Atcc19411

The T. pyogenes strain ATCC19411 was obtained from the American Type Culture Collection (Manassas, VA, USA). The T. pyogenes strains (BM07-1, BMH06-3, and T001-T017) were isolated from dairy cattle and preserved in our laboratory. The resistance phenotypes of T. pyogenes and the minimum inhibitory concentrations (MICs) of luteolin against T. pyogenes are shown in Table S1 [24 (link),32 (link)]. T. pyogenes strains were maintained on Mueller-Hinton Agar (MHA, Solarbio, Beijing, China) supplemented with 5% (v/v) sheep blood (Hopebio, Qingdao, China) under microaerophilic conditions (5% CO₂) at 37 °C for 36 h. The resulting colonies were inoculated in nutrient broth (NB, Solarbio) supplemented with 8% (v/v) fetal bovine serum (FBS, Gibco, Grand Island, NE, USA). Luteolin was obtained from Pureone Biotechnology Co., Ltd. (Shanghai, China) and dissolved in 1% dimethyl sulfoxide (DMSO, Sigma-Aldrich, Shanghai, China) to prepare a stock solution.

T. pyogenes strain ATCC19411 was obtained from the American Type Culture Collection (Manassas, United States). T. pyogenes isolates (n = 19) were collected from dairy cows in Inner Mongolia and Liaoning, China and identified by 16S rRNA gene sequencing (Zhang et al., 2017 (link); Guo et al., 2020 (link)). T. pyogenes strains were cultured on Mueller-Hinton agar (MHA; Solarbio, Beijing, China) containing 5% (v/v) defibrinated sheep blood (Hopebio, Qingdao, China) in an incubator (5% CO₂; Thermo Fisher, Shanghai, China) at 37°C for 36 h, and the colonies were inoculated in brain heart infusion (BHI) medium (Solarbio, Beijing, China) supplemented with 8% (v/v) fetal bovine serum (FBS; Gibco, Grand Island, United States). E. coli strains BL21 (DE3) (TransGen Biotech, Beijing, China) and Trans-1-T1 (TransGen Biotech, Beijing, China) were cultured in Luria-Bertani (LB) broth (Solarbio, Beijing, China) in a shaker at 200 rpm or on LB agar plates supplemented with kanamycin (50 μg/mL; Sigma, Shanghai, China) at 37°C.