Methods: 11,020 multidrug-resistant clinical isolates corresponding to more than 485,000 data points were used to compare the three major identification and antibiotic susceptibility testing (AST) platforms. Bacterial suspensions, prepared from a single plate, were simultaneously tested on all platforms in the same laboratory. Discrepancies were derived from minimum inhibitory concentration values using 2014 interpretive guidelines. Molecular methods and manual microbroth dilution were reference standards.
Results: Most discrepancies were due to drug-organism-AST platform combination instead of individual factors. MicroScan mis-identified Acinetobacter baumannii (p<0.001) and underestimated carbapenem susceptibility in Klebsiella pneumoniae. Vitek-2 and Phoenix had higher discrepancies for blaKPC-containing Enterobacteriaceae (P<0.05), and reported false-susceptibilities more often.
Conclusion: While all platforms performed according to standards, each had strengths and weaknesses for organism identification, assaying specific drug-organism combinations, and inferring carbapenemase production.
Y. Kwak, None
L. Preston, None
R. Rabinowitz, None
M. Hinkle, None
P. Waterman, None
E. Lesho, None