Antimicrobial Susceptibility Test
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What is antimicrobial agents?
Substances used to kill prokaryotes
What produced antimicrobial agent?
What does antimicrobial include?
- All inclusive, anything that inhibits microbes
- Ex: amphyll, antibiotics
- Penicillin produced P. notatum (mold)
What is an example of synthetic antimicrobial?
Amoxicillin made after naturally occuring penicillin
What is antibiotic?
Natural substance that was produced by one microorganism to inhibit another mircoorganism
What is narrow spectrum drug?
- Drug target a specific type of bacteria
- Ex: Gram positive or gram negative targeting only
What is broad-spectrum antibiotics?
- Antibiotics that can kill off multiples types of microorganism
- Ex: both Gram positive and gram negative
What is Bacteriostatic?
Prevents microbial growth
What is MIC?
- Minimum Inhibitory Concentration: lowest antibiotic concentration that prevents bacterial growth
- Estimate using the E-test(E-epsilometer)
- Plastic strips with increasing (antibiotic)
What type of drugs can inhibit peptidoglycan cell wall synthesis?
Penicillins, Bacitracin, Vancomycin, Cephalosporin
Which drug inhibit protein synthesis?
Erythromycin, Tetracyclin, Streptomycin
Which drugs inhibit nucleic acid replication?
- Limited used due to affecting euk. DNA
- Quinolones, Rifampin
Which drugs injure plasma membrane?
- Polymyxin B
- Cause loss of essential metabolites from the cell
Which drug inhibit essential metabolites synthesis?
- Sulfanilamide, Trimethoprim
- inhibit enzymatic reaction
What is MRSA?
Methicillin-resistant Staphylococcus aureus
Is methicillin-resistant Staphylococcus aureus more virulent than normal Staphylococcus aureus?
No, just harder to treat with normal antibiotic
What is another name for disk diffusion method?
What is E-test?
Epsilometer test, more advanced diffusion method
Can E-test determine if a bacteria is bactericidal or bacteriostatic?
What is broth-dilution test?
Sequence of decreasing drug concentration in broth
How do we determine if the drug is bactericidal or bacteriostatic?
Inoculate the last well with no growth of bacteria with the drug concentration. If there is growth on plate after inoculation, then the drug is bacteroistatic. If there is no growth, then the drug is bactericidal. You can find the concentration of the drug when it is either bacteriostatic or bactericidal
What is the purpose of the Kirby-Bauer test(disk diffusion test)?
measure the effectiveness of antimicrobial drugs agains pathogen
What affect the size of zone of Inhibition?
Sensitivity to the drug
What happen when the drug has poorer solubility?
It has smaller zone of inhibition
What is the standard length of the Mueller-Hinton agar and why?
4 mm agar depth, 100 mm or 150mm Petri dishes.
What is in Mueller-Hinton agar?
- contain specific % of Barium Sulfate
- Produce turbidity and simulate growth
- Use test culture at the 0.5 McFarland (about 1.5X10^8
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