Comparison of the in vitro activity of azlocillin and carbenicillin against 856 clinical bacterial isolates.

Eight hundred and fifty-six strains of more than ten species: Staphylococcus aureus, Staphylococcus epidermidis, Streptococcus faecalis, Escherichia coli, Klebsiella spp, Proteus mirabilis, Proteus vulgaris, Enterobacter spp, Pseudomonas spp and Acinetobacter spp, were tested by the disc diffusion method against azlocillin and carbenicillin. Azlocillin was found to be superior to carbenicillin against Pseudomonas spp, and more than 90% of the tested strains had minimal inhibitory concentration (MIC) values well below the serum levels attainable after recommended doses of azlocillin. Against Enterobacteriaceae and Gram-positive cocci, however, azlocillin seemed to have little to offer.