Limited in vitro activity of cefamandole against 100 beta-lactamase- and non-beta-lactamase-producing Haemophilus influenzae strains: comparison of moxalactam, chloramphenicol, and ampicillin.

In the present study, the minimal inhibitory concentrations and minimal bactericidal concentrations of moxalactam, cefamandole lithium, ampicillin, and chloramphenicol were determined, both in broth and on solid medium, against 75 non-beta-lactamase-producing and 25 beta-lactamase-producing strains of Haemophilus influenzae. Most of the 75 strains were inhibited or killed by 2 microgram or less of ampicillin, chloramphenicol, or moxalactam per ml, but cefamandole exhibited poor bactericidal activity against 11 non-beta-lactamase-producing strains, of which 9 were non-type B H. influenzae. Most of the 25 beta-lactamase-producing H. influenzae were resistant to 128 microgram of ampicillin per ml. Both moxalactam and chloramphenicol, which had minimal inhibitory concentrations of less than 0.25 and 2 microgram/ml, respectively, were more active than cefamandole, which had a minimal inhibitory concentration ranging from 2 to greater than or equal to 128 microgram/ml.