A multicenter study of the antimicrobial susceptibility of Haemophilus influenzae, Streptococcus pneumoniae, and Moraxella catarrhalis isolated from patients with community-acquired lower respiratory tract infections in 1999 in Portugal.

A nationwide multicenter study (including 25 laboratories) of the antimicrobial susceptibility of bacterial pathogens commonly associated with community-acquired lower respiratory tract infections (LRTI), with testing undertaken in a central laboratory, was conducted in Portugal in 1999. Antimicrobial resistance in Haemophilus influenzae has not increased in the last decade. Of the 498 isolates tested, 12.4% produced beta-lactamase and >95% were susceptible to all antimicrobials except ampicillin. In contrast, there was a rapid increase of resistance in Streptococcus pneumoniae. Of the 312 isolates tested, 24.7% exhibited decreased susceptibility to penicillin (13.5% showed low-level and 11.2% high-level resistance), 13.8% were resistant to erythromycin, clarithromycin and azithromycin, and 13.6% to cefuroxime and to tetracycline. Of the 38 Moraxella catarrhalis tested, 81.6% produced beta-lactamase. Resistance to penicillin, cefuroxime, erythromycin, clarithromycin, and azithromycin in S. pneumoniae and beta-lactamase production in H. influenzae were significantly higher in pediatric patients than in adults. Overall, amoxycillin/clavulanate was the most active antimicrobial agent in vitro against H. influenzae, S. pneumoniae, and M. catarrhalis isolated from patients with community-acquired LRTI in Portugal.