Comparison of in vitro susceptibilities among gram-negative rods.

The activity of mezlocillin, azlocillin and piperacillin was compared using 100 clinical isolates of gram-negative rods. Overall piperacillin had the highest activity with 72 per cent sensitive strains; mezlocillin, 66 per cent, and azlocillin, 57 per cent. In the group of Pseudomonas aeruginosa, however, mezlocillin showed distinctly lower activity than both piperacillin and azlocillin.