Thienamycin: new beta-lactam antibiotic with potent broad-spectrum activity.

Thienamycin, a new beta-lactam antibiotic, exhibited potent, broad-spectrum activity in vitro against gram-negative bacilli and gram-positive cocci, including many isolates resistant to currently available antibiotics. All isolates were inhibited at concentrations less than or equal to 25 mug/ml, with the exception of 12% of isolates of Enterobacter spp. and 3% of isolates of Serratia marcescens. Its activity decreased with an increase in inoculum concentration of from 10(5) to 10(7) cells per ml.