Antimicrobial Sensitivity Testing: It’s Importance, Types, Methods and Interpretations

Antimicrobial susceptibility testing (AST) is a laboratory procedure performed by medical technologists to identify which antimicrobial regimen is specifically effective for individual patients. On a larger scale, it aids in the evaluation of treatment services provided by hospitals, clinics, and national programs for the control and prevention of infectious diseases. Clinical laboratories currently employ several methods depending on the laboratory test menu that they provide. These approaches include the disk diffusion and minimum inhibitory concentration (MIC) methods. Commercial systems also became available across health centers and hospital facilities, utilizing both phenotypic and genotypic characterization of bacterial resistance. While routine antimicrobial susceptibility testing for gram-positive (e.g., Staphylococcus aureus) and gram-negative bacteria (e.g., Pseudomonas aeruginosa) are commonly available in peripheral laboratories, drug susceptibility testing (DST) for Mycobacterium tuberculosis is usually carried out within more complex facilities like reference laboratories. Despite the differences in the techniques for susceptibility tests, all laboratories must be critical on each step of the sampling and testing process so that test results are obtainable with consistently high levels of accuracy and reliability. In this article, we elaborate the importance of AST, Standardization of Antimicrobial Sensitivity Testing (AST) Methods, Various types of AST including Disk Diffusion Method (Kirby Bauer method and Stokes method), Dilution methods (Broth dilution method and Agar dilution method), Epsilometer test and Automated Antimicrobial Susceptibility Test Systems (Vitek 2 systems, The MicroScan WalkAway system and The Phoenix system).