Amoxicillin trihydrate

Cells were treated with lascufloxacin hydrochloride (MIC of 0.031 μg/mL for M1 and 0.016 μg/mL for strain #2; Kyorin Pharmaceutical Co., Ltd., Tokyo, Japan) and amoxicillin trihydrate (MIC of 0.016 μg/mL for both strains; FUJIFILM Wako Pure Chemical Corporation, Osaka, Japan). MICs of each agents were determined according to the standard microdilution assay [21] .

The following antimicrobial agents were used: cefmetazole (sodium salt, Sigma-Aldrich Japan); clindamycin phosphate (MP Bio Japan, Tokyo, Japan); ofloxacin (LKT Laboratories, St. Paul, MN, USA); and amoxicillin trihydrate, azithromycin, clarithromycin, ciprofloxacin hydrochloride monohydrate, and cefcapene pivoxil hydrochloride hydrate (all from Wako Pure Chemical Industries, Osaka, Japan). Stock solutions were made by dissolving each antibiotic in purified water or ethanol; 4-fold serial dilutions of each stock were prepared, and each solution was filter-sterilized (pore size, 0.22 μm; Millipore, Bedford, MA, USA). Solutions were added to blood agar to yield final antibiotic concentrations of from 32 to 0.0019 μg/ml.