What are diffusion methods?

What are diffusion methods?

Disk diffusion by the Kirby-Bauer method is a standardized technique for testing rapidly growing pathogens. 89. Briefly, a standardized inoculum (i.e., direct suspension of colonies to yield a standardized inoculum is acceptable) is swabbed onto the surface of MH agar (i.e., 150-mm plate diameter).

What is the principle of 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 other methods can be used for antimicrobial susceptibility testing?

In-vitro antimicrobial susceptibility testing can be performed using a variety of formats, the most common being disk diffusion, agar dilution, broth macrodilution, broth microdilution, and a concentration gradient test.

Why use disk diffusion method?

The disk diffusion method is performed using Mueller-Hinton Agar (MHA), which is the best medium for routine susceptibility tests because it has good reproducibility, low in sulfonamide, trimethoprim, and tetracycline inhibitors, and gives satisfactory growth of most bacterial pathogens.

What is antibiotic diffusion?

Summary. Disc diffusion in agar is a common method of testing the sensitivity of bacteria to antibiotics. A microorganism is judged sensitive or resistant according to the diameter of the zone of inhibition of cultural growth, which is then correlated statistically with the minimal inhibitory concentration (MIC).

What is agar cup method?

penicillin by the cup method is performed by seeding a solid medium with a test organism and filling penicillin in cups, on or in the medium. During the growth of the organism the penicillin will diffuse into the medium so that its concentration will decrease with increasing distance from the cup.

What is the name of the antibiotic sensitivity test?

Sensitivity analysis, also called susceptibility testing, helps your doctor find the most effective antibiotic to kill an infecting microorganism. Infecting microorganisms are organisms such as bacteria or fungi that invade your body and cause an infection.

Is disk-diffusion qualitative?

The results of the disk diffusion test are “qualitative,” in that a category of susceptibility (ie, susceptible, intermediate, or resistant) is derived from the test rather than an MIC.

What is a 0.5 McFarland standard?

A 0.5 McFarland standard is prepared by mixing 0.05 mL of 1.175% barium chloride dihydrate (BaCl2•2H2O), with 9.95 mL of 1% sulfuric acid (H2SO4). Now there are McFarland standards prepared from suspensions of latex particles, which lengthens the shelf life and stability of the suspensions.