Cefotaxime: binding affinity to penicillin-binding proteins and morphological changes of Escherichia coli and Pseudomonas aeruginosa.

The mechanism of action of a new cephalosporin 7-[2-(2-amino-4-thiazolyl)-2-methoximino]-acetamido cephalosporanate (cefotaxime), was studied with respect to its binding affinities to penicillin-binding proteins (PBPs), and morphological changes of bacteria treated by cefotaxime in vitro. Cefotaxime showed especially high affinity (compared with that pf penicillin G) for Escherichia coli PBP-1A, -1Bs, -3 and -4'and low affinities for PBP-2, -4, -5 and -6. Similar results were obtained with Pseudomonas aeruginosa, in which this compound showed high affinities for PBP-3, -1A, -1B and -2. These results are compatible with morphological observations that at concentrations near its minimum inhibitory concentration or more, this antibiotic induced the formation of filamentous cells of Escherichia coli and Pseudomonas aeruginosa. At higher concentrations or after prolonged incubation, it induced lysis of the cells.