Table 2.

Determination of the MIC and MBC of each β-lactam antibiotic for the Amoxs and Amoxrstrainsa

β-LactamMIC (μg/ml) for strainMBC (μg/ml) for strain
AmoxsAmoxrAmoxsAmoxr
Amoxicillin0.03–0.064–80.125–0.54–8
Ampicillin0.03–0.064–80.03–0.064–8
Penicillin G0.03–0.064–80.03–0.068–16
Oxacillin2–431–624–862–125
Mezlocillin0.125–0.254–80.25–1.04–16
Cefuroxime0.03–0.062–40.06–0.54–8
Ceftriaxone0.125–0.254–80.125–1.08–16
Aztreonam4–816–314–862–125
  • a MICs of each β-lactam were determined after 24 to 48 h of incubation at 37°C using a broth microdilution method (7); MBCs were determined by examination of agar plate subcultures after 72 h of incubation at 37°C (7). Data shown are the averages of three separate experiments.