antimicrobial agents * The longer the incubation period, the greater chance for resistant mutants to emerge. • IncubationTemperature: Should be adjusted at 35o C. N.B: Several antimicrobial agents may loose their activity at this temperature. eg: Chlortetracycline
  12. 12. 4.Selection of Antimicrobials Microorganism. Spectrum of the antibiotic Patient condition.
  13. 13. s Test microorganism: S.aureus , E.coli or Pseudomonas. Mueller-Hinton agar plate.Mueller-Hinton agar plate. Sterile cotton swab.Sterile cotton swab. P s Set of standardized antibiotic discs.Set of standardized antibiotic discs.
  14. 14. Procedure: Adjust turbidity of the culture to be equal to 0.5 McFerland Standard Suspension. Inoculate Mueller-Hinton agar plate by streaking the test organism in three different dimensions.
  15. 15. Procedure: Adjust turbidity of the culture to be equal to 0.5 McFerland Standard Suspension. Inoculate Mueller-Hinton agar plate by streaking the test organism in three different dimensions.
  16. 16. Procedure: Apply the antibiotic discs by means of sterile forceps.
  17. 17. Procedure: Apply the antibiotic discs by means of sterile forceps. Incubate at 35o C for 16 – 18 hrs. F10 S10 AmG10 SXT
  18. 18. Results: Measure the diameter of each inhibition zone *The diameter of the inhibition zones are directly proportional to the susceptibility of the microorganism to the antibiotics. F10 S10 AmG10 SXT
  19. 19. Results: Disc Antibiotic Zone diameter (mm( Susceptibility Am30 S10 F10 Amikacin Streptomycin Fucidine 9 14 25 R I S Antimicrobial agent Disk content (µg( Resistant Intermediate Susceptible Amikacin Streptomycin Fucidine 30 10 10 ≥14 ≥11 ≥14 15-16 12–14 15-21 ≤17 ≤15 ≤22 Zone diameter (mm(
  20. 20. ‫بخير‬ ‫وأنتم‬ ‫عام‬ ‫كل‬ With my Best Wishes,,, Manal Abu El-Khair

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