Uptake of (methyl-14C)-sisomicin and (methyl-14C)-gentamicin into bacterial cells.

Eight sensitive strains (two Staphylococcus aureus, two Escherichia coli, two Pseudomonas aeruginosa and two Klebsiella pneumoniae) and four resistant Pseudomonas aeruginosa strains were used to study uptake of sisomicin and gentamicin by the bacterial cells. In eleven out of the twelve organisms studied employing (methyl-14C)-sisomicin and (methyl-14C)-gentamicin, uptake of the former was found higher that that of the latter. In one organism, the uptake of the two antibiotics was similar. This higher uptake of sisomicin may help explain the superior potency of the antibiotic in relation to gentamicin.