Antimicrobial susceptibility testing

Antimicrobial susceptibility testing, methods, standardizations, importance

1. Antimicrobial susceptibility testing Saajida Sultaana Mahusook

2. Susceptibility testing  is used to determine which antimicrobials will inhibit the growth of the bacteria or fungi causing a specific infection. Importance of Susceptibility testing The results from this  test   helps to determine which drugs are likely to be most effective in treating a person's infection. A ids in the evaluation of treatment services provided by hospitals, clinics and national programs for control and prevention of infectious diseases.  Monitor for resistance patterns due to the mutations in bacterial DNA.

3. Standardizations in vivo Different standards for methodology CLSI EUCAST Standard media Mueller Hinton Agar or broth S tandardized inoculum ATCC strain Isolation and standardizing the bacterial suspension by McFarland standards Performing tests under standard conditions Incubation time and temperature Volume of the media used Size and Dilution of the inoculum pH and contents of the medium Use of QC strains for further check and reference

4. Methods for testing Antimicrobial Susceptibility Disk dilution Broth dilution Agar dilution Commercial systems like health centers and hospital facilities, utilize both phenotypic and genotypic characterization of bacterial resistance . Qualitative result indicate how a bacteria may respond to a drug in vivo (RIS) . Quantitative result indicated by Minimal inhibitory concentration (MIC ).

5. M inimum inhibitory concentration (MIC) It is the lowest concentration of an antimicrobial drug that will inhibit the visible growth of a microorganism after overnight incubation.  Minimum inhibitory concentration (MIC) can be determined by culturing microorganisms in liquid media or on plates of solid growth medium . A lower MIC value indicates that less drug is required for inhibiting growth of the organism; therefore, drugs with lower MIC scores are more effective antimicrobial agents . By identifying appropriate drugs and their effective concentrations, MIC scores aid in improving outcomes for patients and preventing evolution of drug-resistant microbial strains.

6. Qualitative measurement Agar dilution Disk Diffusion method (DD) Devised by Kirby Bauer Use different concentration of antimicrobials against an inoculum. Measure diameter of the zone of inhibition (MIC)

7. Broth dilution To Determine MIC

8. Broth microdilution method

9. E- test Combines Agar dilution and Disk diffusion method Use of strip that has different concentration of antimicrobial To determine MIC

10. Reference https://www.coursera.org/learn/antimicrobial-resistance/home/week/2 https:// labtestsonline.org/tests/antibiotic-susceptibility-testing https://www.ncbi.nlm.nih.gov/books/NBK539714 / https://courses.lumenlearning.com/boundless-microbiology/chapter/measuring-drug-susceptibility/ THANK YOU