In vitro activity of loracarbef and effects of susceptibility test methods.

Loracarbef is a new oral antimicrobial of the carbacephem class with in vitro activity against the common pathogens associated with skin infections, otitis media, sinusitis, bronchopulmonary infections, and urinary tract infections. A review of the literature shows the following ranges for 90% minimum inhibitory concentration (MIC90) values (microgram/mL) against the organisms that commonly cause these illnesses: Streptococcus pneumoniae, 0.25-2.0; Moraxella (Branhamella) catarrhalis (beta-lactamase positive), 0.5-8.0; M. catarrhalis (beta-lactamase negative), 0.12-0.25; Haemophilus influenzae (beta-lactamase positive), 0.5-16.0; H. influenzae (beta-lactamase negative), 0.25-8.0; Escherichia coli, 2.0-25; Klebsiella pneumoniae, 0.25-8.0; Proteus mirabilis, 1.0-8.0; Streptococcus pyogenes, less than or equal to 0.06-1.0; Staphylococcus aureus (beta-lactamase positive), 8.0; S. aureus (beta-lactamase negative), 1.0-2.0. The in vitro activity of loracarbef against these common outpatient pathogens is similar to that of other oral antimicrobials such as cefaclor, cefuroxime axetil, cefixime, amoxicillin/clavulanate, and trimethoprim/sulfamethoxazole. The results of in vitro susceptibility tests with any antimicrobial, including loracarbef, are somewhat dependent on the specific test method that is employed in the laboratory. This is particularly true with H. influenzae. Furthermore, the results of loracarbef susceptibility tests are of uncertain value in predicting therapeutic outcome.