title: What Is the Origin of Livestock-Associated Methicillin-Resistant Staphylococcus aureus Clonal Complex 398 Isolates from Humans without Livestock Contact? An Epidemiological and Genetic Analysis.
abstract: Fifteen percent of all methicillin-resistant Staphylococcus aureus (MRSA) clonal complex 398 (CC398) human carriers detected in The Netherlands had not been in direct contact with pigs or veal calves. To ensure low MRSA prevalence, it is important to investigate the likely origin of this MRSA of unknown origin (MUO). Recently, it was shown that CC398 strains originating from humans and animals differ in the presence of specific mobile genetic elements (MGEs). We hypothesized that determining these specific MGEs in MUO isolates and comparing them with a set of CC398 isolates of various known origin might provide clues to their origin. MUO CC398 isolates were compared to MRSA CC398 isolates obtained from humans with known risk factors, a MRSA CC398 outbreak isolate, livestock associated (LA) MRSA CC398 isolates from pigs, horses, chickens, and veal calves, and five methicillin-susceptible Staphylococcus aureus (MSSA) CC398 isolates of known human origin. All strains were spa typed, and the presence or absence of, scn, chp, φ3 int, φ6 int, φ7 int, rep7, rep27, and cadDX was determined by PCRs. The MRSA CC398 in humans, MUO, or MRSA of known origin (MKO) resembled MRSA CC398 as found in pigs and not MSSA CC398 as found in humans. The distinct human MSSA CC398 spa type, t571, was not present among our MRSA CC398 strains; MRSA CC398 was tetracycline resistant and carried no φ3 bacteriophage with scn and chp. We showed by simple PCR means that human MUO CC398 carriers carried MRSA from livestock origin, suggestive of indirect transmission. Although the exact transmission route remains unknown, direct human-to-human transmission remains a possibility as well.
authors: Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands RIVM, National Institute for Public Health and the Environment, Bilthoven, The Netherlands w.lekkerkerk@erasmusmc.nl.
authors: W S N
authors: WS
authors: Lekkerkerk
authors: Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
authors: W J B
authors: WJ
authors: van Wamel
authors: Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
authors: S V
authors: SV
authors: Snijders
authors: Department of Medical Microbiology, University Medical Centre Utrecht, Utrecht, The Netherlands.
authors: R J
authors: RJ
authors: Willems
authors: RIVM, National Institute for Public Health and the Environment, Bilthoven, The Netherlands.
authors: E
authors: E
authors: van Duijkeren
authors: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands.
authors: E M
authors: EM
authors: Broens
authors: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands Central Veterinary Institute (CVI) of Wageningen UR, Lelystad, The Netherlands.
authors: J A
authors: JA
authors: Wagenaar
authors: Centre for Infection, Division of Clinical Sciences, St George's University of London, London, United Kingdom.
authors: J A
authors: JA
authors: Lindsay
authors: Department of Medical Microbiology and Infectious Diseases, Erasmus MC, University Medical Centre, Rotterdam, The Netherlands.
authors: M C
authors: MC
authors: Vos
mesh_terms: D000818:Animals; D002417:Cattle; D002645:Chickens; D015331:Cohort Studies; D006736:Horses; D006801:Humans; D015994:Incidence; D055624:Methicillin-Resistant Staphylococcus aureus / Q000235:genetics*; D013203:Staphylococcal Infections / Q000453:epidemiology / Q000382:microbiology / Q000635:transmission* / Q000662:veterinary*; D013552:Swine