Molecular characterisation of methicillin-resistantStaphylococcus aureusfrom chronically colonised cystic fibrosis paediatric patients in Brazil

Abstract

Persistent methicillin-resistantStaphylococcus aureus(MRSA) infection in cystic fibrosis (CF) patients has been associated with a more rapid decline in lung function, increased hospitalisation and mortality. The aim of this study was to evaluate the clonal relationships among 116 MRSA isolates from 12 chronically colonised CF pediatric patients over a 6-year period in a Rio de Janeiro CF specialist centre. Isolates were characterised by antimicrobial resistance, SCCmectype, presence of Panton-Valentine Leukocidin (PVL) genes and grouped according to DNA macrorestriction profile by pulsed-field gel electrophoresis (PFGE) andspagene type. High resistance rates were detected for erythromycin (78%) and ciprofloxacin (50%) and SCCmecIV was the most common type (72.4%). Only 8.6% of isolates were PVL positive. High genetic diversity was evident by PFGE (39 pulsotypes) and of nine that were identifiedspatypes, t002 (53.1%) and t539 (14.8%) were the most prevalent. We conclude that the observed homogeneity ofspatypes within patients over the study period demonstrates the persistence of such strain lineages throughout the course of chronic lung infection.