Emergence and spread of worldwide Staphylococcus aureus clones among cystic fibrosis patients.

Background: The aim of this study was to assess the relatedness of molecular types of Staphylococcus aureus isolates colonizing cystic fibrosis (CF) patients with their antimicrobial resistance and prevalence of toxin genes.

Methods: A total of 215 isolates from the airways of 107 patients with CF were tested for spa and SCC mec type, antimicrobial resistance and carriage of toxin genes.

Results: t015, t084, t091, t700 and t002 were the largest group (approximately 25%) among all 69 identified spa types. Five new spa types, t14286, t14287, t14288, t14289 and t14290, were identified and registered. Isolates from CF patients were clustered into 11 multi-locus sequence typing clonal complexes, with CC30, CC22, CC97, CC45, CC15 and CC5 being the most frequent ones. Twelve (5.6%) methicillin-resistant S. aureus (MRSA) isolates and 102 (47.7%) multidrug-resistant isolates were identified, along with three SCC mec types (I, III and V). All isolates (both MRSA and methicillin-sensitive S. aureus ) were Panton-Valentine leucocidin-negative, and 56.7% harbored egc genes. This was the first study documenting the presence of ST398-V-t571 livestock-associated MRSA in a European patient with CF.

Conclusion: These findings imply that individuals with CF can also be colonized with animal-related ST398 MRSA, and justify constant monitoring of staphylococcal colonization and identification of epidemic S. aureus clones in this group.