The suitability of
ceftriaxone for
penicillin-resistant Streptococcus pneumoniae (PRSP) and
ampicillin-resistant Haemophilus influenzae (especially
beta-lactamase-negative
ampicillin-resistant (BLNAR) H. influenzae) and the relationship between in vitro antimicrobial activities and pharmacokinetic parameters were evaluated. The values for percentage of time above the MIC (%T>MIC) for
ceftriaxone,
cefotiam,
flomoxef,
sulbactam/
cefoperazone,
sulbactam/
ampicillin, and
meropenem, using 400 S. pneumoniae isolates and 430 H. influenzae isolates from patients with community-acquired
pneumonia (CAP) from more than 100 geographically diverse medical centers during January to July of 2005, were calculated by measuring the MIC for each isolate and by using patameters of pharmacokinetics. A broth microdilution method was used to determine the MIC, using the guidelines of the Clinical and Laboratory Standards Institute (CLSI).
Meropenem showed the lowest MIC against
penicillin-susceptible S. pneumoniae, followed by
sulbactam/
cefoperazone and
ceftriaxone.
Ceftriaxone had the best activity against
penicillin-resistant S. pneumoniae and
beta-lactamase-negative and
beta-lactamase-producing
ampicillin-resistant H. influenzae.
Ceftriaxone was unique, showing a long elimination half-life and low MIC values where its serum level duration time was above the MIC for longer than other
cephalosporins. Accordingly, the %T>MIC of
ceftriaxone for a once-daily administration greatly exceeded the efficacy levels of those for the other
antibacterial agents tested.
Ceftriaxone has an excellent balance between in vitro antimicrobial activities and pharmacokinetic profiles; and therefore remains effective as a therapeutic agent against PRSP and BLNAR H. influenzae in CAP.