In vitro action of carbenicillin against bacteria isolated from clinical material.

More than 500 bacteria isolated from patient material were tested against carbenicillin (disodium alpha-carboxybenzylpenicillin) by diffusion and dilution modalities. The same bacteria, which included Pseudomonas aeruginosa, Escherichia coli, Klebsiella-Aerobacter-Enterobacter group, various species of Proteus, Staphylococcus aureus and epiddermidis, enterococci, pneumococci, Streptococcus pyogenes, etc., were examined for susceptibility to other antibiotics commonly used with special emphasis on ampicillin and cephalothin. The responses of pyocine-typed P. aeruginosa were the most remarkable. The majority of these bacteria displayed susceptibility to carbenicillin by both the dilution and the diffusion techniques. The concentrations of this antibiotic used in the laboratory were of the same order of magnitude as that of the other drugs. The laboratory behavior of the other bacteria, toward this new semisynthetic penicillin derivative approximated their response to ampicillin and cephalothin.