The Viriato Study: Update on Antimicrobial Resistance of Microbial Pathogens Responsible for Community-Acquired Respiratory Tract Infections in Portugal

• Published in: Paediatric drugs 2010-06, Vol.12 (Suppl 1), p.11-17
• Main Authors: Melo-Cristino, José, Santos, Letícia, Silva-Costa, Catarina, Friães, Ana, Pinho, Marcos D., Ramirez, Mário
• Format: Article
• Language: English
• Subjects: Internal Medicine; Medicine; Medicine & Public Health; Original Research Article; Pediatrics; Pharmacotherapy
• ISSN: 1174-5878; 1179-2019
• DOI: 10.2165/11538730-S0-000000000-00003

Background: 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. Objective: To monitor changes in antimicrobial resistance patterns of these frequent respiratory pathogens. Methods: Susceptibility was determined by disk diffusion (Kirby-Bauer) or using Etest strips following the Clinical and Laboratory Standards Institute guidelines. Results: 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 β-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%. Conclusion: 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.