In vitro antimicrobial activity of loracarbef and its therapeutic efficacy in respiratory tract infections

We measured the in vitro antimicrobial activity of loracarbef (LCBF), a new oral carbacephem developed in Japan, and evaluated its therapeutic efficacy in respiratory infections. The minimum inhibitory concentrations (MICs) of LCBF, cefixime (CFIX), cefteram (CFTM), cefaclor (CCL) and ampicillin (ABPC) against 20 strains each of methicillin-susceptible Staphylococcus aureus (MSSA), methicillin-resistant S. aureus (MRSA), Haemophilus influenzae, Escherichia coli, Klebsiella pneumoniae, Enterobacter cloacae, Serratia marcescens and Pseudomonas aeruginosa were determined by the micro-broth dilution method using the Dynatech MIC 2000 system. As shown by MICs, LCBF was more active than CFIX, CFTM and CCL against MSSA. LCBF was more active than CCL, but less active than ABPC against H. influenzae. Against E. coli and K. pneumoniae, LCBF was more active than CCL and ABPC. Against E. cloacae and 5. marcescens, LCBF was less active than CFIX and CFTM. None of the agents tested showed potent activity against either MRSA or P. aeruginosa. An oral dose of 600~1200 mg of LCBF was given daily to 20 patients for 3 to 15 days (mean: 11.3 days): 2 with acute bronchitis and 9 each with chronic respiratory infections and acute pneumonia. One patient was excluded from clinical evaluation because he had received steroid therapy during the therapy. The clinical effects were excellent in 5, good in 10 and fair in 4 (efficacy rate: 79%). Fifteen strains were identified as causative organisms: 5 strains of Streptococcus pneumoniae, 1 strain each of Streptococcus pyogenes and Moraxella catarrhalis and 8 strains of H. influenzae. Nine of 13 strains against which bacteriological effects could be evaluated were eradicated by an administration of LCBF. No clinical adverse reactions were observed during therapy. Eosinophilia was observed in one patient and an elevation of transaminase in three patients, but these abnormalities in laboratory data disappeared after the completion of therapy. From the above results, we conclude that LCBF is one of the most useful agents for oral use as a first-choice treatment for respiratory tract infections in the outpatient clinic.