Methods: A total of 15,882 US clinical isolates were collected from 82 sites located in 37 states. Isolates were principally from cSSSI (51.1%), pneumonia in hospitalized patients (27.6%), and bloodstream infections (14.4%). Isolates were tested for S by CLSI methods, and MIC interpretations used CLSI criteria. Methicillin-resistant SA (MRSA) resistant to ≥3 additional drug classes were considered multidrug-resistant (MDR). The drugs used to assess MDR status were: clindamycin (CLI), daptomycin (DAP), erythromycin (ERY), gentamicin (GEN), levofloxacin (LEVO), linezolid (LZD), tetracycline (TET), and trimethoprim-sulfamethoxazole (TMP-SMX).
Results: All SA were S to TLV at the current CLSI breakpoint (≤0.12 µg/mL), and all TLV MIC90 values were 0.03-0.06 µg/mL, regardless of year, census division, or MDR phenotype. TLV MIC50/90 values (0.03/0.06 µg/mL) were at least 8-fold lower than corresponding values for DAP (0.25/0.5 µg/mL), LZD (1/1 µg/mL), and vancomycin (VAN; 0.5/1 µg/mL) against SA. No VAN-resistant SA isolates were detected. Overall S rates were: CLI (84.4%), DAP (99.9%), ERY (41.3%), GEN (97.6%), LEVO (62.1%), LZD (>99.9%), TET (95.5%), and TMP-SMX (98.2%), and no significant changes were observed over the 3 years. MRSA rates declined overall (from 46.8% to 43.6%). MDR MRSA increased from 27.3% (2014) to 30.2% (2016). The TLV MIC50 value for DAP-nonsusceptible and LZD-R isolates was 0.06 µg/mL; the TLV MIC90 value for isolates with elevated VAN MICs (2 µg/mL; 0.4% of all SA) was 0.12 µg/mL.
Conclusion: TLV exhibited potent in vitro activity against SA (including MDR) from all US census divisions, with MIC50/90 values at least 8-fold more potent than comparator values. Resistance rates for most comparators remained steady, the MRSA rate fell, and the MDR MRSA rate increased during the study period.
L. R. Duncan,
Theravance Biopharma US, Inc.:
R. E. Mendes, Theravance Biopharma US, Inc.: Research Contractor , Research grant