Antimicrobial activity of E-1040, a novel thiadiazolyl cephalosporin compared with other parenteral cephems.

E-1040, a new parenteral fourth-generation cephalosporin, was tested against greater than 600 bacteremic pathogens and compared with cefotaxime, ceftazidime, and cefpirome. E-1040 activity against Staphylococcus aureus was comparable (MIC90, 8 micrograms/ml) to ceftazidime, but inferior to cefotaxime (MIC90, 2 micrograms/ml) and cefpirome (MIC90, 0.5 microgram/ml). beta-Hemolytic streptococci and most Gram-positive anaerobes were also susceptible to E-1040. Some strains of coagulase-negative staphylococci, all oxacillin-resistant Staphylococcus spp., enterococci, and Bacteroides fragilis group strains were resistant to E-1040 (MIC90, greater than 64 micrograms/ml). Comparative tests for E-1040 and the three other cephalosporins against pseudomonads and nonenteric Gram-negative bacilli showed E-1040 to be generally most active. The E-1040 MIC90 for Pseudomonas aeruginosa was 1 microgram/ml and for ceftazidime it was 4 micrograms/ml. Haemophilus influenzae, Moraxella catarrhalis, and Neisseria spp. has E-1040 MIC90s ranging from 0.12 to 2 micrograms/ml. Neisseria gonorrhoeae, strains resistant to penicillin, did not have markedly elevated E-1040 MICs compared with penicillin-susceptible strains. Enterobacteriaceae species had all MICs of less than or equal to 8 micrograms/ml for E-1040 and cefpirome, indicating activity against strains producing stably derepressed beta-lactamases. E-1040 appeared to be beta-lactamase stable, little influenced by testing systems or media, and was bactericidal. E-1040 seems to have promise as a parenteral beta-lactam for use on strains resistant to "third-generation" cephalosporins and other families of drugs such as aminoglycosides and fluoroquinolones.