In vitro activity of N-formimidoyl-thienamycin in comparison to that of moxalactam and cefotaxime against gentamicin-resistant gram-negative bacteria.

The inhibitory and bactericidal activity of N-formimidoyl-thienamycin in vitro against 131 clinical isolates selected for their gentamicin resistance was compared with that of cefotaxime and moxalactam. All strains were inhibited by N-formimidoyl-thienamycin concentrations within a range of 0.12-4 mg/l. N-formimidoyl-thienamycin was less active than cefotaxime and moxalactam against Escherichia coli and Klebsiella spp., and more active than all other antibiotics tested against Serratia spp., Enterobacter cloacae, Pseudomonas aeruginosa and Acinetobacter spp. In contrast to the other antibiotics N-formimidoyl-thienamycin showed a narrow margin of difference between minimal inhibitory and minimal bactericidal concentrations. N-formimidoyl-thienamycin is a promising antibiotic for the treatment of hospital infections with multi-resistant organisms.