646. Activity of Oritavancin and Comparator Agents Against Coagulase-negative Staphylococci Causing Bloodstream Infections in US Medical Centers (2017-2019)

BACKGROUND: Coagulase-negative staphylococci (CoNS) is a common organism group implicated in catheter-related bloodstream infection (BSI) and infective endocarditis. Prompt appropriate antimicrobial therapy is crucial for suspected or confirmed invasive infections. The in vitro activity of oritavancin (ORI) and comparators was evaluated against CoNS causing BSI in US medical centers. [Figure: see text] METHODS: 587 CoNS isolates (1/patient) were consecutively collected in 30 US centers in 2017-2019. Bacterial identification was performed by MALDI-TOF, and susceptibility testing using CLSI broth microdilution methodology in a central laboratory. CLSI breakpoints were applied for comparators and the ORI susceptible (S) breakpoint for S. aureus (≤0.12 mg/L) was used for in vitro comparison only. RESULTS: The most common species were S. epidermidis (Sepi; 62.4%; 366), followed by S. hominis (Shom; 13.1%; 77), S. capitis (Scap; 7.3%; 43), S. lugdunensis (Slug; 5.1%; 30), and S. haemolyticus (Shae; 4.3%; 25). 12 other species represented < 10 (1.5%) isolates each. Overall, 59.1% of isolates were methicillin-resistant (MR), with the highest rate in Sepi (73.2%), followed by Shae (68.0%), Shom (46.8%), and Scap (30.2%). No MR isolates were detected in Slug. ORI (MIC(50/90), 0.06/0.12 mg/L) inhibited 96.1% of CoNS at ≤0.12 mg/L. Linezolid (LZD; MIC(50/90), 1/1 mg/L; 96.4%S), daptomycin (DAP; MIC(50/90), 0.25/0.5 mg/L; 100%S), and vancomycin (VAN; MIC(50/90), 1/2 mg/L; 100%S) were also active against CoNS. ORI displayed similar MIC(50) (0.03-0.06 mg/L) and MIC(90) (0.12-0.25 mg/L) values against Sepi, Shom, Scap, and Shae, and inhibited 96.0%, 96.1%, 97.7%, and 84.0% of these isolates at ≤0.12 mg/L, respectively. All Slug isolates were inhibited by ORI at ≤0.015 mg/L. ORI inhibited 94.8% of all MRCoNS at ≤0.12 mg/L, and 95.5%, 94.4%, 92.3%, and 82.4% of MR Sepi, Shom, Scap, and Shae species, respectively. VAN, DAP, and LZD inhibited 100.0%, 100.0%, and 93.9% of MRCoNS isolates at their susceptible breakpoints, respectively. CONCLUSION: ORI was highly active and inhibited ≥96% of all CoNS and individual species ( >10 isolates) at ≤0.12 mg/L, regardless of methicillin profile, except for Shae. VAN, DAP, and LZD were also active against CoNS causing BSI in US medical centres. DISCLOSURES: Cecilia G. Carvalhaes, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Pfizer: Grant/Research Support Helio S. Sader, MD, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Pfizer: Grant/Research Support Jennifer M. Streit, BS, MT(ASCP), Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Shionogi: Grant/Research Support Rodrigo E. Mendes, PhD, AbbVie: Grant/Research Support|Cidara: Grant/Research Support|GSK: Grant/Research Support|Melinta: Grant/Research Support|Nabriva Therapeutics: Grant/Research Support|Office for Assistant Secretary of Defense for Health Affairs: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support|Spero Therapeutics: Grant/Research Support.