Surveillance of Omadacycline Activity Tested against Clinical Isolates from the United States and Europe: Report from the SENTRY Antimicrobial Surveillance Program, 2016 to 2018

Omadacycline is a broad-spectrum aminomethylcycline approved in October 2018 by the U.S. Food and Drug Administration for treating acute bacterial skin and skin structure infections and community-acquired pneumonia as both an oral and intravenous once-daily formulation. In this report, the activities of omadacycline and comparators were tested against 49,000 nonduplicate bacterial isolates collected prospectively during 2016 to 2018 from medical centers in Europe (24,500 isolates, 40 medical centers [19 countries]) and the United States (24,500 isolates, 33 medical centers [23 states and all 9 U.S. census divisions]). Omadacycline was tested by broth microdilution following the methods in Clinical and Laboratory Standards Institute document M07 ( Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard , 11th ed., 2018). Omadacycline (MIC 50/90 , 0.12/0.25 mg/liter) inhibited 98.6% of Staphylococcus aureus isolates at ≤0.5 mg/liter, including 96.3% of methicillin-resistant S. aureus isolates and 99.8% of methicillin-susceptible S. aureus isolates. Omadacycline potency was comparable for Streptococcus pneumoniae (MIC 50/90 , 0.06/0.12 mg/liter), viridans group streptococci (MIC 50/90 , 0.06/0.12 mg/liter), and beta-hemolytic streptococci (MIC 50/90 , 0.12/0.25 mg/liter), regardless of species and susceptibility to penicillin, macrolides, or tetracycline. Omadacycline was active against all Enterobacterales tested (MIC 50/90 , 1/8 mg/liter; 87.5% of isolates were inhibited at ≤4 mg/liter) except Proteus mirabilis (MIC 50/90 , 16/>32 mg/liter) and indole-positive Proteus spp. (MIC 50/90 , 8/32 mg/liter) and was most active against Escherichia coli (MIC 50/90 , 0.5/2 mg/liter), Klebsiella oxytoca (MIC 50/90 , 1/2 mg/liter), and Citrobacter spp. (MIC 50/90 , 1/4 mg/liter). Omadacycline inhibited 92.4% of Enterobacter cloacae species complex and 88.5% of Klebsiella pneumoniae isolates at ≤4 mg/liter. Omadacycline was active against Haemophilus influenzae (MIC 50/90 , 0.5/1 mg/liter), regardless of β-lactamase status, and against Moraxella catarrhalis (MIC 50/90 , ≤0.12/0.25 mg/liter). The potent activity of omadacycline against Gram-positive and -negative bacteria indicates that omadacycline merits further study in serious infections in which multidrug resistance and mixed Gram-positive and Gram-negative bacterial infections may be a concern.