Why is the disk diffusion method not a perfect indication of how the drug will perform in vivo what other factors must be considered before using the antimicrobial agent in vivo?

Why is the disk diffusion method not a perfect indication of how the drug will perform in vivo what other factors must be considered before using the antimicrobial agent in vivo?

an antibiotic is determined by testing for bacterial growth in dilutions of the antibiotic in nutrient broth. why is the disk diffusion technique not a perfect indication of how the drug will perform in vivo? patient size, age and other physical conditions as well as side effects and other drugs must be considered.

What are the methods used for measuring antimicrobial activity?

A variety of laboratory methods can be used to evaluate or screen the in vitro antimicrobial activity of an extract or a pure compound. The most known and basic methods are the disk-diffusion and broth or agar dilution methods. Other methods are used especially for antifungal testing, such as poisoned food technique.

How can you determine whether this antibiotic is either bacteriostatic or bactericidal?

Defining bactericidal and bacteriostatic The formal definition of a bactericidal antibiotic is one for which the ratio of MBC to MIC is ≤ 4, while a bacteriostatic agent has an MBC to MIC ratio of > 4.

What is the principle of the agar disc diffusion method?

This method is based on the principle that antibiotic-impregnated disk, placed on agar previously inoculated with the test bacterium, pick-up moisture and the antibiotic diffuse radially outward through the agar medium producing an antibiotic concentration gradient.

What are the limitations of the disk diffusion assay?

There are serious limitations to the use of disk diffusion method. Results may be unexpected or borderline. In such cases another method of testing may be required or the test may need to be repeated for confirmation.

What is disk diffusion test used for?

Disk-diffusion susceptibility testing is most frequently used to measure the antimicrobial resistance of isolates of N. gonorrhoeae for patient management whereas determination of the minimal inhibitory concentration (MIC) is more appropriate for surveillance programs.

What is the benefit of disk diffusion method test?

Disk diffusion has many advantages, as it is cheap, flexible and allows visibility of growth, correct inoculum, mixed cultures and other abnormalities. Another benefit is the possibility of executing direct susceptibility testing (DST).

What is the disc diffusion method used for?

In diagnostic laboratories, the disk diffusion test is used to determine the susceptibility of clinical isolates of bacteria to different antibiotics. An effective antibiotic will produce a large zone of inhibition (disk C), while an ineffective antibiotic may not affect bacterial growth at all (disk A).

How do you measure disk diffusion?

Take a ruler or caliper that measures in millimeters and place the “0” in the center of the antibiotic disk. Measure from the center of the disk to the edge of area with zero growth. Take your measurement in millimeters. This measures the radius of the zone of inhibition.

What factors affect the size of the zone of inhibition for each antibiotic?

The medium influences the size of the zone by its effect on the rate of growth of the organism, the rate of diffusion of the antibiotic, and the activity of the agent.

What are the factors affecting diffusion assay?

Agar nutrient content, cylinder charge volume, thickness (volume) of the agar layer, and incubation temperature were 4 factors varied to determine their effect(s) on the optimization of the cylinder-plate diffusion assay.

What would happen if we didn’t use aseptic technique to put the antibiotic disk on the plate?

What would happen if we didn’t use aseptic technique to put the antibiotic disk on the plate? In these cases, changes in antibiotic concentration might not show as much effect as one would expect. Antibiotics can be bactericidal (they kill the microbe) or bacteriostatic (they inhibit microbial growth, but do not kill).