ABSTRACT
Instrumentation in clinical microbiology has lagged far behind the level of automation present in chemistry and hematology and because clinical microbiologists historically have been skeptical of unconventional methods. This chapter examines those instrument systems that are designed for overnight determinations of antimicrobial susceptibilities. Basically, these systems represent mechanizations of preexisting manual systems, and, with one exception, utilize micro-dilution techniques. Instrumentation supporting microdilution systems has developed in a series of overlapping steps, beginning with the simple light box readers and evolving to the relatively high level of sophistication. In order to standardize the microdilution procedure, the effects of numerous variables have been studied. These include media and its supplements, inoculum size, physiologic condition of the inoculum, incubation time, stability during storage, evaporation, dilution error, and contamination. From many combined experiences, it seems clear that the microdilution technique is highly acceptable for routine antimicrobial testing.
