[Curative action of mezlocillin on experimental infections in mice (author's transl)].

The curative action of mezlocillin on 10 severe experimental infections in mice was determined and expressed as effective dose 50 (ED50). The ED50 against infections produced by 5 strains of Gram-positive bacteria was distinctly lower than the ED50 against infections produced by 5 strains of Gram-negative bacteria. Infections due to Proteus mirabilis and Klebsiella pneumoniae were the least susceptible to mezlocillin. The determination of MICs and MBCs of mezlocillin against the strains used in the experiments showed a linear relationship between MBC and ED50 for Listeria spp., E. coli spp., S. typhimurium and Pr. mirabilis. For strains of 3 species (S. pyogenes, S. pneumoniae and E. insidiosa) with very low MBCs, the ED50 was related to virulence. The diversity of the results shows that various types of experimental infections should be used when testing an antibiotic.