In vitro bactericidal activity of ABT-773 and amoxicillin against erythromycin-susceptible and -resistant strains of Streptococcus pyogenes.

The bactericidal activity of ABT-773 was compared with amoxicillin against 10 clinical isolates of S. pyogenes (six erythromycin susceptible and four erythromycin resistant). The MIC ranges (mg/L) were 0.004-0.25 of ABT-773 and 0.015-0.12 of amoxicillin. At 24 h, ABT-773 concentrations of 2 x MIC and 8 x MIC were bactericidal against three and six organisms, respectively. In comparison, amoxicillin was bactericidal against all 10 organisms at both test concentrations.