Activity of N-formimidoyl thienamycin and cephalosporins against isolates from nosocomially acquired bacteremia.

The in vitro activity of N-formimidoyl thienamycin was compared with that of seven beta-lactam agents against bacteremic clinical isolates, including gentamicin-resistant, gram-negative bacilli, Staphylococcus aureus, Staphylococcus epidermidis, streptococci, and enterococci. N-formimidoyl thienamycin was the most active antibiotic against all of the gram-positive cocci studied, with the exception of Staphylococcus epidermidis, and the only agent active against the enterococci. N-formimidoyl thienamycin was less active than some of the other agents against Enterobacteriaceae, except for the strains of Serratia and Citrobacter studied. For Pseudomonas aeruginosa, N-formimidoyl thienamycin was the most active agent (4 micrograms/ml was the lowest concentration that inhibited 90% of the strains tested).