ECCMID 2020 Scientific Poster: Cephalexin MIC Results for Enterobacterales


A multicenter study was performed to evaluate the accuracy of cephalexin on a MicroScan Dried Gram-negative MIC (MSDGN) Panel when compared to a frozen ISO/CLSI broth microdilution reference panel.


An evaluation was conducted at three U.S. sites by comparing MIC values obtained using the MSDGN to MICs utilizing an ISO/CLSI broth microdilution reference panel. A total of 450 Enterobacterales clinical isolates were tested using the turbidity and Prompt® methods of inoculation during the efficacy phase. A subset of 12 organisms was tested on MSDGN panels at each site during reproducibility. MSDGN panels were incubated at 35 ± 1ºC and read on the MicroScan WalkAway system, the MicroScan autoSCAN-4 instrument, and read visually. Read times for the MSDGN panels were at 16-20 hours. Frozen reference panels were prepared according to ISO/CLSI methodology, incubated for 16-20 hours and read visually. All frozen reference panels were incubated at 35 ± 2ºC for 16-20 hours and read visually. EUCAST breakpoints (mg/L) used for interpretation of MIC results were: Enterobacterales ≤ 16 S, > 16 R.


Essential and categorical agreement when compared to frozen reference panel results, for all isolates tested in efficacy as follows:


Read Method

Essential Agreement %

Categorical Agreement %

Very Major Error (VMJ)* %

Major Error (MAJ)* %

WalkAway 98.0 (441/450) 98.4 (443/450) 96.7 (435/450) 97.3 (438/450) 0.0 (0/188) 0.0 (0/188)) 1.5 (4/262) 0.8 (2/262)
autoSCAN-4 97.8 (440/450) 98.7 (744/450) 96.9 (436/450) 98.2 (442/450) 0.0 (0/188) 0.0 (0/188) 1.5 (4/262) 0.0 (0/262)
Visually 98.0 (441/450) 98.7 (744/450) 97.1 (437/450) 98.0 (441/450) 0.0 (0/188) 0.0 (0/188) 1.5 (4/262) 0.4 (1/262)

T = Turbidity inoculation method, P = Prompt inoculation method

*Calculation of MAJ and VMJ excluding 1 well errors


This multicenter study showed that cephalexin MIC results for Enterobacterales obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using EUCAST interpretive criteria.
MIC panel scientific poster

Poster Multicenter Evaluation of Cephalexin MIC Results for Enterobacterales

Download the ECCMID 2020 poster for complete information demonstrating that cephalexin MIC results for Enterobacteriales correlate well with the MICs obtained using frozen reference panels. Review details from this multicenter study which used EUCAST interpretive criteria.


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O.B. Garner, UCLA David Geffen School of Medicine, Los Angeles, CA,  C. Emery, Indiana University School of Medicine, Indianapolis, IN, A. Harrington, Loyola University Medical Center, Maywood, IL, S. DesJarlais, Loyola University Medical Center, Maywood, IL, C. J. Hastey, Beckman Coulter Microbiology, West Sacramento, CA,  R.K. Brookman, Beckman Coulter Microbiology, West Sacramento, CA, Z.C. Lockett4, and J.Y. Chau, Beckman Coulter Microbiology, West Sacramento, CA
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