327. Oritavancin Activity against Staphylococcus aureus Isolates Causing Bone and Joint Infections in European Hospitals (2010–2019)

Background Bone and joint infections (BJI) frequently are caused by Staphylococcus aureus (SA), and since prolonged therapy courses typically are required, agents with convenient administration are preferred. Oritavancin (ORI) is a long-acting lipoglycopeptide approved as a single dose regimen for treating skin and skin structure infections. This study evaluates the activity of ORI and comparators against SA causing BJI in European (EU) hospitals. Methods A total of 575 SA isolates from the SENTRY Antimicrobial Surveillance Program causing BJI in 15 EU countries from 2010 to 2019 were included. Bacterial identification was confirmed by MALDI-TOF MS. Broth microdilution susceptibility (S) testing and interpretation was performed following current CLSI guidelines. The activities of ORI and comparators were evaluated across the years and by EU region: western Europe (W-EU; 491 isolates) and eastern EU/Mediterranean region (E-EU; 84 isolates). Results Methicillin resistance (MRSA) was observed in 20.5% of SA (18.5% in W-EU and 32.1% in E-EU), ranging from 31.1% in 2011 to 14.6% in 2016. MRSA rates were slightly lower in 2016–2019 (14.6%-19.2%) than previous years (2011–2013; 24.4%-31.1%). ORI exhibited 100.0% susceptibility across the entire SA collection with yearly MIC50 and MIC90 variations within 1 doubling dilutions (MIC50 and MIC90, 0.015–0.03 and 0.03–0.06 mg/L, respectively), regardless the MRSA phenotype or EU region. Daptomycin, vancomycin, teicoplanin, and linezolid also showed complete coverage against SA. Clindamycin (CLI; >99.0%S) and levofloxacin (> 95.0%S) were active against methicillin-susceptible SA, but less active against MRSA (67.8%S and 16.1%S, respectively). E-EU MRSA isolates displayed lower S rates than W-EU MRSA isolates to ceftaroline (83.3% vs. 90.6%), CLI (44.4% vs. 74.7%) and tetracycline (66.7% vs. 89.0%), respectively. Conclusion MRSA rates among isolates causing BJI varied within regions. Although several drugs were in vitro active against MSSA, options remained limited against MRSA. ORI showed in vitro activity against the entire collection of European SA isolates and may be a consideration for treating BJI with the convenience of drug administration. Table 1 Disclosures Cecilia G. Carvalhaes, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Cidara Therapeutics (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Fox Chase Chemical Diversity Center (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Merck & Co, Inc. (Research Grant or Support)Pfizer (Research Grant or Support) Jennifer M. Streit, BS, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support) Helio S. Sader, MD, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Melinta (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Paratek Pharma, LLC (Research Grant or Support)Pfizer (Research Grant or Support) Rodrigo E. Mendes, PhD, A. Menarini Industrie Farmaceutiche Riunite S.R.L. (Research Grant or Support)Allergan (Research Grant or Support)Allergan (Research Grant or Support)Basilea Pharmaceutica International, Ltd (Research Grant or Support)Cipla Ltd. (Research Grant or Support)Department of Health and Human Services (Research Grant or Support)GlaxoSmithKline (Research Grant or Support)Melinta Therapeutics, Inc. (Research Grant or Support)Merck (Research Grant or Support)Merck (Research Grant or Support)Pfizer (Research Grant or Support)