title: Frequent isolation of methicillin resistant Staphylococcus aureus (MRSA) ST398 among healthy pigs in Portugal.
abstract: BACKGROUND
  Although livestock-associated ST398 methicillin-resistant Staphylococcus aureus (MRSA) has been widely reported in different geographic regions, MRSA carriage studies among healthy pigs in Portugal are very limited.
  
  
  RESULTS
  In total, 101 swine nasal samples from two Portuguese farms were screened for MRSA. In addition five swine workers (including one veterinary and one engineer) and four household members were nasally screened. The isolates were characterized by spa typing, SCCmec typing and MLST. All isolates were tested for antimicrobial susceptibility, presence of mecA and mecC genes, and virulence determinants. MRSA prevalence in swine was 99% (100/101), 80% (4/5) in swine workers and 25% (1/4) in household members. All isolates belonged to ST398 distributed over two spa types-t011 (57%) and t108 (42%). SCCmec type V was present in most of the isolates (n = 95; 82%) while 21 isolates amplified the mecA gene only and were classified as nontypeable. The majority of the isolates were resistant to tetracycline (100%), clindamycin (97%), erythromycin (96%), chloramphenicol (84%) and gentamycin (69%). Notably, 12% showed resistance to quinupristin-dalfopristin (MICs 3-8 μg/mL). Beta-hemolysin (81%) and gamma-hemolysin (74%) were the unique virulence determinants detected. None of the isolates harboured PVL or mecC gene.
  
  
  CONCLUSIONS
  This study showed a massive occurrence of ST398-MRSA in two independent swine farms, highlighting its establishment among healthy pigs in Portugal.
authors.affiliation: Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica António Xavier (ITQB), Universidade Nova de Lisboa (UNL), Oeiras, Portugal.
authors.forename: Teresa
authors.initials: T
authors.lastname: Conceição
authors.affiliation: Laboratory of Molecular Genetics, Instituto de Tecnologia Química e Biológica António Xavier (ITQB), Universidade Nova de Lisboa (UNL), Oeiras, Portugal.|Laboratory of Microbiology and Infectious Diseases, The Rockefeller University, New York, NY, United States of America.
authors.forename: Hermínia
authors.initials: H
authors.lastname: de Lencastre
authors.affiliation: Escola Superior de Saúde da Cruz Vermelha Portuguesa (ESSCVP), Lisboa, Portugal.
authors.forename: Marta
authors.identifier: http://orcid.org/0000-0001-5036-2446
authors.initials: M
authors.lastname: Aires-de-Sousa
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D005798:Genes, Bacterial; D055624:Methicillin-Resistant Staphylococcus aureus / Q000187:drug effects / Q000235:genetics / Q000302:isolation & purification*; D008826:Microbial Sensitivity Tests; D011174:Portugal; D013552:Swine / Q000382:microbiology*
chemical_list: D000900:Anti-Bacterial Agents