Studies on the antibacterial activity of two new acylureidopenicillins, mezlocillin and azlocillin

Abstract

The antimicrobial activity of 6-[(R)-2[3-methylsulfonyl-2-oxo-imidazolidine-1-carboxamido]-2-phenylacetamido]-penicillanic acid sodium salt (mezlocillin, Baypen) and 6-[(R)-2-(2-oxo-imidazolidine-1-carboxamido)-2-phenylacetamido-a1-penicillanic acid sodium salt (azlocillin, Securopen) was measured against 545 clinical isolates, including gram-negative rods, gram-positive cocci and Bacteroides. Mezlocillin was more effective than azlocillin against the majority of the strains studied, but azlocillin was more effective against Pseudomonas strains. The minimal bactericidal concentration was equal to the minimal inhibitory concentration for the strains tested, but it was twice or four-fold as high for Staphylococcus.