Background: Eravacycline (XERAVA™) is a fluorocycline antibiotic developed by Tetraphase Pharmaceuticals Inc. for the treatment of complicated intra-abdominal infections. This study evaluated the performance of ETEST® Eravacycline (ERV), a new gradient diffusion strip, for determining the minimum inhibitory concentration (MIC) of Enterobacteriaceae, Enterococcus faecalis and Enterococcus faecium as compared to CLSI/ISO-20776-2 broth microdilution reference method (BMD).
Material/Methods: A set of 679 isolates including 542 Enterobacteriaceae and 137 Enterococci were tested at 4 clinical trial sites using ETEST® ERV and BMD. Results were analyzed for essential (EA) and category (CA) agreements, major (ME) and very major (VME) error rates using EUCAST breakpoints [E. coli: ≤ 0.5 (S), > 0.5 (R) mg/L, Enterococcus spp.: ≤ 0.125 (S), > 0.125 (R) mg/L) as well as FDA breakpoints (Enterobacteriaceae: ≤ 0.5 mg/L (S), Enterococcus faecium and Enterococcus faecalis: ≤ 0.064 mg/L (S)]. Results for Klebsiella pneumoniae were analyzed for EA only for EU claim as EUCAST breakpoints have not been established.
Results: Results are summarized in the table below. ETEST® ERV performance for Enterobacteriaceae and Enterococcus spp. met FDA and ISO acceptance criteria for EA (≥ 90%), CA (≥ 90%), ME (≤ 3%) and VME (≤ 2 or ≤ 3% respectively). A trend to overestimate E. coli, C. freundii and K. aerogenes MICs was observed.
Conclusions: Results of this study support the accuracy of ETEST® ERV for determining MICs of Enterobacteriaceae, and Enterococcus spp. As such, the ETEST® ERV is considered as substantially equivalent to BMD.
*In accordance with the FDA response to Susceptibility Testing Manufacturers Association (STMA) letter dated November 3, 2015, for drugs for which there is no intermediate breakpoint, the VME rate and/or the ME rate may be adjusted to exclude the VME results and/or the ME results that were within essential agreement (EA).