[In vitro effect of cephacetril and colistin combinations on Klebsiella pneumoniae and Proteus Strains (author's transl)].

In 14 out of 43 Klebsiella pneumoniae strains (33%) the combination cephacetril-colistin showed a synergistic, in 11 strains (25%) an additive effect. In Proteus strains no synergistic action was found. The combination was more likely to be synergistic or additive in strains requiring higher minimal inhibitory concentrations of cephacetril and colistin. Most highly resistant Klebsiella pneumoniae strains were synergistically inhibited by concentrations of both drugs, which can easily be obtained in serum by usual clinical doses.