1595. An 11,000 Isolate Same Plate/Same Day Comparison Reveals Notable Differences Among the Three Most Widely Used Platforms for Analyzing Multidrug-resistant Clinical Pathogens
Session: Poster Abstract Session: Diagnostics for Multidrug-Resistant Bacteria
Saturday, October 10, 2015
Room: Poster Hall
Background: Stewardship of the dwindling number of effective antibiotics relies on accurate phenotyping. We sought to conduct the first large scale, same plate and day comparison of the three most widely-used bacterial analyzers.

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.

Lindsey Nielsen, PhD1, Robert Clifford, Ph.D.1, Yoon Kwak, MS1, Lan Preston, AS1, Ronald Rabinowitz, MD2, Mary Hinkle, M.D.1, Paige Waterman, M.D.3 and Emil Lesho, D.O., FIDSA1, (1)Walter Reed Army Institute of Research, Silver Spring, MD, (2)University of Maryland Shock Trauma Center, Baltimore, MD, (3)GEIS, Armed Forces Health Surveillance Center, Silver Spring, MD

Disclosures:

L. Nielsen, None

R. Clifford, None

Y. Kwak, None

L. Preston, None

R. Rabinowitz, None

M. Hinkle, None

P. Waterman, None

E. Lesho, None

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