Antimicrobial Susceptibility Testing

The majority of infectious diseases are bacterial in origin. With the discovery of laboratory methods to grow these microorganisms using an appropriate growth medium known as “culture,” determining the sensitivity and resistance of specific pathogens to a wide range of antimicrobial agents is necessary so clinicians can immediately institute proper treatment regimens. Antimicrobial susceptibility testing is a laboratory procedure performed by medical technologists (clinical laboratory scientists) to identify which antimicrobial regimen is effective for individual patients. On a larger scale, the testing aids in evaluating treatment services provided by hospitals, clinics, and national programs to control and prevent infectious diseases. Recently, researchers have had to implement continuous surveillance activities for resistance patterns due to the mutations in bacterial deoxyribonucleic acid.

Clinical laboratories currently employ several methods depending on their laboratory test menu. These approaches include the disk diffusion and minimum inhibitory concentration (MIC) methods. Commercial systems are also available across health centers and hospital facilities, utilizing phenotypic and genotypic characterization of bacterial resistance. While routine antimicrobial susceptibility testing for gram-positive (eg, Staphylococcus aureus) and gram-negative bacteria (eg, Pseudomonas aeruginosa) are commonly available in peripheral laboratories, drug susceptibility testing 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 are critical in each step of the sampling and testing process so that test results are obtained with consistently high levels of accuracy and reliability.