673. Updated CLSI Ciprofloxacin Breakpoints from a Multicenter Assessment for Enterobacterales, Salmonella spp. and Pseudomonas aeruginosa Using MicroScan Dried Gram Negative MIC Panels

BACKGROUND: Updated US FDA/CLSI ciprofloxacin breakpoints were evaluated against data from a multicenter clinical study with Enterobacterales, Salmonella spp. and P. aeruginosa on a MicroScan Dried Gram-negative MIC (MSDGN) Panel. MIC results were compared to results obtained with frozen broth microdilution panels prepared according to CLSI methodology. METHODS: MSDGN panels were evaluated at three clinical sites by comparing MIC values obtained using the MSDGN panels to MICs utilizing a CLSI broth microdilution reference panel. Data from the combined phases of efficacy and challenge included 803 Enterobacterales, Salmonella spp. and P. aeruginosa clinical isolates tested using the turbidity and Prompt(®) methods of inoculation. To demonstrate reproducibility, a subset of 12 organisms were tested on MSDGN panels at each site during reproducibility. MSDGN panels were incubated at 35 ± 1(º)C and read on the WalkAway System, the autoSCAN-4 instrument, and visually. Read times for the MSDGN panels were at 16-20 hours. Frozen reference panels were prepared and read according to CLSI methodology. FDA and CLSI breakpoints (µg/mL) used for interpretation of MIC results were: Enterobacterales ≤ 0.25 S, 0.5 I, ≥ 1 R; Salmonella spp. ≤ 0.06 S, 0.12-0.5 I, ≥ 1 R; P. aeruginosa ≤ 0.5 S, 1 I, ≥ 2 R. RESULTS: Essential and categorical agreement was calculated compared to frozen reference panel results. Results for isolates tested during efficacy and challenge with Prompt inoculation and manual read are as follows: CONCLUSION: Ciprofloxacin MIC results for Enterobacterales, Salmonella spp., and P. aeruginosa obtained with the MSDGN panel correlate well with MICs obtained using frozen reference panels using updated FDA/CLSI interpretive criteria in this multicenter study. * PROMPT(®) is a registered trademark of 3M Company, St. Paul, MN USA. BEC, the stylized logo and the BEC product and service marks mentioned herein are trademarks or registered trademarks of Beckman Coulter, Inc. in the US and other countries. DISCLOSURES: Maria M. Traczewski, BS MT (ASCP), Beckman Coulter (Scientific Research Study Investigator) Denise Beasley, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Amanda Harrington, PhD, Beckman Coulter (Scientific Research Study Investigator) Sharon DesJarlais, BS, Beckman Coulter (Other Financial or Material Support, Research personnel) Omai Garner, PhD, D(ABMM), Beckman Coulter (Scientific Research Study Investigator) Christine Hastey, PhD, Beckman Coulter (Employee) Regina Brookman, BS, Beckman Coulter (Employee) Zabrina Lockett, MS, Beckman Coulter (Employee) Jennifer Chau, PhD, Beckman Coulter (Employee)