Antibacterial activity of loracarbef compared with other commonly used oral antibiotics against community-acquired pathogens

Abstract

The in-vitro activity of the new, orally administered carbacephem loracarbef was compared with that of other commonly used oral antibiotics against community-acquired pathogens. A total of 800 recent clinical isolates (350 gram-positive and 450 gram-negative) were examined. The minimal inhibitory concentrations (MICs) were determined by an agar dilution method. The other oral antibiotics tested—cephalexin, cefuroxime, amoxicillin, erythromycin, and amoxicillin/clavulanate—differed from loracarbef in their spectra and their antibacterial potencies. Staphylococcus aureus (200 isolates), Streptococcus pneumoniae (50), and Streptococcus pyogenes (100) were all susceptible to loracarbef at MICs ranging from 0.05 to 8 μg/mL. Only loracarbef had an MIC at which 90% of the isolates were inhibited (MIC 90) of <1 μg/mL against beta-lactamase-negative S aureus. The MIC 90s of most of the other tested drugs were twofold to fourfold higher against beta-lactamase—producing strains that against nonproducing strains of S aureus. the MIC 90 of loracarbef was 2 μg/mL against beta-lactamase—producing and non-producing strains of Haemophilus influenzae. Loracarbef resistance was not noted with strains of H influenzae that lacked beta-lactamase. Amoxicillin/clavulanate and cefuroxime showed good activity against H influenzae (100 isolates) with MIC 90s of 1 to 2 μg/mL. The MIC 90s of loracarbef against Escherichia coli (150), Klebsiella species (100), and Proteus mirabilis (100) were 1 μg/mL while those of the other drugs were 2 to >128 μg/mL. Loracarbef was active against a higher proportion of pathogens that commonly cause community-acquired urinary tract infections than were the other study drugs. Our study indicates that loracarbef offers advantages over the other study drugs for the treatment of community-acquired pathogens that cause upper and lower respiratory tract infections, urinary tract infections, and infections of the skin and soft tissue.