Streptococcus pneumoniae

In a randomized crossover study involving 12 healthy volunteers, 1 g of ceftizoxime or cefotaxime was administered intravenously every 12 h for a total of three doses on two separate weekends. The duration of serum bactericidal titers (SBTs) greater than 1:2 and the time serum drug concentrations remained above the MIC (T>MIC) were determined against three clinical isolates of Streptococcus pneumoniae with intermediate resistance to penicillin. The duration of SBTs and T>MIC for both antimicrobial agents exceeded 50 % of the dosing interval for all isolates. Ceftizoxime’s T>MIC was statistically greater than that of cefotaxime, indi-cating that its longer half-life in serum (1.7 h) compared with that of cefotaxime (;1 h) compensates for its slightly lower microbiologic activity against the penicillin-resistant pneumococci tested in this study. The emergence of penicillin-resistant Streptococcus pneu-moniae (PRSP) has been an international problem, but in the United States, it has become a significant problem only within the past 5 years (6). According to the most recent National Committee for Clinical Laboratory Standards (NCCLS) guide-lines, S. pneumoniae is considered to exhibit low-level (inter-mediate) or high-level resistance to penicillin if the MIC is 0.1