1292. Activity of Omadacycline and Comparators Against 876 Bacterial Clinical Isolates from Patients with Bone and Joint Infections in the United States and Europe (2015–2022)

BACKGROUND: Omadacycline (OMC) is a third-generation tetracycline class (aminomethylcycline) antibacterial with activity against bacterial isolates expressing common tetracycline, penicillin, fluoroquinolone, macrolide, and vancomycin resistance mechanisms. This study determined the in vitro activity of OMC and comparators against bacterial clinical isolates collected from patients with bone/joint infections (BJI) from the OMC surveillance program (2015–2022). [Figure: see text] METHODS: 876 bacterial isolates from bone/joint infections were received from 39 medical centers in the USA and 16 European countries (2015–2022). Identifications were confirmed by MALDI-TOF MS. The top BJI pathogen was staphylococci (53.4% of all isolates), including S. aureus (47.3%). Other organism groups included streptococci (13.6%), enterococci (7.5%), and Enterobacterales (18.5%). MIC testing of OMC and comparators was conducted according to CLSI M07 (2018) and M100 (2023) guidelines. MIC results were interpreted using FDA or CLSI breakpoints. RESULTS: OMC demonstrated potent in vitro activity against S. aureus (MIC(50/90), 0.12/0.25 mg/L; 98.3% susceptible [S]) isolates from BJI, including MRSA (96.5%S) and coagulase-negative staphylococci (MIC(50/90), 0.12/0.5 mg/L; 96.3%S) (Table). All (100%) S. pyogenes (MIC(50/90), 0.06/0.12 mg/L), 98.4% of Enterococcus spp. (MIC(50/90), 0.12/0.25 mg/L), and 84.9% of other streptococci (MIC(50/90), 0.12/0.25 mg/L) were S to OMC, whereas comparator agent susceptibilities ranged from 20.3% to 57.9%S. Against Gram negatives, ≥90.0% of Acinetobacter spp. (MIC(50/90), 0.5/4 mg/L; 92.3%S), Citrobacter spp. (MIC(50/90), 1/2 mg/L; 92.3%S), E. coli (MIC(50/90), 0.5/2 mg/L; 100%S), Klebsiella spp. (MIC(50/90), 1/4 mg/L; 93.3%S), and S. maltophilia (MIC(50), 2 mg/L; 100%S) isolates were S to OMC (FDA breakpoints applied to similar organism groups for comparison). Comparator agent susceptibilities ranged from 46.2%S to 100%S against these organism groups. CONCLUSION: OMC demonstrated potent in vitro activity against staphylococci, streptococci, enterococci, and Gram-negative isolates from bone/joint infections, with activity generally more potent than or equal to the other tetracycline class comparator agents. DISCLOSURES: Michael D. Huband, BS, BARDA: This study has been funded in part by BARDA under Contract No. 75A50120C00001.|Entasis: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support Michael A. Pfaller, MD, Paratek: Grant/Research Support Kelley Fedler, BS, Melinta: Grant/Research Support|Paratek: Grant/Research Support Helio S. Sader, MD, PhD, FIDSA, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|Cipla: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support Mariana Castanheira, PhD, AbbVie: Grant/Research Support|Basilea: Grant/Research Support|bioMerieux: Grant/Research Support|Cipla: Grant/Research Support|CorMedix: Grant/Research Support|Entasis: Grant/Research Support|Melinta: Grant/Research Support|Paratek: Grant/Research Support|Pfizer: Grant/Research Support|Shionogi: Grant/Research Support