Activity of oral beta-lactam antimicrobial agents versus respiratory tract isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis in the era of antibiotic resistance.

Abstract

The management of outpatient respiratory tract infections with oral beta-lactam antimicrobial agents has been complicated by the emergence of beta-lactamase-producing strains of Haemophilus influenzae and Moraxella catarrhalis and isolates of Streptococcus pneumoniae that express varying levels of beta-lactam resistance because of altered penicillin-binding proteins. There is no question that all 3 of these important respiratory tract pathogens have changed conspicuously in the context of decreased activity of beta-lactam antimicrobial agents. The question arises, what does this change mean from a clinical perspective? In this review, the in vitro activity of various oral beta-lactam antimicrobial agents versus contemporary isolates of H influenzae, M catarrhalis, and S pneumoniae will be compared. The approach that is used in defining organisms as being susceptible or resistant to beta-lactam antimicrobial agents will be elucidated. Finally, an effort will be made to assess the ramifications of beta-lactam resistance for therapeutic efficacy in patients with respiratory tract infections caused by these 3 bacteria. We conclude that, notwithstanding diminished beta-lactam activity for many clinical isolates of H influenzae, M catarrhalis, and S pneumoniae, certain agents remain effective in treating outpatient respiratory tract infections.