Interactions of antimicrobial drugs and combined phagocytic/serum bactericidal activity of defibrinated human blood against Serratia marcescens. IV. N-formimidoyl thienamycin.

Minimal bactericidal concentrations of thienamycin revealed moderate intraphagolysosomal bactericidal activity against pseudo-(PSR) and genuinely serum-resistant (NSS) assay strains of Serratia marcescens. Combinations of inhibitory and subinhibitory concentrations of thienamycin with 55 vol% of defibrinated human blood resulted in additive effects against all PSR and NSS test strains of S. marcescens and against the NSS Escherichia coli control strain ATCC 25922.