[Comparison of antibacterial activities of cephalosporins].

2770 strains of Enterobacteriacea and of Acinetobacter were examined for susceptibility to cefoperazone, cefotaxime, ceftazidim, ceftriaxone, lamoxactam and cefotiam with the disk diffusion test. The percentage of susceptible strains was between 92% and 99%. Strains resistant to the new cephalosporins were more frequently observed in Enterobacter species, Serratia marcescens and Proteus vulgaris. A comparison with the activity of cefamandole, cefoxitin and cefuroxime showed the improvement which has been obtained by the development of the newer cephalosporins. Third generation cephalosporins showed variable activity against Pseudomonas aeruginosa. Modal MICs of cefoperazone, cefsulodin and ceftazidim were between 2-4 mg/l, whereas mode MICs of cefotaxime, ceftriaxone and lamoxactam were 16 mg/l. Of 591 examined Pseudomonas strains, 75, 90 and 96% respectively were susceptible to the first-named three derivatives in agar diffusion tests. Two to 60% of these cultures were susceptible to the second group of cephalosporins. These data show the unreliability of the disk test in testing Pseudomonas with these cephalosporins. Cefalothin, cefamandole and cefotiam were most active against staphylococci (mean MICs 0.25-0.5 mg/l). Lamoxactam, ceftazidim and cefsulodin showed only moderate activity (mean MICs 6.3-10.2 mg/l). All cephalosporins were inactive against enterococci, but showed good activity against streptococci and pneumococci.