Lack of Synergy of Erythromycin Combined with Penicillin or Cefotaxime against Streptococcus pneumoniae In Vitro

Abstract
We investigated a possible synergistic effect of a macrolide and β-lactams against Streptococcus pneumoniae strains with different resistance profiles. Checkerboard and time-kill assays of erythromycin combined with penicillin or cefotaxime essentially showed indifference, suggesting that these antibiotics in combinations in vitro act substantially as individuals in their activity against S. pneumoniae .