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Category: Clinical Microbiology
Susceptibility Testing Instrumentation and Computerized Expert Systems for Data Analysis and Interpretation, Page 1 of 2
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Commercial antimicrobial susceptibility testing (AST) systems were introduced into clinical microbiology laboratories during the 1980s and have been used in the majority of laboratories since the 1990s. Manual and semiautomated broth microdilution systems are utilized for small volumes of susceptibility testing, while larger laboratories often choose an automated broth microdilution system. The AST systems include data management software that may be interfaced with a laboratory information system (LIS) and offer various levels of expert system and epidemiological analyses. This chapter focuses primarily on commercial susceptibility testing systems currently available in the United States. It discusses advantages and disadvantages of automated systems. Reports of AST performance for detecting problematic resistance phenotypes are also discussed. Expert systems to assist in the critical review of AST results are available for all commercial susceptibility systems currently marketed in the United States. Most expert systems use a rules-based approach focusing on AST results for one drug at a time without considering results for other agents tested simultaneously. Factors to consider when selecting an AST system include cost, performance, work flow, data management capabilities, and manufacturer technical support. Future advances in the development of AST systems may increase their clinical impact with the incorporation of molecular techniques that dramatically shorten the time required for results.
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Overview of manual and semiautomated susceptibility testing instrumentation
a Bio-Rad, Hercules, CA, http://bio-rad.com; i2a, Montpellier, France; Mast, Bootle, United Kingdom, http://www.mastascan.com; Oxoid, Basingstoke, United Kingdom, http://www.oxoid.com. See text for other manufacturers.
b Not currently available within the United States.
Overview of manual and semiautomated susceptibility testing instrumentation
a Bio-Rad, Hercules, CA, http://bio-rad.com; i2a, Montpellier, France; Mast, Bootle, United Kingdom, http://www.mastascan.com; Oxoid, Basingstoke, United Kingdom, http://www.oxoid.com. See text for other manufacturers.
b Not currently available within the United States.
Overview of automated broth microdilution susceptibility testing instrumentation a
a neg, negative; ON, overnight; pos, positive; RUO, research use only.
Overview of automated broth microdilution susceptibility testing instrumentation a
a neg, negative; ON, overnight; pos, positive; RUO, research use only.
Unusual resistance phenotypes a
a Resistance phenotypes that are rare or have not yet been detected may represent technical errors.
Unusual resistance phenotypes a
a Resistance phenotypes that are rare or have not yet been detected may represent technical errors.
Gram-negative organisms with expected resistance to commonly tested antimicrobial agents
a Implementation of the revised (2010) cephalosporin and aztreonam CLSI breakpoints for Enterobacteriaceae makes routine ESBL testing unnecessary unless there is consideration of using the agents listed. If ESBL testing is performed and results are positive, the organisms should be reported as resistant to these drugs.
Gram-negative organisms with expected resistance to commonly tested antimicrobial agents
a Implementation of the revised (2010) cephalosporin and aztreonam CLSI breakpoints for Enterobacteriaceae makes routine ESBL testing unnecessary unless there is consideration of using the agents listed. If ESBL testing is performed and results are positive, the organisms should be reported as resistant to these drugs.
Antimicrobial agents that may appear active in vitro but lack clinical efficacy
a Implementation of the revised (2010) cephalosporin and aztreonam CLSI breakpoints for Enterobacteriaceae makes routine ESBL testing unnecessary unless there is consideration of using the agents listed. If ESBL testing is performed and results are positive, the organisms should be reported as resistant to these drugs.
Antimicrobial agents that may appear active in vitro but lack clinical efficacy
a Implementation of the revised (2010) cephalosporin and aztreonam CLSI breakpoints for Enterobacteriaceae makes routine ESBL testing unnecessary unless there is consideration of using the agents listed. If ESBL testing is performed and results are positive, the organisms should be reported as resistant to these drugs.