Original Articles Resistance to Sulfonamides and Dissemination of sul Genes Among Salmonella spp. Isolated from Food in Poland Lukasz Ma ˛ ka, 1 El _ zbieta Mac ´ kiw, 1 Halina S ´ cie _ zyn ´ ska, 1 Magdalena Modzelewska, 1 and Magdalena Popowska 2 Abstract Antimicrobial resistance of pathogenic bacteria, including Salmonella spp., is an emerging problem of food safety. Antimicrobial use can result in selection of resistant organisms. The food chain is considered a route of transmission of resistant pathogens to humans. In many European countries, sulfonamides are one of the most commonly used antimicrobials. The aim of our investigation was to assess the prevalence of sul genes and plasmid occurrence among sulfonamide-resistant Salmonella spp. Eighty-four sulfonamide-resistant isolates were collected in 2008 and 2013 from retail products in Poland. Minimal inhibitory concentration of all of these isolates was ‡ 1024 lg/mL. Resistant isolates were tested for the presence of sul1, sul2, sul3, and int1 genes by using multiplex polymerase chain reaction. In total, 44.0% (37/84) isolates carried the sul1 gene, 46.4% (39/84) were sul2 positive, while the sul3 gene was not detected in any of the sulfonamide-resistant isolates tested. It was found that 3.6% (3/84) of resistant Salmonella spp. contained sul1, sul2, and intI genes. All 33 intI-positive isolates carried the sul1 gene. Eleven of the sulfonamide-resistant isolates were negative for all the sul genes. Most of the sulfonamide-resistant Salmonella spp. harbored plasmids; only in eight isolates were no plasmids detected. Generally, the size of the plasmids ranged from approximately 2 kb to ‡ 90 kb. Our results revealed a relatively a high prevalence of sulfonamides-resistant Salmonella spp. isolated from retail food. Additionally, we have detected a high dissemination of plasmids and class 1 integrons that may enhance the spread of resistance genes in the food chain. Introduction S almonella spp. are some of the most common human foodborne pathogens in the European Union (EU). A total of 92,916 salmonellosis cases were reported by the 27 EU member countries in 2012 (EFSA and ECDC, 2014). The 2 most commonly reported Salmonella serovars in 2012, of all confirmed cases in humans, were Salmonella Enteritidis (41.3%) and Salmonella Typhimurium (22.1%). In Poland in 2012, a total of 8444 salmonellosis cases were reported, in- cluding 8267 cases of food poisoning. The most frequently isolated serotype was Salmonella Enteritidis (75.2%), while the second was Salmonella Typhimurium (6.6%) (Czar- kowski et al., 2013). Humans are infected via the contami- nated food, mainly chicken, dairy products, and eggs. Antimicrobial resistance of pathogenic bacteria is an emerging problem. According to official documents, about 25,000 patients die each year in the EU, Iceland, and Norway from infections with antibiotic-resistant bacteria. Infections from resistant bacteria result in annual costs of at least EUR 15 billion in the EU due to additional healthcare and loss of productivity (ECDC/EMEA, 2009). Resistance among foodborne pathogens is linked to use of antimicrobials in animals (Phillips et al., 2004). Sulfo- namides are one of the most commonly used antimicrobials. In total, 17% of the sales of veterinary antibacterial agents in the 10 European countries were sulfonamides and tri- methoprim (as sulfonamides or in combination) (Grave et al., 2010). Sulfonamides exhibit bacterial activity against many aerobic bacteria, usually used in combination with trimethoprim. In human medicine, sulfonamides may be utilized in gastrointestinal infections or urinary tract in- fections, and in animals they may also used in therapy of the respiratory system. 1 Laboratory of Food Microbiology, Department of Food Safety, National Institute of Public Health—National Institute of Hygiene, Warsaw, Poland. 2 Department of Applied Microbiology, Institute of Microbiology, Faculty of Biology, University of Warsaw, Warsaw, Poland. FOODBORNE PATHOGENS AND DISEASE Volume 12, Number 5, 2015 ª Mary Ann Liebert, Inc. DOI: 10.1089/fpd.2014.1825 383