Differentiate between the diameter of inhibition and minimum inhibition concentration.
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The diameter of inhibition and minimum inhibition concentration (MIC) are both measures used to evaluate the effectiveness of antimicrobial agents. They provide information about the potency and the ability of the agent to inhibit or kill microorganisms. However, they assess different aspects of antimicrobial activity.
1. Diameter of inhibition: This measure is typically used in the Kirby-Bauer disk diffusion method, which is a commonly performed test to determine the susceptibility of microorganisms to antibiotics. In this method, paper discs containing a specific concentration of an antimicrobial agent are placed on an agar plate inoculated with the test organism. As the agent diffuses into the agar, it creates a zone of inhibition, which is an area around the disc where the growth of the microorganism is inhibited. The diameter of this zone is measured and recorded. A larger diameter of inhibition generally indicates greater efficacy of the antimicrobial agent against the organism tested.
2. Minimum inhibition concentration (MIC): The MIC is the lowest concentration of an antimicrobial agent required to inhibit the visible growth of a specific microorganism. It is typically determined using broth dilution or agar dilution methods. In these methods, a series of tubes or wells containing different concentrations of the agent are inoculated with the test organism. After incubation, the presence or absence of growth in each tube or well is observed. The lowest concentration of the agent that completely inhibits visible growth is recorded as the MIC. A lower MIC indicates a higher potency of the antimicrobial agent.
To summarize, the diameter of inhibition is measured by the Kirby-Bauer disk diffusion method and indicates the size of the zone where the organism's growth is inhibited. On the other hand, the MIC is a measure of the lowest concentration of the agent required to inhibit visible growth and is determined by broth or agar dilution methods. Both measurements provide valuable information about the effectiveness of antimicrobial agents, but they evaluate different aspects of their activity.