Advanced Phenotypic Antimicrobial Susceptibility Testing Methods

Abstract

Phenotypic antimicrobial susceptibility testing methods remain the gold standard for clinical microbiology laboratories due to their advantage of being standardized as well as their having been integrated with both pharmacokinetic and pharmacodynamic principles, which allows clinically relevant breakpoints and optimal dosing. The main disadvantage of phenotypic methods is the length of time that these require. Genotypic molecular methods thus have been developed that identify pathogens and resistance markers directly from clinical specimens; these methods are discussed in other chapters. Direct antimicrobial susceptibility testing means that the clinical specimen serves as the inoculum; generally, this means that genomic molecular methods are used to detect resistance genes. In contrast, rapid phenotypic susceptibility testing methods mean that detection of growth from a pure culture with a defined inoculum is determined more rapidly than can be done with traditional methods. Traditional phenotypic susceptibility test methods can be accelerated using several different approaches. In addition, novel approaches for phenotypic antimicrobial susceptibility testing are being investigated as well. This chapter will address these advanced phenotypic susceptibility testing methods.