Eravacycline activity against clinical S. aureus isolates from China: In vitro activity, MLST profiles and heteroresistance

Abstract

Background: Mortality rates for patients with Staphylococcus aureus (S. aureus) infections have improved only modestly in recent decades and S. aureus infections remain a major clinical challenge This study investigated the in vitro antimicrobial activity of erevacycline (erava) against clinical S. aureus isolates from China, as well as the heteroresistance frequency of erava and sequence types (STs) represented in the sample. Results: A sample of 328 non-duplicate clinical S. aureus isolates, including 138 methecillin-resistant (MRSA) and 190 methecillin-sensitive (MSSA) isolates, were collected retrospectively in China. Erava exhibited excellent in vitro activity (MIC 50 ≤ 0.25 mg/L) against MRSA and MSSA, including isolates harboring Tet specific resistance genes. The frequency of erava heteroresistance in MSSA with erava MICs = 0.5 mg/L was 13.79% (4/29); no MRSA with erava MICs ≤0.5 mg/L exhibited heteroresistance. Heteroresistance- derived clones had no 30S ribosome subunit mutations, but their erava MICs (range, 1-4 mg/L) were suppressed dramatically in the presence of efflux protein inhibitors. Conclusions: Conclusively, erava exhibited excellent in vitro activity against S. aureus, however hints of erava heteroresistance risk and MIC creep were detected, particularly among MSSA with MICs of 0.5 mg/L.