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Antimicrobial Susceptibility, MIC and MBC
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Microbiology Lab Report 3
Carolina Toscanojara

Antibiotic Sensitivity.

Objective:
Antibiotics are chemical compounds that selectively interfere with the growth of microorganisms while causing little or no damage to the animal or human host. The purpose of this lab was to determine the effectiveness antibiotics against any given bacterium by means of examining the zone of inhibition, the minimum inhibitory concentration, and the minimum bactericidal concentration.

Introduction: Chemical antimicrobial agents are chemical compounds that are capable of either preventing the microorganisms for multiplying (bacteriostatic) in order for the immune system of the host to overcome them or killing them completely (bactericidal). Antibiotics taken to improve the symptoms from a disease are called chemotherapeutic drugs; they are produced by a microorganism such as bacterium or fungus and/or are derived from a chemical produced by one. The test carried out to determine which antibiotic will be most successful in treating certain bacteria is called Antibiotic Susceptibility Test (AST) and it is often done by the Kirby-Bauer method, which uses Muller Hinton agar and paper discs containing specific concentrations of antibiotics are placed on the agar surface after rubbed with bacterial specimen. Results of AST are examined for zones of inhibition around each disk after incubation; this is called minimum inhibitory concentration (MIC). The diameter of the zone of growth inhibition is measured and scored according to the size of the zone and the particular antibiotic as sensitive, intermediate, or resistant. If the zone of inhibition is equal to or greater than the standard, the organism is considered to be sensitive to the antibiotic.