COMPARATIVE SERUM BACTERICIDAL ACTIVITIES OF CEFTIZOXIME AND CEFOTAXIME AGAINST INTERMEDIATELY PENICILLIN-RESISTANT STREPTOCOCCUS-PNEUMONIAE

In a randomized crossover study involving 12 healthy volunteers, 1 g o f ceftizoxime or cefotaxime was administered intravenously every 12 h for a total of three doses on two separate weekends, The duration of s erum bactericidal titers (SBTs) greater than 1:2 and the time serum dr ug concentrations remained above the MIC (T>MIC) were determined again st three clinical isolates of Streptococcus pneumoniae with intermedia te resistance to penicillin. The duration of SBTs and T>MIC for both a ntimicrobial agents exceeded 50% of the dosing interval for all isolat es. Ceftizoxime's T>MIC was statistically greater than that of cefotax ime, indicating that its longer half-life in serum (1.7 h) compared wi th that of cefotaxime (similar to 1 h) compensates for its slightly lo wer microbiologic activity against the penicillin-resistant pneumococc i tested in this study.