Sulfadiazine

The 10 PPCP standards, namely, sulfadiazine (SDZ), sulfamethoxazole (SMZ), tetracycline (TC), oxytetracycline (OTC), ciprofloxacin (CIP), ofloxacin (OFX), erythromycin (ERY), roxithromycin (ROX), ibuprofen (IBU), and NAX, were purchased from Solar-bio (China). Each PPCP was added into the feedwater at 200 ng/L. PPCPs were first dissolved with methanol and then added to the feedwater. The feedwater and PPCPs were prepared daily and mixed thoroughly in the feed tank. PPCPs were detected using the Waters ACQUITY UPLC H-class-Xevo TQ MS triple quadrupole MS/MS spectrometer equipped with an electrospray ionization source (Waters, USA). The detailed detection process was referred to our previous publication^{3 (link)}.

Nine antibiotics were used in the present study. Tetracycline (active ingredient 95.0%, dissolvent: ddH₂O, TET), ampicillin (USP grade, d: 1 mol/L HCl, AMP), ciprofloxacin (a.i. 90.0%, d: 1 mol/L NaOH, CPFX), sulfadiazine (a.i. 98.0%, d: DMSO, SUD), amikacin (a.i. 67.4%, d: ddH₂O, AMI), oxyTetracycline (a.i. 95%, d: 0.1 mol/L HCl, OTC), kanamycin (a.i. 75.0%, d: ddH₂O, KAN) and erythromycin (a.i. 94.1%, d: ddH₂O, EM) were kindly provided by Beijing Solarbio Science & Technology Co., Ltd., Beijing, China; rifampicin (a.i. 98.0%, d: DMSO, RFD) was generously provided by Wuhan Pytbio Bioengineering Co., Ltd., Wuhan, China. The above antibiotics were dissolved and diluted with the corresponding solvents to 50 mg/mL, a stock solution was prepared, and the mixture was stored at 4 °C for subsequent dilution in this study. Additionally, tryptone soybean agar medium (TSA) was used for the isolation and purification of bacteria; nutrient broth agar medium (NA) was used for the propagation of bacteria; 15% glycerol–nutrient broth medium (15% glycerol–NB) was used for the cryopreservation of bacteria; 0.3% agar–NB was used for the determination of bacterial motility; and Luria–Bertani medium (LB) and Luria–Bertani agar medium (LA) were used for the determination of bacterial resistance to antibiotics.