Evaluation of antibiotic efficacy using electron microscopy: morphological effects of guanylureido cephalosporin, chlorobenzoylureido cephalosporin, BL-P1654, and carbenicillin on Pseudomonas aeruginosa.

The response of Pseudomonas aeruginosa to carbenicillin, BL-P1654, and two cephalosporins (112384 and 112883) was evaluated by minimal inhibitory concentration determinations, [(14)C]leucine uptake studies, morphological studies of colonial growth, and mouse intraperitoneal inoculations. Spheroplast formation and bacterial lysis were not the early response; instead, cell division was inhibited and long filaments were formed. Spheroplast formation and bacterial lysis were not observed in the first 7 h of incubation in minimal inhibitory concentrations of antibiotic.