Evaluation of two commercially available chromogenic media for confirmation of methicillin-resistant Staphylococcus aureus from human, animal, and food samples Jaime Ariza-Miguel a , Elena-Alexandra Oniciuc b , Iván Sanz c , Isabel Fernández-Natal d,e , Marta Hernández a , David Rodríguez-Lázaro a,f, ⁎ a Instituto Tecnológico Agrario de Castilla y León, Valladolid, Spain b Faculty of Food Science and Engineering, Dunarea de Jos University of Galati, Romania c Valladolid National Influenza Center, Valladolid, Spain d Complejo Asistencial Universitario de León, León, Spain e Institute of Biomedicine (IBIOMED), University of León, Leon, Spain f Microbiology Section, Department of Biotechnology and Food science, Faculty of Science, University of Burgos, Burgos, Spain abstract article info Article history: Received 30 March 2015 Received in revised form 26 April 2015 Accepted 10 May 2015 Available online xxxx Keywords: Methicillin-resistant Staphylococcus aureus Chromogenic media Screening We compared the diagnostic performance of two chromogenic media, Brilliance MRSA 2 agar (Thermo Fisher Scientific) and ChromID MRSA agar (bioMérieux), for MRSA confirmation of 239 Staphylococcus aureus isolates from clinical, animal and food samples. Statistically significant differences were not observed between MRSA confirmation by mecA/mecC PCR, and by culture in both chromogenic media. However, a statistically significant difference was observed between the results obtained by both chromogenic media (p = 0.003). Segregated anal- ysis of the results depending on the origin of the isolates (clinical, animal, and food) revealed a significant lower performance in the MRSA confirmation of food-derived isolates by using Brilliance MRSA 2 agar in comparison to PCR confirmation (p = 0.003) or ChromID MRSA agar (p b 0.001). Both chromogenic media provided a good di- agnostic performance for detection of MRSA isolates of human and animal origin. In conclusion, the use of chro- mogenic agar plates for MRSA confirmation of S. aureus isolates can provide a good diagnostic performance (sensitivity N 92% and specificity N 89%) regardless of the type of chromogenic media used or the origin of the S. aureus isolates. However, our results revealed a lower diagnostic performance for MRSA confirmation of S. aureus isolates from food samples by using Brilliance MRSA 2 agar. © 2015 Elsevier B.V. All rights reserved. 1. Introduction Dissemination of methicillin-resistant Staphylococcus aureus (MRSA) from the health care system to community and animal settings in the last two decades has elicited a great concern (Graveland et al., 2011; Okuma et al., 2002). Furthermore, the emergence of MRSA in food-producing animals and derived food products has raised the ques- tion on the potential role of food as a route for transmission of successful livestock and community associated MRSA lineages (Oniciuc et al., in this issue; Rodríguez-Lázaro et al., in this issue). Therefore, monitoring the presence and genetic features of MRSA in all environments and po- tential reservoirs is required to better understand the dissemination, ge- netic evolution and evolutionary success of epidemic MRSA lineages. Several commercially available chromogenic media have been developed to facilitate the screening of MRSA, and some studies have assessed their diagnostic performance (McElhinney et al., 2013; Veenemans et al., 2013; Verkade et al., 2011). However, they have been mainly focused in human clinical samples, and there is a knowl- edge gap regarding MRSA from animal and food samples. Therefore, in this study we evaluated the performance of Brilliance MRSA 2 Agar (Thermo Fisher Scientific, Waltham, MA, USA) and ChromID MRSA Agar (bioMérieux, France) as rapid MRSA confirmation screening assays for S. aureus isolates from a wide range of origins: clinical, animal and food samples. We assessed, by using the McNemar's test for paired sam- ples, if there are statistically significant differences among a reference method, the molecular detection of resistance genes mecA and mecC, and MRSA confirmation by using both chromogenic media. Further- more, we have compared the diagnostic performance between the chromogenic media. 2. Material and methods 2.1. Bacterial isolates A collection of 239 S. aureus isolates, comprising 154 methicillin- sensitive S. aureus isolates (MSSA), 83 MRSA isolates harbouring mecA, and two MRSA isolates harbouring mecC, were selected to perform the International Journal of Food Microbiology xxx (2015) xxx–xxx ⁎ Corresponding author at: Instituto Tecnológico Agrario de Castilla y León (ITACyL), Consejería de Agricultura y Ganadería, Junta de Castilla y León, Carretera de Burgos km. 119, Valladolid, Spain. E-mail address: rodlazda@gmail.com (D. Rodríguez-Lázaro). FOOD-06918; No of Pages 3 http://dx.doi.org/10.1016/j.ijfoodmicro.2015.05.004 0168-1605/© 2015 Elsevier B.V. All rights reserved. Contents lists available at ScienceDirect International Journal of Food Microbiology journal homepage: www.elsevier.com/locate/ijfoodmicro Please cite this article as: Ariza-Miguel, J., et al., Evaluation of two commercially available chromogenic media for confirmation of methicillin-re- sistant Staphylococcus aureus from human, animal..., Int. J. Food Microbiol. (2015), http://dx.doi.org/10.1016/j.ijfoodmicro.2015.05.004