Bactericidal activity of levofloxacin and cefcapene against Haemophilus influenzae

Abstract

Bactericidal activity of levofloxacin was compared to that of cefcapene against Haemophilus influenzae isolated in 1998. Levofloxacin and cefcapene were bactericidal against ampicillin-susceptible strain at a concentration of 1 and 4 times the MIC, but only levofloxacin was bactericidalagainst β-lactamasenegative and ampicillin-resistant H. influenzae luenzae (BLNAR). Significant morphological alteration was not observed after levofloxacin treatment, while filamentous cells appeared after cefcapene treatment of the ampicillin-susceptible strain. BLNAR changed to filamentous without drug exposure, so we analyzed the amino acid sequence of the gene encoding penicillin-binding protein (PBP) 3. We found 6 substitutions in PBP 3, suggesting that PBP 3 alteration was a cause of the lack of bactericidal activity of cefcapene.