title: Whole-genome comparison of meticillin-resistant Staphylococcus aureus CC22 SCCmecIV from people and their in-contact pets.
abstract: BACKGROUND
  Meticillin-resistant Staphylococcus aureus (MRSA) infections remain important medical and veterinary challenges. The MRSA isolated from dogs and cats typically belong to dominant hospital-associated clones, in the UK mostly EMRSA-15 (CC22 SCCmecIV), suggesting original human-to-animal transmission. Nevertheless, little is known about host-specific genetic variation within the same S. aureus lineage.
  
  
  OBJECTIVE
  To identify host-specific variation amongst MRSA CC22 SCCmecIV by comparing isolates from pets with those from in-contact humans using whole-genome microarray.
  
  
  METHODS
  Six pairs of MRSA CC22 SCCmecIV from human carriers (owners and veterinary staff) and their respective infected in-contact pets were compared using a 62-strain whole-genome S. aureus microarray (SAM-62). The presence of putative host-specific genes was subsequently determined in a larger number of human (n = 47) and pet isolates (n = 93) by PCR screening.
  
  
  RESULTS
  Variation in mobile genetic elements (MGEs) occurred frequently and appeared largely independent of host and in-contact pair. A plasmid (SAP078A) encoding heavy-metal resistance genes (arsR, arsA, cadA, cadC, mco and copB) was found in three of six human and none of six animal isolates. However, only two of four resistance genes were associated with human hosts (P = 0.015 for arsA and cadA).
  
  
  CONCLUSIONS
  The variation found amongst MGEs highlights that genetic adaptation in MRSA continues. However, host-specific MGEs were not detected, which supports the hypothesis that pets may not be natural hosts of MRSA CC22 and emphasizes that rigorous hygiene measures are critical to prevent contamination and infection of dogs and cats. The host specificity of individual heavy-metal resistance genes warrants further investigation into different selection pressures in humans and animals.
authors.affiliation: Department of Veterinary Clinical Sciences, Royal Veterinary College, University of London, Hawkshead Lane, North Mymms, Hatfield, Hertfordshire, AL9 7TA, UK.
authors.forename: Anette
authors.initials: A
authors.lastname: Loeffler
authors.forename: Alex
authors.initials: A
authors.lastname: McCarthy
authors.forename: David H
authors.initials: DH
authors.lastname: Lloyd
authors.forename: Eva
authors.initials: E
authors.lastname: Musilová
authors.forename: Dirk U
authors.initials: DU
authors.lastname: Pfeiffer
authors.forename: Jodi A
authors.initials: JA
authors.lastname: Lindsay
mesh_terms: D000818:Animals; D002371:Cat Diseases / Q000382:microbiology; D002415:Cats; D004283:Dog Diseases / Q000382:microbiology; D004285:Dogs; D005260:Female; D014644:Genetic Variation; D016680:Genome, Bacterial; D006801:Humans; D020071:Interspersed Repetitive Sequences; D008297:Male; D055624:Methicillin-Resistant Staphylococcus aureus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification*; D020411:Oligonucleotide Array Sequence Analysis; D057805:Pets; D013203:Staphylococcal Infections / Q000382:microbiology / Q000662:veterinary*; D013207:Staphylococcal Skin Infections / Q000382:microbiology / Q000662:veterinary*