Antimicrobial susceptibility of Streptococcus pyogenes, Haemophilus influenzae, Streptococcus pneumoniae and Moraxella catarrhalis from community acquired respiratory infections in 2000.

Abstract

The Viriato Study is a nationwide, multicenter prospective study of the antimicrobial susceptibility of bacterial pathogens commonly associated with community-acquired respiratory tract infections in Portugal. In 2000, 28 laboratories participated in the study with a total of 1071 strains, with testing undertaken in a central laboratory. Of the 213 Streptococcus pyogenes strains isolated from patients with acute tonsillitis, all were susceptible to penicillin, amoxicillin/clavulanate and cefuroxime, but 21.1% were resistant to erythromycin, clarithromycin, azithromycin and 16.4% to tetracycline. From patients with lower respiratory tract infection, 403 strains of Haemophilus influenzae, 366 of Streptococcus pneumoniae and 89 of Moraxella catarrhalis were studied. 13.1% of H. influenzae and 94.4% of M. catarrhalis produced beta-lactamase. Among S. pneumoniae isolates, 25.1% were resistant to penicillin (8.8% showing high-level resistance), 14.5% to tetracycline, 12.8% to erythromycin, clarithromycin and azithromycin, and 10.1% to cefuroxime. Overall, penicillin was the most active antimicrobial against S. pyogenes and amoxycillin/clavulanate the most active in vitro simultaneously against H. influenzae, S. pneumoniae and M. catarrhalis isolated from patients with community-acquired LRTI in Portugal.