Enterobacter cloacae outer membrane permeability to ceftizoxime (FK 749) and five other new cephalosporin derivatives.

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Abstract
The ability of ceftizoxime to penetrate the outer membrane was conpared with those of 5 other new cephalosporins: cefotiam, cefuroxime, cefotaxime, cefmetazole and cefoxitin, using a clinical isolate of E. cloaceae as a test strain. Estimation of permeability was performed by a method utilizing the inhibitory activities of the cephalosporins against .beta.-lactamase located in the periplasm. Of the cephalosporins tested, ceftizoxime and cefmetazole gave remarkably high concentrations in the periplasm, several times higher than those of cefotaximine and cefoxitin and 1O or more times higher than those of cefuroxime and cefotiam. The approximate permeability coefficient of ceftizoxime was also several times higher than those of cefotiam and cefmetazole and over 10 times higher than those of cefoxitin, cefuroxime and cefotaxime.