Comparative activities of moxalactam (LY 127935) a new semisynthetic 1-oxa-beta lactam antibiotic with 7 other antibiotics against type b Haemophilus influenzae.

A total of 59 clinical isolated strains of Haemophilus influenzae type b, including 22 beta-lactamase-positive strains, were tested against moxalactam (LY 127935), a new 1-oxa-beta-lactam antibiotic and compared with other antibiotics: cefamandole, cefoxitin, ceforanide, ampicillin, ticarcillin, chloramphenical and trimethoprim/sulfamethoxazole (TMP/SMZ) by using an agar dilution susceptibility test and bacterial killing rate study. With beta-lactamase negative H. influenzae all 37 strains were inhibited by ampicillin at concentration less than or equal to 0.2 microgram/ml, in contrast all beta-lactamase positive strains were exhibited by a range from 3.2 micrograms/ml to 25 micrograms/ml. Ticarcillin inhibited 100% of non-beta lactamase strains at 0.4 micrograms/ml in contrast to those beta-lactamase producing strains the range was from 0.8 microgram/ml to 12.5 micrograms/ml. All strains were inhibited by 0.8 microgram/ml of chloramphenicol and by 0.078/1.56 microgram of TMP/SMZ per ml. Among the beta-lactam antibiotics, moxalactam (LY 127935) show 100% inhibited all strains by 0.1 microgram/ml in comparison with cefamandole, cefoxitin and ceforanide most strains inhibited by 0.4 microgram/ml, 2 micrograms/ml and 4 micrograms/ml, respectively. From the killing curve study, during the first 6 hours, each antibiotic had the effect of inhibition growing of both strains of H. influenzae. But after 24 hours incubation, only moxalactam (LY 127935) showed bactericidal effect. These data indicate that moxaladam, a new 1-oxa-beta-lactam antibiotic, had superior inhibitory activity and killing effect against both beta-lactamase producing and non-beta-lactamase producing strains of H. influenzae type b.