Reliability of the Kirby-Bauer Disc Diffusion Method for Detecting Methicillin-Resistant Strains of Staphylococcus aureus

Abstract

The resistance of Staphylococcus aureus to methicillin and related drugs can be reliably determined by using the Kirby-Bauer method of susceptibility testing if the incubation temperature is 35 C or below, but resistance may be missed at 37 C. The 1-μg discs of oxacillin and nafcillin or the 5-μg discs of methicillin may be used for this purpose but not the 1-μg discs of cloxacillin. The latter fail to discriminate between sensitive and resistant staphylococci by zone measurement; some resistant strains of staphylococci may show larger zones of inhibition than sensitive strains. Stability of these antibiotic-containing discs was studied under conditions of temperature and humidity variation that might be encountered in a clinical laboratory refrigerator. Oxacillin discs were the most stable and are to be preferred for susceptibility testing. Nafcillin discs were less stable, and methicillin discs lose their potency rapidly unless carefully stored in a refrigerator with a desiccant.

Sesquiterpenes and Monoterpenes from the Leaves and Stems of Illicium simonsii and Their Antibacterial Activity

“…The antimicrobial activity of the I. simonsii extract was carried out by the disc diffusion method according the literature [ 30 ]. Briefly, the test sample was first dissolved with DMSO to obtain a concentration of 1280 μg/mL solution, the inoculums of microorganisms were spread over nutrient agar plates with a sterile swab, and sterilized metrical filter paper discs were soaked with 10 μg/disc concentration of the test samples.…”

Biofunctionalization of Porous Ti Substrates Coated with Ag Nanoparticles for Potential Antibacterial Behavior

“…For the reasons stated above, the study of antibacterial behavior was carried out on discs superficially modified (hydroxylated) with the piranha reagent followed by silanization and then submerged in the suspension of silver nanoparticles. To demonstrate the effectiveness of AgNPs coating, a qualitative experiment of bacterial growth inhibition was conducted using Staphylococcus aureus as a Gram+ bacterial model [73]. Initially, tests were performed on fully dense discs comparing the antimicrobial effect on only silanized samples and samples with a silanization and AgNP-coating treatment.…”

The mice’s hematological effect of given the Staphylococcus aureus and Persea americana

“…The extract was then concentrated in the form of a paste and the sensitivity of S. aureus was tested using the Kirby-Bauer Disc Diffusion Method in order to obtain the optimal concentration of testing in experimental mice. [19] Erythromycin and tetracycline were used as antibiotic controls.…”