In vitro activity of cefprozil (BMY 28100) and cefepime (BMY 28142) against Streptococcus pneumoniae, Branhamella catarrhalis, and Haemophilus influenzae, and provisional interpretive criteria for disk diffusion and dilution susceptibility tests with Haemophilus influenzae.

The in vitro activities of two new cephalosporins, an oral agent, cefprozil and a parenteral compound, cefepime, were assessed against recent clinical isolates of Streptococcus pneumoniae, Moraxella (Branhamella) catarrhalis, and Haemophilus influenzae. In general, both cefprozil and cefepime MICs were higher for beta-lactamase-producing strains of M. catarrhalis in comparison to strains that lacked beta-lactamase. By contrast, beta-lactamase-positive and -negative strains of H. influenzae had similar cefprozil and cefepime minimum inhibitory concentrations (MICs). The MIC90 values for cefprozil were 0.12, 32, 4.0, and 0.5 micrograms/ml versus S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis, respectively. In comparison to three other oral cephalosporins included in this study, cefaclor, cefuroxime axetil, and cefixime, cefprozil was the most active agent against S. pneumoniae, the least active against B. catarrhalis, and equivalent in activity to cefaclor against H. influenzae. The cefepime MIC values against S. pneumoniae, H. influenzae, and beta-lactamase-positive and negative strains of M. catarrhalis were 0.03, 0.25, 2.0, and 0.5 micrograms/ml, respectively. Cefepime was less active than ceftriaxone for all three organism groups, however, was in all cases more active than cefixime, cefuroxime, cefaclor, and cefprozil.(ABSTRACT TRUNCATED AT 250 WORDS)