697. Evaluation of Contezolid Activity to Anaerobic and Gram-positive-cocci Isolates from a Phase 3 Acute Bacterial Skin and Skin Structure Infection Clinical Trial (MRX-I-06)

Background Contezolid (MRX-I) is an oxazolidinone in development for the treatment of acute bacterial skin and skin structure infections (ABSSSIs). In this study, in vitro susceptibility (S) for Contezolid and comparator agents for Gram-positive (GP) and anaerobic isolates from Phase 3 ABSSSI clinical trials were determined. Methods 313 isolates were collected from 65 participated sites and sent to a central laboratory for MIC testing. Clinical isolates included 34 anaerobes (15 Finegoldia magna, 8 Actinomyces spp., 4 Prevotella spp., 3 Propionibacterium avidum, 2 Peptostreptococcus spp., 1 Veillonella spp. and 1 Bacteroides fragilis), 187 S. aureus (59. 7%). 12 S. pyogenes, 5 Enterococcus and 75 other Gram-positive organisms. Broth micro-dilution method was used to determine the MIC of contezolid, linezolid and other comparators to facultative isolates. Agar dilution was carried out for the anaerobes. Results For both 33 MRSA and 154 MSSA MIC50/90 values of contezolid and linezolid were 2 mg/L. One E. faecalis showed decreased susceptibility to oxazolidinones (both MIC = 4). 1 mg/L contezolid and linezolid could inhibit 12 S. pyogenes. 2 mg/L contezolid and linezolid could inhibit 15 Finegoldia magna. 0.5 mg/L contezolid and linezolid could inhibit 8 Actinomyces spp. To one Bacteroides fragili, two Prevotella bivia and one Leuconostoc lactis (Intrinsic resistant to vancomycin) the MIC of contezolid were 4 or 8 mg/L. In general, Contezolid had lower or equal MIC50/90 values against both GP and ANA species compared with linezolid for all organisms. Conclusion Contezolid demonstrated potent in vitro antibacterial activity against Gram-positive and anaerobic isolates tested. These data suggest that contezolid might be a beneficial supplement to the arena against MDR Gram-positive infection. Disclosures All authors: No reported disclosures.