What are the limitations of the disk diffusion method?
However, the disk diffusion test has additional limitations that should be considered. Training and experience are required both for performing and reading the results. Further, the test is labor-intensive and has similar limitations to other culture-based tests.
What factors affect the size of the zone of inhibition for each antibiotic?
There are multiple factors that determine the size of a zone of inhibition in this assay, including drug solubility, rate of drug diffusion through agar, the thickness of the agar medium, and the drug concentration impregnated into the disk.
What is the advantage of disc diffusion method?
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 Kirby Bauer disc diffusion method?
The purpose of the Kirby-Bauer disk diffusion susceptibility test is to determine the sensitivity or resistance of pathogenic aerobic and facultative anaerobic bacteria to various antimicrobial compounds in order to assist a physician in selecting treatment options for his or her patients.
What is broth Microdilution method?
Broth microdilution is the standard method used in most reference laboratories in the United States and abroad. The method typically tests twofold dilutions of multiple antimicrobial agents in 96-well disposable plastic trays (Figure 2).
How does disk diffusion work?
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 factors might affect the size of the zone of inhibition during a disk diffusion test?
Factors influencing the size of inhibition zones in DDM and AMD include the size of the filter paper disk or hole, the amount of compound placed onto the disk or into the hole, the type and concentration of the agar, the thickness and pH of the medium, the microbial strain tested, and the incubation temperature.
What is the difference between disc diffusion and well diffusion?
The key difference between agar well and disc diffusion method is that in agar well diffusion method, the extract solution is filled into a hole or a well created on the agar medium while in agar disc diffusion method, a filter paper disc containing the test solution is placed on the agar surface.
What are the limitations of the disk diffusion test?
There are serious limitations to the use of disk diffusion method. Results may be unexpected or borderline. 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 in microbiology?
Disk Diffusion Method. The disk diffusion method (DDM) is classified as an agar diffusion method (ADM) because the plant extract to be tested diffuses from its reservoir through the agar medium seeded with the test microorganism. Generally, the reservoir is a filter paper disk, which is placed on top of an agar surface.
What is disk diffusion method (DDM)?
The disk diffusion method (DDM) is classified as an agar diffusion method (ADM) because the plant extract to be tested diffuses from its reservoir through the agar medium seeded with the test microorganism. Generally, the reservoir is a filter paper disk, which is placed on top of an agar surface.
What is the history of disc diffusion test?
As the Broth dilution method are time-consuming, many laboratories in the United States adopted disc diffusion tests in the early 1950s. Kirby Bauer tests also known as the Disc diffusion test is used for antibiotic susceptibility testing. Lacks of standardization creates a problem in the 1960s and later Kirby and Bauer reviewed the description.