Comparative activity of seven extended-spectrum cephalosporins against Gram-negative bacilli from blood cultures

One hundred sequential Gram-negative rod isolates from patients with hospital-acquired bloodstream infections were tested against seven new cephalosporins. Duplicate broth microdilution tests indicated superior activity for ceftazidime with 97% of strains susceptible to 16 mg/l. Less in-vitro activity was demonstrated cefotaxime (91% susceptible to 16 mg/l, P = 0.07), latamoxef (moxalactam) (90%, P = 0.04), cefoperazone (90%, P = 0.04), ceftriaxone (87%, P = 0.008), cefmenoxime (80%, P = 0.0001), and ceftizoxime (79%, P less than 0.0001). With the exception of cefoperazone, the newer drugs had mean MICs of less than or equal to 0.6 mg/l against Enterobacteriaceae. Ceftazidime and cefoperazone had highest activities against Pseudomonas aeruginosa with MIC90S of 4 and 16 mg/l, respectively. A comparison of recently published data shows important geographic differences in MIC90 data for the new cephalosporins against specific species.