Question

Culture method used for sensitivity testing are :

• A. Anaerobic culture
• B. Pour plate culture
• C. Streak culture
• D. Lawn culture

Answer 1

Answer:

D. Lawn culture

Overview of Antimicrobial Susceptibility Testing (AST)

• Antimicrobial Susceptibility Testing (AST) is a laboratory procedure used to determine which antimicrobial agents will inhibit the growth of bacteria or fungi causing a specific infection.

• The results of these tests guide clinicians in selecting the most effective antibiotic therapy for patients.

Common Culture Methods for Sensitivity Testing

• Kirby-Bauer Disk Diffusion Method: This is the most widely used standardized method. Bacteria are inoculated onto an agar plate (typically Mueller-Hinton agar), and antibiotic-impregnated paper disks are placed on the surface. After incubation, the zone of inhibition around each disk is measured to determine susceptibility.

• Broth Dilution Method: This method involves testing serial dilutions of an antimicrobial agent in a liquid culture medium (broth). It provides both qualitative and quantitative data, specifically determining the Minimum Inhibitory Concentration (MIC)—the lowest concentration of an antibiotic that prevents visible growth.

• E-test (Epsilometer test): This is a variation of the disk diffusion method. It uses a plastic strip impregnated with a concentration gradient of an antibiotic. It allows for the direct reading of the MIC value on the strip.

• Agar Dilution Method: Involves incorporating specific concentrations of an antimicrobial agent directly into the agar medium. It is considered a reference method for determining MIC but is more labor-intensive compared to disk diffusion.