AST Flashcards
to determine the sensitivity or resistance of pathogenic aerobic and facultative bacteria
Antimicrobial susceptibility test
a manual for ZOI( Zone of inhibition
Clinical Laboratory Standard Institute
what are the material needed for AST:
Agar
0.5 Mcfarland
sterile cotton swab
Antibiotic disks
Wickerham Card
Method used in MHA
Kirby-Bauer Disk Diffusion Susceptibility test
The rate of Diffusion of the antimicrobial through the agar is dependent on the:
-Diffusion and Solubility properties of the drug in MHA
-Molecular weight of the antimicrobial compound
a material used behind the test tube to check the turbidity
Wickerham Card
what are the components of 0.5 McFarland Standard
- 99.5 ml of 1% sulfuric acid
- 0.5 ml of 1.175 Barium chloride
what is the total turbidity of 0.5 McFarland Standard
1.5 x 10^8 CFU/ml
material use t get the colonies in the agar
Sterile cotton Swab
disk diffusion of Broth microdilution
5 x 10^5 CFU/ml
pH of the Media
7.2 -7.4 (mostly alkaline)
Agar depth
3-5 mm (ave. 4mm)
suitable atmosphere of agar:
Humidified ambient air
Temperature of Agar
35 degrees celcius
thymidine content of agar
Minimal/ absent
excessive thymidine content in agar causes___
false resistance to trimethoprim
high pH on agar causes what
decrease nutrition of aminoglycosides
if Agar depth is < (less than) 3mm it causes___
false susceptible
if Agar depth is > (greater than) 3mm it causes___
False resistance
CO2 incubator causes what to MHA agar
decreases the pH, which decreases activating aminoglycosides
