Exercise 9

CHEMICAL AGENTS OF MICROBIAL GROWTH CONTROL: AGAR WELL DIFFUSION ASSAY

• Chemical Methods of Control: Involves the use of antibiotics or inorganic or organic chemicals known as antiseptics or disinfectants.

• Phenol: acts as a protoplasmic poison by penetrating and disrupting the cell wall and the cell membrane resulting to leakage of cell components.

• Alcohols: Bactericidal and Fungicidal, they denature proteins and dissolve lipid complexes in the cell membrane.

Depending on the concentration of the chemical and the length of exposure, a chemical may be microbicidal or microbiostatic.

Chemotherapeutic agents may have specific, or broad-spectrum activity.

• specific: effective to only one group of microorganism

• broad-spectrum: effective to a wide variety of microbes

To determine a microorganism’s drug susceptibility, diffusion assays such as the agar well, and the Kirby-Bauer method are employed.

These methods allow for the rapid determination for the efficacy of drugs by measuring the diameter of the zone of inhibition resulting from the activity of the agent against the microorganism.