Levofloxacin

AF and antibiotics [fosfomycin (FOF); ciprofloxacin (CIP); tetracycline (TET); linezolid (LZD); chloramphenicol (CHL); levofloxacin (LVX); teicoplanin (TEC); clindamycin hydrochloride (CLI) hydro; gentamicin (GEN); vancomycin (VAN)] were purchased from the MedChemExpress company (Monmouth Junction, NJ, United States). E. faecalis ATCC 29212, S. aureus ATCC25923 and ATCC29213 were kindly provided by Juncai Luo (Tiandiren Biotech, Changsha, China). S. epidermidis RP62A and ATCC 12228 were given by Di Qu (Shanghai Medical College of Fudan University), S. aureus ATCC43300 (MRSA), Newman, and RJ-2 were given by Min Li (Renji Hospital, Shanghai Jiao Tong University School of Medicine). Other clinical strains were isolated from the wound secretion or sputum of inpatients at the Third Xiangya Hospital of Central South University. Staphylococcus spp. were grown in tryptic soy broth (TSB) broth medium (Solarbio, Shanghai, China), and E. faecalis was grown in brain heart infusion (BHI) broth medium (Solarbio, Shanghai, China) at 37°C.

Susceptibility testing was performed for each included strain in a broth microdilution after EUCAST (European Committee on Antimicrobial Susceptibility Testing) guidelines, determining the MIC of gepotidacin towards each strain. Additionally, MICs of 100 strains towards levofloxacin and moxifloxacin were assessed in a broth microdilution. The anti-infective agents were diluted in solvent (dimethyl sulfoxide, DMSO) and Mueller Hinton Bouillon 2 for the preparation of stock solutions. Working solutions were prepared by dilution in Mueller Hinton Bouillon 2 and all solutions were stored at −20°C. Broth microdilution with gepotidacin, levofloxacin and moxifloxacin (MedChemExpress LLC, Monmouth, NJ, USA) was performed in concentrations between 0.03 and 16 mg/L. Additionally, MIC strip tests (Liofilchem srl, Roseto degli Abruzzi, Italy) were performed for co-trimoxazole for a total of 100 strains.