In the Kirby-Bauer disk diffusion test, the concentration of the antibacterial agents is crucial for determining their efficacy against bacteria. However, macadamia oil and herbal extracts (like gentian or other herbal extracts) are not typically evaluated in the same way as standardized antibiotics used in this method.
For such substances, it may not be possible to follow conventional concentrations used for antibiotics. Instead, researchers might prepare a range of different concentrations of the oil or extract, typically from 1% to 10% in a suitable solvent or medium (like Dimethyl Sulfoxide (DMSO) or culture medium) to evaluate their antimicrobial activity.
The essential procedure would involve:
- Preparing a bacterial suspension of a known concentration (usually around 0.5 McFarland standard).
- Inoculating agar plates (like Mueller-Hinton agar) with the bacterial suspension.
- Soaking sterile filter paper disks in various concentrations of macadamia oil or herbal extract.
- Placing the disks onto the inoculated agar plates.
- Incubating the plates for 18-24 hours at 35-37°C.
- Measuring the diameter of the inhibition zone around each disk to assess antimicrobial activity.
If conducting such tests with macadamia oil or herbal extracts, it is essential to first establish the concentration range to assess the antimicrobial effects appropriately. Each study may have its specific guidelines, and pilot testing may be necessary to identify effective concentrations.