Antiseptics and Antibiotics (Kirby-Bauer test)
Antibiotics are defined as a chemical product that can inhibit or destroy pathogenic microorganisms.
Antiseptics are defined as chemicals that are able to inhibit in vitro sepsis. They do not kill the sepsis-producing agent, but inhibit its growth. Antiseptics are nontoxic to allow application to the skin and mucous membranes, such as Listerine.
The mode of action for these chemicals is the active denaturing of proteins within pathogenic organisms, cytoplasmic membrane dissolution, and act as oxidizing agents.
Clinical laboratories can test the potency of antibiotics and antiseptics by using the Kirby-Bauer test.A second example on this page includes a table for interpreting results according to critical diameters. You can determine from this table, assuming the test was done properly, if the bacterial agent is resistant, intermediate, or susceptible to the antibiotic that is being questioned.
Mueller-Hinton agar is the usual agar of choice for this procedure.
This test should be monitored closely, especially in the professional laboratory. Time limits and culture inoculum sizes should be within requirements for proper results. (Collegiate labs use a less restrictive Kirby-Bauer method).
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