Module 7 Flashcards
(15 cards)
2 overall objectives of a clinical micro lab
- Perform bacterial ID
2. Perform antimicrobial susceptibility
Antimicrobial susceptibility
What antimicrobial would best kill or control the organism causing the infection?
Purpose of susceptibility (sensitivity) testing
Serves as a check on antimicrobials that are usually effective and detects the emergence of resistant strains
The goal of susceptibility testing
To provide a list of antimicrobials that would be effective against the organism responsible for a specific infection
3 conventional methods of performing antimicrobial susceptibility tests
- Broth dilution
- Agar dilution
- Disc diffusion
Questions we ask to choose the most appropriate antimicrobial for clinical use
- Is the antimicrobial effective at the pH found at the site of infection?
- Will the antimicrobial penetrate to the site of infection?
- Is it toxic to host tissue?
- Is it cost effective?
Some organisms do not have routine susceptibility tests performed because:
Standardized test methods are not available
They are universally susceptible to a suitable antimicrobial
pH of Mueller Hinton agar used for susceptibility testing
7.2-7.4 when the medium is ready to use
The concentration of divalent cations in susceptibility test medium affects results for:
aminoglycosides
MIC (minimum inhibitory concentration)
The minimum amount of antimicrobial inhibiting growth in vitro
The concentration of antimicrobial at the edge of the zone of inhibition in the Kirby Bauer test corresponds to:
The MIC
The concentration of thymidine in susceptibility test medium affects results for:
Sulfonamides
Mueller Hinton growth medium contains:
Beef infusion, acid hydrolysis of casein, starch, water
Susceptible/sensitive
The organism is susceptible to action of the antimicrobial and is killed by it or stops growing
Resistant
The organism is resistant to the action of the antimicrobial and keeps growing in its presence
