Antimicrobial susceptibilities of Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis isolated in two successive respiratory seasons in the US.

Antimicrobial susceptibilities of clinical isolates of Streptococcus pneumoniae, Haemophilus influenzae, and Moraxella catarrhalis were determined in two consecutive respiratory seasons in the US and suggested that national susceptibilities to commonly tested antimicrobials changed only slightly from the 1999-2000 to the 2000-2001 respiratory season. However, a significant regional variation in S. pneumoniae susceptibilities was observed, as was a decrease in beta-lactamase rates among H. influenzae from the 1999-2000 to 2000-2001 respiratory seasons.