Antimicrobial susceptibility testing


Do you know how a laboratory perform antimicrobial susceptibility to test for antibiotic resistance? There are couple of method as suggested by international regulatory bodies. One of the most common method is called disk diffusion test. When the laboratory technologist isolates a bacteria from a sample of concern, the bacteria are put into saline solution to make up a suspension meeting a standard concentration reference. Certain amount of this suspension is then being swabbed onto an agar plate, then antibiotic is applied onto the the agar surface in the form of an antibiotic impregnated filter disc. After standard incubation period, the zone represent bacterial inhibition is measured and result is interpreted with reference to international standard.

Sounds simple, but the impartance lies on the quality control of the whole procedure. Antimicrobial susceptibility testing is regulated by couple of international bodies which required testing to be performed in absolute high standard by every laboratory. Since the procedure involve many steps, every steps from agar plate manufacturing to antibiotic disc quality control have to be monitor very carefully to ensure quality results are produced in every testing.