際際滷

際際滷Share a Scribd company logo

Antibiotic sensitivity test.

Download as PPTX, PDF
Animal Health Research Institute
Animal Health Research Institute

The presentation about the principles, procedures, and result interpretation of antibiotic sensitivity test

1 of 39
Download to read offline
Antibiotic sensitivity tests Prepared by Dr Mohammed Iraqi Assistant researcher at animal Health Research Institute (AHRI), GIZA, Egypt
Definition A test done to check the effectiveness of a drug against a bacterium and to select the best drug that acts against the bacterium. The in vitro testing of bacterial cultures with antibiotics to determine susceptibilityofbacteriatoantibiotictherapy
Antibiotic sensitivity test.
Why Need continues for testing for Antibiotic Sensitivity? Bacteria can develop resistance following repeated or subclinical (insufficient) doses, so more advance antibiotics and synthetic antimicrobials are continually required to overcome them.
Qualitative Methods Quantitative Methods
Diffusion methods: Principle: A paper disk with a defined amount of antibiotic is used to generate a dynamically changing gradient of antibiotic concentrations in the agar in the vicinity of the disk.
Antibiotic sensitivity test.
The antibiotic contained in a reservoir diffuses out of the disk to form the gradient. The test organism starts to divide and grow and progresses toward a critical mass of cells. Inhibition zone is formed at the critical time where a particular concentration of the antibiotic is just able to inhibit the organism before it reaches an overwhelming cell mass.
Antibiotic sensitivity test.
Antibiotic sensitivity test.
Mueller- Hinton-Agar: Medium containing beef infusion, peptone, and starch. Used primarily for the disk-diffusion method.
Antibiotic disks: Any commercially available discs with the proper diameter and potency can be used. Stocks of antibiotic discs can be stored at -20 属C for 1 month. On removal from the refrigerator, the containers should be left at room temperature for about 1 hour to allow the temperature to equilibrate.
Turbidity standards: Standard inoculum should have turbidity equivalent to 0.5 McFarland standard. Should be from a freshly overnight growth. These are made by dissolving barium sulphate in water with different concentration. 0.5 McFaraland have a turbidity equivalent to 1x 105
Cotton swabs
Procedures Application o f Antibiotic Discs Incubation At 35C for 16 -18 hours Measurement of inhibition zone diameter
1- To prepare the inoculum from the primary culture plate, touch with the loop the tops of 3-5 colonies of similar appearance of the organism to be tested.
2-Transfer this growth to a tube of saline or MHB (Mueller-Hinton-Broth) and incubate the tube in 37 for (0.5- 2 hours).
3- Compare the tube to adjust with the turbidity standard by adding more bacteria or more sterile saline.
Antibiotic sensitivity test.
the swab all over the surface of the medium three times, rotating the plate through an angle of 60 after each application. Finally, pass the swab round the edge of the agar surface.
7-Leave the inoculum to for a few minutes at room temperature with the lid closed. 8-The antibiotic discs may be placed on the inoculated plates using sterile forceps. a template. a sterile needle tips. antibiotic disc dispenser.
Antibiotic sensitivity test.
A maximum of can be placed on a 910 cm plate. Six discs may be spaced evenly, approximately 15 mm from the edge of the plate, and 1 disc placed in the center of the plate. The plates should be incubated within 30 minutes of preparation.
Strips of multiple antibiotics can be placed in one go
Measurement of inhibition zone diameter Using a ruler on the under-surface of the plate containing transparent medium. Using a pair of calipers on the plate containing opaque medium.
Measurement of diameter using automated zone readers
Interpretation of results:(according to standard zone diameter detected by CLSI (Clinical and Laboratory Standard Institute Interpretative chart of zone sizes Diameter of zone inhibition (mm) Antibiotic Resistant Intermediate Susceptible Tetracycline <14 15-18 >19 Chloramphenicol <12 13-17 >18 Cotrimoxazole <10 11-15 >16 _ Erythromycin <13 14-22 Gentamycin <12 13-14
Stokes method
Antibiotic sensitivity test.
Dilution method: Used to determine the minimal concentration of antibiotic to inhibit or kill the microorganism. Achieved by dilution of antibiotic in either agar or broth media.
Minimum inhibitory concentration (MIC):
Antibiotic sensitivity test.
Antibiotic sensitivity test.
E-test Epsilometer Test Quantitative method of antibiotic sensitivity testing. Applies both dilution of antibiotic and diffusion of antibiotic into the medium. Combines the principles of disk diffusion and agar dilution methods
Antibiotic sensitivity test.
Interpretation of E-test
USES OF E-test: Detecting Glycopeptide-resistant Enterococci (GRE) Glycopeptide-intermediate S. aureus (GISA) Resistant Mycobacterium tuberculosis Extended spectrum beta lactamases (ESBL)
Antibiotic sensitivity test.
Antibiotic sensitivity test.

