ORIGINAL ARTICLE Detection of methicillin-resistant Staphylococcus aureus in Iberian pigs M.C. Porrero 1 , T.M. Wassenaar 2 , S. Go ´ mez-Barrero 1 , M. Garcı´a 1 , C. Ba ´ rcena 1,3 , J. A ´ lvarez 1,4 , J.L. Sa ´ ez- Llorente 5 , J.F. Ferna ´ ndez-Garayza ´ bal 1,6 , M.A. Moreno 1,6 and L. Domı´nguez 1 1 VISAVET Health Surveillance Centre, Universidad Complutense, Madrid, Spain 2 Molecular Microbiology and Genomics Consultants, Zotzenheim, Germany 3 Unidad de Microbiologı´a, Virologı´a e Inmunologı´a, Departamento de Patologı´a Animal (Sanidad Animal), Facultad de Veterinaria, Universidad de Zaragoza, Zaragoza, Spain 4 Instituto de Investigacio ´ n en Recursos Cinege ´ ticos IREC (CSIC-UCLM-JCCM), Ronda de Toledo, Ciudad Real, Spain 5 Subdireccio ´ n General de Sanidad de la Produccio ´ n Primaria, Direccio ´n General de Recursos Agrı´colas y Ganaderos, Ministerio de Medio Ambiente y Medio Rural y Marino, Madrid, Spain 6 Departamento de Sanidad Animal. Facultad de Veterinaria, Universidad Complutense de Madrid, Madrid, Spain Introduction Methicillin-resistant Staphylococcus aureus (MRSA) pre- sents a major health problem in humans as it is a common cause of nosocomial infections, displaying a complex epi- demiology (Tacconelli 2009). The problem is partly caused by hospital-acquired infections, but MRSA infections acquired in the community can also pose serious health risks (Vozdecky 2009). MRSA can be isolated from a variety of animal species, including pets and food-producing animals, which may become colonized as a result of zooan- troponotic transfer (Epstein and Price 2009). Such animals can potentially serve as a reservoir for human infection (Cuny et al. 2010). MRSA can cause veterinary clinical cases, and in addition, just like humans, asymptomatic ani- mal carriers can be the source of recurrent infections in ani- mal hospitals or in humans (Leonard et al. 2006; Juhasz- Kaszanyitzky et al. 2007; Graveland et al. 2010). Keywords Iberian pig, MLST, MRSA, spa type, ST398. Correspondence Lucas Domı ´nguez, VISAVET Health Surveillance Centre, Universidad Complutense, Avenida Puerta de Hierro, s ⁄ n 28040 Madrid, Spain. E-mail: lucasdo@visavet.ucm.es 2011 ⁄ 1989: received 22 November 2011, revised 27 December 2011 and accepted 28 December 2011 doi:10.1111/j.1472-765X.2012.03207.x Abstract Aims: Iberian pigs are bred in Spain for the production of high-value dry- cured products, whose export volumes are increasing. Animals are typically reared outdoors, although indoor farming is becoming popular. We compared carriage of methicillin-resistant Staphylococcus aureus (MRSA) in Iberian pigs, raised indoors and outdoors, with intensively farmed Standard White pigs. Methods and Results: From June 2007 to February 2008, 106 skin swabs were taken from Iberian pigs and 157 samples from SWP at slaughterhouses in Spain. We found that Iberian pigs carried MRSA, although with a significantly lower prevalence (30 ⁄ 106; 28%) than SWP (130 ⁄ 157; 83%). A higher prevalence of indoor Iberian pigs compared with animals reared under outdoor conditions was not significant; however, all but one positive indoor Iberian pig samples were detected from one slaughterhouse. Overall, 16 different spa types were identified, with t011 predominating in all three animal populations. A subset of isolates was characterized by MLST. Most of these belonged to ST398. MRSA isolates from Iberian pigs presented a higher susceptibility to antibiotics than those isolated from SWP. Conclusions: Despite limited contact with humans, pigs raised outdoors are colonized by an MRSA population that genetically overlaps with that of intensively farmed pigs, although antimicrobial resistance is lower. Significance and Impact of the Study: To our knowledge, this is the first detection of MRSA in food animals raised in free-range conditions. Letters in Applied Microbiology ISSN 0266-8254 280 Letters in Applied Microbiology 54, 280–285 ª 2012 The Society for Applied Microbiology ª 2012 The Authors