Antimicrobial resistance determinants in antibiotic and biocide- resistant gram-negative bacteria from organic foods Miguel Ángel Fernández Fuentes, Elena Ortega Morente, Hikmate Abriouel, Rubén Pérez Pulido, Antonio Gálvez * Área de Microbiología, Departamento de Ciencias de la Salud, Facultad de Ciencias Experimentales, Universidad de Jaén, 23071 Jaén, Spain article info Article history: Received 27 March 2013 Received in revised form 21 August 2013 Accepted 27 August 2013 Keywords: Gram-negative bacteria Organic foods Antimicrobial resistance genes Efflux pumps abstract In the present study, a collection of 29 Gram-negative bacteria selected from organic foods according to antibiotics and biocide resistance were screened for multidrug efflux pumps and specific antibiotic resistance genes. The acrB pump gene of the AcrABeTolC system was detected in all isolates. EfrAB determinants efrA and efrB were frequently detected (Enterobacter, Pantoea, Salmonella), while other efflux pump genes (norE, mepA mdeA, norC) were detected only in some Enterobacter and Pantoea iso- lates. Genes encoding resistance to quaternary ammonium compounds qacE and qacJ were detected only in Enterobacter isolates, while sugE was detected in Enterobacter and in one Pantoea isolate. The aminoglycoside-resistance ant(4_)-Ia gene was detected in Enterobacter, Pantoea agglomerans and Kleb- siella oxytoca. The antibiotic resistance determinant most frequently found was lsa gene (Enterobacter, Pantoea and Salmonella isolates). Erythromycin resistance genes (ereA, ereB) were detected among Enterobacter, Klebsiella or Salmonella. The macrolide efflux pump msrA and the phosphotransferase type I mphA genes were detected in Salmonella. Other resistance determinants analyzed (mdfA, yhiUV, evgA, 455emeA, yvcC, qacA/B, qacC, qacG, qacH, norA, norB, norC, sdrM, sepA, mecA, emrE, smr, bla, cat, aac(6_)-Ie- aph(2_)-Ia, aph(2_)-Ib, aph(2_)-Ic, aph(2_)-Id, aph(3_)-IIIa, ermA, ermB, ermC, and mefA genes) were not detected in any isolate. Results from the present study suggest that the main mechanisms of antibiotic and biocide resistance in Gram-negative bacteria from organic foods rely on different kinds of efflux pumps of broad substrate specificity. The indiscriminate use of biocides in the food chain should be revised in order to minimize persistence of reservoirs of antimicrobial resistance in the food chain. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction The market for organic food is growing worldwide. In parallel to the process-related quality criteria such as environmental issues and animal welfare, product criteria such as taste, nutrition and health, as well as organic specific indicators are becoming more and more important (Kahl, 2012). However, less is known about the safety of organic foods compared to those obtained by conventional methods, particularly regarding the presence of antibiotic resis- tance elements in bacteria from these foods. The fact that bacterial enteropathogens of animal origin can spread in nature and persist in the phyllosphere (DuPont, 2007; Heaton & Jones, 2008) has raised concerns about possible role of organic foods in the spread of antimicrobial resistance. Over the past two decades, antimicrobial resistance among Enterobacteriaceae has so dramatically escalated worldwide that this family has supplanted Gram-positives in terms of frequent resistant bacteria seen in the outpatient setting (Lynch, Clark, & Zhanel, 2013). Antimicrobial resistance genes can rapidly move through bacterial populations and emerge in pathogenic bacteria via horizontal gene transfer (Wright, 2012). Clonal spread of resistant organisms among hospitals, geographic regions and continents has fueled the explo- sive rise in resistance (Nordmann, Naas, & Poirel, 2011). Clones of multidrug resistant (MDR) bacteria have globally disseminated, and in some cases, infections are essentially untreatable with existing antimicrobial agents. In fact, over the last few years several studies have documented the emergence of antibiotic resistance in Enter- obacteriaceae (Livermore, 2012; Lynch et al., 2013). Outbreaks of bla (VIM-1-positive) carbapenem-resistant Klebsiella pneumoniae (CRKP) and K. pneumoniae carbapenemase 2 (KPC2)-producing K. pneumoniae have been reported in some European countries * Corresponding author. Present address: Área de Microbiología, Departamento de Ciencias de la Salud, Facultad de Ciencias Experimentales, Edif. B3, Universidad de Jaén, Campus Las Lagunillas s/n, 23071 Jaén, Spain. Tel.: þ34 953 212160; fax: þ34 953 212943. E-mail address: agalvez@ujaen.es (A. Gálvez). Contents lists available at ScienceDirect Food Control journal homepage: www.elsevier.com/locate/foodcont 0956-7135/$ e see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.foodcont.2013.08.041 Food Control 37 (2014) 9e14