Antimicrobial activity of Ro 24-6778, a covalent bonding of desmethylfleroxacin and desacetylcefotaxime

A new "dual action" cephalosporin (Ro 24-6778), representing an ester-linked desacetylcefotaxime and desmethylfleroxacin was tested against 287 aerobic bacteria. Ro 24-6778 was found to be very active (minimal inhibitory concentrations [MIC90], less than or equal to 0.5 micrograms/ml) against Enterobacteriaceae, Streptococcus spp., and Aeromonas hydrophila. Moderate Ro 24-6778 activity (MIC90, 1-8 micrograms/ml) was demonstrated against Bacillus spp., Staphylococcus spp. (including oxacillin-resistant strains), Flavobacterium spp., Enterococcus durans, and Acinetobacter anitratus. More Ro 24-6778-resistant strains (MIC90, 16- greater than 32 micrograms/ml) were usually found among the enterococci, Xanthomonas hydrophila, Pseudomonas spp., and Achromobacter xyloxidans isolates. These preliminary Ro 24-6778 MIC test results show a spectrum superior (93.4% of strains susceptible at less than or equal to 8 micrograms/ml) to the comparison drugs (cefotaxime or fleroxacin) and possible clinical utility for therapy of many fluoroquinolone- or cephalosporin-resistant strains.