[Relationship between protein binding and antimicrobial activities of antibiotics against Streptococcus pneumoniae and Haemophilus influenzae].

Fifty isolates of Streptococcus pneumoniae and 42 isolates of Haemophilus influenzae were isolated from the blood of children admitted to pediatric wards of hospitals in subprefucture between January 1998 and December 2005. The susceptibilities were measured by a microbroth dilution method using a standard broth and a broth containing 4.5% albumin. Against S. pneumoniae, penicillin G, ampicillin, cefotaxime, ceftriaxone, panipenem, meropenem, vancomycin, cefditoren, cefcapene, cefteram, faropenem and tebipenem were used and against H. influenzae, ampicillin, piperacillin, cefotaxime, ceftriaxone, panipenem, meropenem, clavulanic acid/ amoxicillin, cefditoren, cefcapene, cefteram, faropenem and tebipenem were used. Against S. pneumoniae, tebipenem was the highest antimicrobial activity in oral antibiotics (MIC90; < or = 0.06 microg/ml) and panipenem showed the highest activity for intravenous antibiotics (MIC90; < or = 0.12 microg/ml). Against H. influenzae, cefditoren was the highest activity for oral antibiotics (MIC90; < or = 0.06 microg/ml) and meropenem showed the highest activity for intravenous antibiotics (MIC90; < or = 50.06 microg/ml). The MIC90s measured by albumin containing broth were higher than those measured by standard broth. Protein binding rates of ceftriaxone, cefditoren, and faropenem were greater than 90%, and the MIC90 of these antibiotics measured by albumin addition methods were over 4-fold higher than those measured by standard methods.