In vitro antimicrobial activities and therapeutic effect on respiratory tract infections of cefotaxime

In vitro antimicrobial activities of cefotaxime (HR 756, CTX), a new cephalosporin derivative, against clinically isolated gram-negative bacilli were examined and its clinical efficacy on respiratory tract infections was evaluated. The peak of distribution of the minimum inhibitory concentrations of cefotaxime against patient strains of Staphylococcus aureus was found at 1.56 μg/ml, and this value was five fold lower than that of sulbenicillin (SBPC) and two fold higher than that of cefazolin (CEZ). Against patient strains of Escherichia coli the peak of distribution of MICs of the drug was at 0.05 μg/ml and it was revealed that the drug had more potent antimicrobial activities than CEZ, dibekacin (DKB) or amikacin (AMK). The peak of distribution of MICs against Klebsiella pneumoniae was at 0.025 μg/ml or less, and the growth of 27 of 29 strains tested was inhibited by the drug at the concentrations of 0.39 μg/ml or less. Against clinical isolates of Pseudomonas aeruginosa the peak of distribution of MICs of the drug was at 25 μg/ml and this value was 3 fold higher and 4 fold lower than those of AMK and SBPC respectively. The pattern of distribution of MICs of the drug against Acinetobacter calcoaceticus was quite similar to that against Pseudomonvs aeruginosa. To make an evaluation of clinical efficacy, one or two grams of the drug was given to 11 patients by intravenous drip infusion. Three patients, i. e. each one of fever of unknown origin, of pulmonary tuberculosis and of lung cancer alone, were omitted and evaluation was made on the remaining 8 patients with respiratory tract infections. In a patient response was excellent. A good response was obtained in 6 patients but in a patient response was poor. In 2 patients among 11 patients treated with the drug, transient elevation of serum GOT and GPT was observed, and in one of them decrease in the number of WBC and platelets was also seen. All these abnormal values returned to normal levels soon after cessation of the administration of the drug.