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From November 1, 1997 to April 30, 1998, 726 Moraxella catarrhalis isolates and 1529 Haemophilus influenzae isolates were obtained from 34 medical centres throughout the United States. Rates of beta-lactamase production were 94.6% among M. catarrhalis and 31.1% among H. influenzae strains. Susceptibility rates of M. catarrhalis isolates to selected antimicrobial agents were greater than 99% for amoxycillin-clavulanate, cefixime, cefpodoxime, cefuroxime, cefaclor, loracarbef, clarithromycin, azithromycin, chloramphenicol and tetracycline, 97.8% for cefprozil, 50.4% for trimethoprim-sulphamethoxazole and 28.1% for ampicillin. Of the antimicrobials tested against H. influenzae, the only agents with susceptibility rates below 96% were loracarbef (87.6%), cefprozil (83.4%), cefaclor (82.7%), trimethoprim-sulphamethoxazole (67.3%) and ampicillin (64.7%). The clarithromycin susceptibility rate was 67.4% but this agent was not tested in the presence of its 14-OH metabolite.

Original publication




Journal article


International journal of antimicrobial agents

Publication Date





99 - 107


Department of Pathology, University of Iowa College of Medicine, Iowa City 52242, USA.


Humans, Moraxella (Branhamella) catarrhalis, Haemophilus influenzae, Neisseriaceae Infections, Haemophilus Infections, Cross Infection, Anti-Bacterial Agents, Data Collection, Drug Resistance, Microbial, beta-Lactam Resistance, Adolescent, Adult, Aged, Middle Aged, Child, Child, Preschool, Infant, Infant, Newborn, United States, Female, Male