Cefazolin in the treatment of bacterial pneumonia

Cefazolin sodium was tested in vitro against isolates of Diplococcus pneumoniae, Staphylococcus aureus, Klebsiella pneumoniae, and Haemophilus influenzae. Each isolate was tested with at least two inoculum sizes of organisms. Cefazolin also was studied in the treatment of 82 patients with bacterial pneumonia. In concen­trations <1 pg/ml, cefazolin inhibited all isolates of D. pneumoniae and S. aureus, whereas with a larger inoculum of bacterial cells, approximately 10% of K. pneumoniae and H. influenzae grew in concentrations of 25 ytg of antibiotic per ml. Penicillin-sensitive as well as penicillin-resistant isolates of S. aureus were killed by Si 1 pg of cefazolin per ml when the inoculum contained 104 bacteria per ml; however, 25 pg/ml was required to kill 100% of the strains when the inoculum size was increased 100-fold. Clinically, cefazolin treatment appeared to be effective in 74 of 82 patients with pneumonia. Pain was not prominent after im injection, and thrombophlebitis was not observed in those treated by iv injection.