There are three automated antimicrobial susceptibility test systems available and widely used at this time. All of them are MIC-based systems that follow the principle of determining the MICs by the broth microdilution method. The results provided by the systems are considered to be equivalent to that derived from broth dilution method. The procedure of microdilution test method involves making bacteria suspension to the standard concentration, preparing inoculum, rehy-drating and incubating culture media containing tested antimicrobials in various concentrations with the inoculum, reading bacteria growth pattern in the presence and absence of antibiotics, and finally reporting the MIC values. Most of those steps are performed by the devices within a self-contained instrument in the automated systems. The major differences among the systems are the methods to detect the bacteria growth and to obtain the MIC values.
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