Beta-lactamase stability and antibacterial activity of cefpirome alone and in combination with other antibiotics

The antibacterial activity of cefpirome (HR810), a new cephalosporin, was compared with that of other "third-generation" cephalosporins, as well as cefuroxime, piperacillin and gentamicin. Cefpirome was the most active beta-lactam antibiotic against Gram-negative bacteria. The MIC90 for Enterobacteriaceae was always less than 0.5 ml/l except for Enterobacter species. The MIC90 against Pseudomonas species was 2 mg/l, which was equal to that of ceftazidime and gentamicin. Cefpirome was also more active than the other beta-lactam antibiotics against Staphylococcus aureus. A relatively high frequency of synergy was observed when cefpirome was combined with aminoglycosides against both Gram-positive and Gram-negative bacteria. No antagonism was detected. This antibiotic was very stable to both plasmid- and chromosomally-mediated beta-lactamases. It was more resistant to Enterobacter cloacae P99 enzyme than ceftazidime, cefotaxime and cefotetan. Its stability to the Klebsiella K1 beta-lactamase was more than that of cefotaxime and ceftriaxone but slightly less than that of ceftazidime and latamoxef. MBC90 values for cefpirome were generally less than twice the corresponding MIC values.