[In vitro activity of imipenem against hospital bacteria].

Imipenem proved highly active against Enterobacteriaceae: the different bacterial groups exhibited similar mode MICs (0.12 to 0.25 micrograms/ml), except for Serratia (0.25-0.5 micrograms/ml), Proteus mirabilis (0.5 micrograms/ml), indole-positive Proteus (2 micrograms/ml) and Providencia (1 mu/ml). The MICs of cefotaxime-resistant strains (cephalosporinase hyperproducing or very broad spectrum betalactamase producing) were within the susceptibility range. Imipenem also exhibited satisfactory activity against Pseudomonas aeruginosa (mode MIC 1-2 micrograms/ml), although resistant strains by decrease of permeability were observed, and against Acinetobacter (mode MIC 0.25-0.5 micrograms/ml). The MICs ranged from 0.03 to 4 micrograms/ml (mode MIC 0.5) for Haemophilus and from 0.25 to 1 micrograms/ml for Neisseria gonorrhoeae, regardless of the betalactamase producing status. The MICs for N. meningitidis were less than 0.06 micrograms/ml. Methicillin-susceptible staphylococci had low MICs ranging from 0.008 to 0.5 micrograms/ml (mode MIC 0.016). The MICs for methicillin-resistant strains varied widely from 0.016 to 64 micrograms/ml and were higher after incubation at 30 degrees C. Streptococci and pneumococci were highly susceptible (usually 0.008 to 0.03 micrograms/ml). The MICs for enterococci varied from 0.12 to 32 micrograms/ml (mode MIC 1-2). With the exception of Clostridium difficile, anaerobic bacteria were inhibited by concentrations lower than 1 (mode MIC 0.06 for C. Perfringens and 0.03 for Bacteroides fragilis).