Activity of imipenem against Pseudomonas and Bacteroides species.

The activity of imipenem against Pseudomonas aeruginosa and Bacteroides fragilis in vitro was studied. MICs of imipenem for P. aeruginosa are approximately 2 micrograms/m. Unlike most other beta-lactam antibiotics, imipenem does not show cross-resistance in the presence of intrinsic resistance. Imipenem is a strong inducer of Id beta-lactamase but is stable to hydrolysis by this enzyme. B. fragilis is more susceptible to imipenem than to other beta-lactam antibiotics. The activity of imipenem against B. fragilis is similar to that of metronidazole. The cephalosporinases of B. fragilis do not inactivate imipenem.