In vitro activities of cefotaxime, ceftriaxone, ceftazidime, cefpirome, and penicillin against Streptococcus pneumoniae isolates.

The in vitro activities of four extended-spectrum cephalosporins and benzyl penicillin were evaluated against 698 clinical isolates of Streptococcus pneumoniae, including 130 (19%) penicillin-intermediate and 84 (12%) penicillin-resistant strains. Cefotaxime and ceftriaxone were essentially identical in their antipneumococcal activities: both were active against penicillin-susceptible strains and most penicillin-intermediate strains. Cefpirome was twice as potent as cefotaxime and ceftriaxone against penicillin-resistant strains. Ceftazidime was 8- to 16-fold less active than cefotaxime and ceftriaxone against S. pneumoniae in vitro, and thus, its spectrum included only penicillin-susceptible strains.