More Related Content

Antibiotic sensitivity test.

  • 1. Antibiotic sensitivity tests Prepared by Dr Mohammed Iraqi Assistant researcher at animal Health Research Institute (AHRI), GIZA, Egypt
  • 2. Definition A test done to check the effectiveness of a drug against a bacterium and to select the best drug that acts against the bacterium. The in vitro testing of bacterial cultures with antibiotics to determine susceptibilityofbacteriatoantibiotictherapy
  • 4. Why Need continues for testing for Antibiotic Sensitivity? Bacteria can develop resistance following repeated or subclinical (insufficient) doses, so more advance antibiotics and synthetic antimicrobials are continually required to overcome them.
  • 6. Diffusion methods: Principle: A paper disk with a defined amount of antibiotic is used to generate a dynamically changing gradient of antibiotic concentrations in the agar in the vicinity of the disk.
  • 8. The antibiotic contained in a reservoir diffuses out of the disk to form the gradient. The test organism starts to divide and grow and progresses toward a critical mass of cells. Inhibition zone is formed at the critical time where a particular concentration of the antibiotic is just able to inhibit the organism before it reaches an overwhelming cell mass.
  • 11. Mueller- Hinton-Agar: Medium containing beef infusion, peptone, and starch. Used primarily for the disk-diffusion method.
  • 12. Antibiotic disks: Any commercially available discs with the proper diameter and potency can be used. Stocks of antibiotic discs can be stored at -20 属C for 1 month. On removal from the refrigerator, the containers should be left at room temperature for about 1 hour to allow the temperature to equilibrate.
  • 13. Turbidity standards: Standard inoculum should have turbidity equivalent to 0.5 McFarland standard. Should be from a freshly overnight growth. These are made by dissolving barium sulphate in water with different concentration. 0.5 McFaraland have a turbidity equivalent to 1x 105
  • 15. Procedures Application o f Antibiotic Discs Incubation At 35C for 16 -18 hours Measurement of inhibition zone diameter
  • 16. 1- To prepare the inoculum from the primary culture plate, touch with the loop the tops of 3-5 colonies of similar appearance of the organism to be tested.
  • 17. 2-Transfer this growth to a tube of saline or MHB (Mueller-Hinton-Broth) and incubate the tube in 37 for (0.5- 2 hours).
  • 18. 3- Compare the tube to adjust with the turbidity standard by adding more bacteria or more sterile saline.
  • 20. the swab all over the surface of the medium three times, rotating the plate through an angle of 60 after each application. Finally, pass the swab round the edge of the agar surface.
  • 21. 7-Leave the inoculum to for a few minutes at room temperature with the lid closed. 8-The antibiotic discs may be placed on the inoculated plates using sterile forceps. a template. a sterile needle tips. antibiotic disc dispenser.
  • 23. A maximum of can be placed on a 910 cm plate. Six discs may be spaced evenly, approximately 15 mm from the edge of the plate, and 1 disc placed in the center of the plate. The plates should be incubated within 30 minutes of preparation.
  • 24. Strips of multiple antibiotics can be placed in one go
  • 25. Measurement of inhibition zone diameter Using a ruler on the under-surface of the plate containing transparent medium. Using a pair of calipers on the plate containing opaque medium.
  • 26. Measurement of diameter using automated zone readers
  • 27. Interpretation of results:(according to standard zone diameter detected by CLSI (Clinical and Laboratory Standard Institute Interpretative chart of zone sizes Diameter of zone inhibition (mm) Antibiotic Resistant Intermediate Susceptible Tetracycline <14 15-18 >19 Chloramphenicol <12 13-17 >18 Cotrimoxazole <10 11-15 >16 _ Erythromycin <13 14-22 Gentamycin <12 13-14
  • 30. Dilution method: Used to determine the minimal concentration of antibiotic to inhibit or kill the microorganism. Achieved by dilution of antibiotic in either agar or broth media.
  • 34. E-test Epsilometer Test Quantitative method of antibiotic sensitivity testing. Applies both dilution of antibiotic and diffusion of antibiotic into the medium. Combines the principles of disk diffusion and agar dilution methods
  • 37. USES OF E-test: Detecting Glycopeptide-resistant Enterococci (GRE) Glycopeptide-intermediate S. aureus (GISA) Resistant Mycobacterium tuberculosis Extended spectrum beta lactamases (ESBL)