Cefonicid, a long acting cephalosporin: in vitro activity compared with three cephalosporins and gentamicin.

Minimum inhibitory concentrations of cefonicid, cefazolin, cefuroxime, ceftazidime and gentamicin were determined against 688 bacterial strains (234 Gram-positive and 454 Gram-negative) from 20 different genera. Cefonicid showed a broader spectrum than cefazolin but was not as active as ceftazidime or gentamicin. Cefonicid most closely resembled cefuroxime in terms of microbiological properties. Disc testing accurately predicted sensitivity to cefonicid except for Staphylococcus aureus (which was sensitive by MIC, but appeared resistant in the disc test) and Proteus vulgaris (which was resistant by MIC but appeared sensitive in the disc test). In combination with gentamicin, synergy or addition was observed in 94% of 35 strains tested by the chequerboard technique. In view of its long half-life and wide range of microbiological activity, cefonicid promises to be a useful addition to the range of cephalosporins already available.