644. Comparative Evaluation of ETEST® ERV bioMérieux with the CLSI Broth Microdilution Method for Eravacycline MIC Determination

Background Eravacycline (XERAVA™) is a novel, FDA and EMA-approved fully-synthetic fluorocycline antibiotic developed by Tetraphase Pharmaceuticals Inc. for the treatment of complicated intra-abdominal infections (cIAI) including those caused by multidrug-resistant (MDR) pathogens that have been highlighted as urgent public health threats by the US CDC and the WHO. The new ETEST ERV strip (MIC range 0.002 – 32 µg/mL) has been developed by bioMérieux and calibrated vs. the broth microdilution reference method (BMD) as described by the Clinical and Laboratory Standards Institute (CLSI) to determine the minimal inhibitory concentration (MIC) of eravacycline against Enterobacterales and Enterococci. The aim of the study was to compare ETEST ERV to the CLSI BMD method on a panel of 166 strains comprising 131 Enterobacterales and 35 Enterococci. Methods Quality control was performed with the CLSI QC strains E.coli ATCC 25922 and E.faecalis ATCC 29212. The ETEST ERV strip was applied on a Mueller–Hinton agar plate previously seeded with a 0.5 McF bacterial suspension. After incubation for 16–20H at 35°C, the reading was performed using the bacteriostatic mode i.e.,80% of growth. The FDA-approved breakpoints were applied (S≤0.5µg/mL for Enterobacterales and S ≤0.064 µg/mL for Enterococci). Results The MIC essential agreement was 99.4% at ±1 dilution for the whole panel and the category agreement was 96.4% with 4.8% Major Errors (1 E. coli, 2 K. pneumoniae, 1 K.aerogenes, 1 C. koseri, 1 E. faecalis), all at ±1 dilution around the single breakpoint. No Very Major Error (VME) was observed. Conclusion In this study, the new ETEST ERV strip has been found to be substantially equivalent to the CLI reference method. MIC end-points appear easier to read in comparison to the reference method. With a 15-dilution MIC range and simplicity of use, ETEST ERV could represent a valuable tool for MIC determination and an alternative to the BMD reference method. ETEST ERV will undergo clinical studies to seek IVD FDA clearance and CE marking. For Research Use Only. The performance characteristics of this product have not yet been established. Disclosures All authors: No reported disclosures.