Antimicrobial Susceptibility Test: Disk Diffusion Method

What is the purpose of the disk diffusion method in antimicrobial susceptibility testing?

• To assess the temperature tolerance of the microorganisms

• To determine the color of the microorganisms

• To measure the pH of the growth medium

• To determine the susceptibility of microorganisms to specific antimicrobial agents.

Explain the process of preparing the agar plate for the disk diffusion method.

• The process involves preparing agar, pouring it into a petri dish, inoculating with bacteria, placing antibiotic disks, incubating, and measuring zones of inhibition.

• Skipping the incubation step

• Mixing the agar with water instead of agar powder

• Using a plastic bag instead of a petri dish

How are antibiotic disks placed on the agar plate during the disk diffusion method?

• Throwing the disks onto the agar plate from a distance

• Rubbing the disks vigorously on the agar plate

• Using sterile forceps to gently press the disks onto the agar plate surface.

• Placing the disks upside down on the agar plate

What is the significance of measuring the zone of inhibition in the disk diffusion method?

• It helps determine the color of the bacteria

• It measures the pH level of the antibiotic

• It helps determine the sensitivity of the bacteria to the antibiotic being tested.

• It indicates the size of the petri dish used

Describe how the results of the disk diffusion method are interpreted in terms of susceptibility or resistance.

• The interpretation is based on the color of the agar: red = susceptible, blue = resistant

• The interpretation is based on the size of the zone of inhibition: large zone = susceptible, small/no zone = resistant.

What factors can influence the results of the disk diffusion method?

• Type of antibiotic, concentration of antibiotic, incubation conditions, type of agar, growth rate of bacteria

• Type of food, temperature, color of agar

Compare and contrast the disk diffusion method with other methods of antimicrobial susceptibility testing.

• Disk diffusion method is only suitable for fungi, not bacteria, and lacks reproducibility, while other methods like broth dilution and E-test are versatile, applicable to all microorganisms, and provide consistent results.

• Disk diffusion method is qualitative, cost-effective, and easy to perform, providing susceptibility results, while other methods like broth dilution and E-test are quantitative, measuring MIC values.

• Disk diffusion method is quantitative, expensive, and difficult to perform, providing MIC values, while other methods like broth dilution and E-test are qualitative, measuring susceptibility results.

• Disk diffusion method is time-consuming, unreliable, and requires specialized equipment, providing resistance results, while other methods like broth dilution and E-test are quick, accurate, and cost-effective, measuring susceptibility results.

Discuss the importance of standardizing the disk diffusion method for accurate results.

• Accurate results can be achieved without following a standardized disk diffusion method.

• Standardizing the disk diffusion method is unnecessary and time-consuming.

• Varying testing conditions in the disk diffusion method do not affect the results.

• Standardizing the disk diffusion method is crucial for ensuring accurate and reliable results by maintaining consistent testing conditions.

Explain the concept of minimum inhibitory concentration (MIC) and its relationship to the disk diffusion method.

• MIC is determined by the size of the zone of inhibition in the disk diffusion method

• MIC is the lowest concentration of an antimicrobial agent that inhibits visible growth of a microorganism, while the disk diffusion method measures susceptibility by the zone of inhibition around disks with different concentrations of antimicrobial agents.

• MIC is the highest concentration of an antimicrobial agent that inhibits visible growth of a microorganism

• The disk diffusion method measures susceptibility by the color change of the agar around disks

What are some limitations of the disk diffusion method in antimicrobial susceptibility testing?

• Variations in diffusion rate, lack of standardization, inability to detect certain resistance mechanisms, limited ability to test certain antibiotics

• Variations in diffusion rate, lack of standardization, ability to detect all resistance mechanisms, limited ability to test certain antibiotics

• No variations in diffusion rate, lack of standardization, ability to detect all resistance mechanisms, limited ability to test certain antibiotics

• Consistent diffusion rate, standardized process, ability to detect all resistance mechanisms, broad ability to test antibiotics