ABSTRACT: Abstract Background Omadacycline (OMC) was FDA approved to treat acute bacterial skin and skin structure infection (ABSSSI) and community-acquired bacterial pneumonia (CABP) for indicated organisms in 2018. Phase 2 OMC clinical trials for uncomplicated urinary tract infection (uUTI; NCT03425396) and acute pyelonephritis (NCT03757234) are ongoing. OMC is active against bacterial isolates expressing common tetracycline, penicillin, fluoroquinolone, and macrolide resistance mechanisms. Methods Isolates (14,000) were collected in 2018 from 31 medical centers located in the United States and 38 medical centers in Europe, including 3,458 staphylococci, 1,551 streptococci, 746 enterococci, 574 Haemophilus spp., and 5,690 Enterobacterales isolates. One isolate per patient infection episode was tested. Identifications were confirmed by MALDI-TOF MS and susceptibility testing was performed using CLSI broth microdilution methods. Results OMC (MIC50/90, 0.12/0.25 mg/L) was highly active against S. aureus isolates from skin and skin structure infection (SSSI; 99.3% susceptible [S]) including MRSA (97.7%S) and MSSA (99.9%S) (table). Similarly, OMC demonstrated potent activity against S. aureus isolates from respiratory tract infection (RTI; MIC50/90, 0.12/0.25 mg/L) including MSSA (98.2%S). All S. lugdunensis isolates from SSSI were S (100.0%) to OMC. All Streptococcus anginosus group (100.0%) and 97.6% of S. pyogenes isolates from SSSI were S to OMC as were 98.0% of S. pneumoniae from RTI. No streptococci were resistant (R) to OMC. OMC (MIC50/90 0.12/0.25 mg/L) had potent activity against E. faecalis isolates from SSSI (99.0%S). OMC S against E. cloacae and K. pneumoniae isolates from SSSI was 92.1% S and 89.4% S, respectively. Similarly, 86.2% of K. pneumoniae isolates from RTI were S to OMC. Susceptibility of H. influenzae isolates from RTI to OMC was 99.8%S (no isolates were R). ?90.0% of E. coli (MIC50/90, 1/2 mg/L) and K. pneumoniae (MIC50/90, 2/4 mg/L) UTI isolates were inhibited by ?4 mg/L of OMC. Conclusion OMC was highly active against bacterial pathogens associated with ABSSSI, CABP, and UTI including staphylococci (97.7%-100.0%S), streptococci (97.6%-100.0%S), E. faecalis (99.0%S). E. cloacae (92.1%S), K. pneumoniae (86.2%-89.4%S), and E. coli. Disclosures All authors: No reported disclosures.
