Carbenicillin, a 9-alpha carboxybenzyl penicillin, is bactericidal only for Escherichia coli strains which are resistant to less than 125 μg./ml. of ampicillin. All E. coli and Salmonella typhimurium strains in which penicillinase is a surface enzyme are resistant to carbenicillin. E. coli and S. typhimurium strains in which production of beta-lactamase is episomally mediated are resistant to both ampicillin and carbenicillin. A non-hydrolyzable penicillin (methicillin or dicloxacillin) does not allow carbenicillin to exert its antibacterial effect against resistant strains of E. coli, Pseudomonas, Klebsiella or Enterobacter. Carbenicillin shows no synergy with penicillinase-resistant penicillins.
AcredP.,
BrownD. M.,
KnudsenE. T.,
RobinsonG. N.,
SutherlandR.1967; New sem synthetic penicillin active against Pseudomonas pyocyanea
. Nature, Lond 215:25
BrumfittW.,
PercivalA.,
LeighD. A.1967; Clinical and laboratory studies with carbenicillin, a new penicillin active against Pseudomonas pyocyanea
. Lancet 1:1289
SutherlandR.,
BatchelorF. R.1964; Synergistic activity of penicillins against penicillinase from gram-positive and gram-negative bacteria by substrate analogues. Nature, Lond 201:868