title: The Viriato study: update on antimicrobial resistance of microbial pathogens responsible for community-acquired respiratory tract infections in Portugal.
abstract: The Viriato study is a prospective, multicentre laboratory-based surveillance study of antimicrobial susceptibility in which 30 microbiology laboratories throughout Portugal are asked to isolate, identify and submit to a central laboratory for testing Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis responsible for community-acquired lower respiratory tract infections and Streptococcus pyogenes from tonsillitis. To monitor changes in antimicrobial resistance patterns of these frequent respiratory pathogens. Susceptibility was determined by disk diffusion (Kirby-Bauer) or using Etest strips following the Clinical and Laboratory Standards Institute guidelines. From 1999 to 2007 over 13 900 isolates were analysed. Among S. pneumoniae penicillin non-susceptibility decreased from 25% in 1999 to 18% in 2007 (p = 0.002) but resistance to macrolides showed a steady increase, reaching 20% in the last 6 years. Resistance to amoxicillin and the quinolones remained stable and very low (1-2%) throughout the study period. Antimicrobial resistance among H. influenzae and M. catarrhalis remained stable. The most significant resistance was to ampicillin, of 10-12% and greater than 80%, respectively, as a result of the production of beta-lactamases. Macrolide resistance among S. pyogenes was stable during 1999-2003 (20-23%) but after 2003 there was a steady decline in resistance, which in 2007 reached 10%. The Viriato surveillance study showed that penicillin remains the most active antimicrobial agent against S. pyogenes causing tonsillitis, and amoxicillin-clavulanate and the quinolones are the most active in vitro simultaneously against S. pneumoniae, H. influenzae and M. catarrhalis responsible for community-acquired lower respiratory tract infections in Portugal.
authors.affiliation: Faculty of Medicine, Institute of Microbiology, University of Lisbon, Lisbon, Portugal. melo_cristino@fm.ul.pt
authors.forename: José
authors.initials: J
authors.lastname: Melo-Cristino
authors.forename: Letícia
authors.initials: L
authors.lastname: Santos
authors.forename: Catarina
authors.initials: C
authors.lastname: Silva-Costa
authors.forename: Ana
authors.initials: A
authors.lastname: Friães
authors.forename: Marcos D
authors.initials: MD
authors.lastname: Pinho
authors.forename: Mário
authors.initials: M
authors.lastname: Ramirez
mesh_terms: D000890:Anti-Infective Agents / Q000494:pharmacology*; D001419:Bacteria / Q000187:drug effects; D017714:Community-Acquired Infections / Q000382:microbiology; D024881:Drug Resistance, Bacterial / Q000187:drug effects*; D011174:Portugal; D012141:Respiratory Tract Infections / Q000382:microbiology*
chemical_list: D000890:Anti-Infective Agents