Rapid Systems and Instruments for Antimicrobial Susceptibility Testing of Bacteria

Antimicrobial susceptibility testing (AST) can be performed by four basic methods: disk diffusion, broth dilution, agar dilution, and gradient diffusion. The authors recognize that susceptibility testing methods and panels are subject to periodic modifications and that new systems and panels are introduced into various global markets as an ongoing process. This chapter reviews recently published evaluations of currently used commercial systems. The automated and semiautomated systems discussed in the chapter have the capability of producing standardized or customized patient test reports generated by computer software packages that are referred to as data management systems (DMS). In the chapter, five current automated systems are discussed individually and evaluations (advantages and limitations) are presented as an overview of the current literature. The automated Sensititre ARIS system is a broth microdilution method utilizing a standard 96-microwell panel containing serial dilutions of dehydrated antimicrobial agents. Panel configurations are currently available for gram-positive and gram-negative bacteria in either a MIC-only format or a breakpoint format and are listed in the chapter. The chapter describes published evaluations of several commercial MIC methods for Staphylococcus pneumoniae, and reviews several commercial methods for the rapid detection of methicillin-resistant S. aureus (MRSA).