INVITRO 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-mu-g/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-mu-g/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. The following susceptibility test interpretive criteria are proposed for use when testing H. influenzae against cefprozil and cefepime using Haemophilus test medium (HTM): cefprozil: greater-than-or-equal-to 15 mm (less-than-or-equal-to 8.0-mu-g/ml) = susceptible and less-than-or-equal-to 14 mm (greater-than-or-equal-to 16-mu-g/ml) = resistant; and cefepime: greater-than-or-equal-to 26 mm (less-than-or-equal-to 2.0-mu-g/ml) = susceptible. Only a susceptible category was defined for cefepime. The results this study indicate that cepfrozil and cefepime may be of value in the treatment of infections due to S. pneumoniae, H. influenzae, and M. catarrhalis.