Antimicrobial resistance in Salmonella that caused foodborne disease outbreaks: United States, 2003-2012

Although most non-typhoidal Salmonella illnesses are self-limiting, antimicrobial treatment is critical for invasive infections. To describe resistance in Salmonella that caused foodborne outbreaks in the United States, we linked outbreaks submitted to the Foodborne Disease Outbreak Surveillance System to isolate susceptibility data in the National Antimicrobial Resistance Monitoring System. Resistant outbreaks were defined as those linked to one or more isolates with resistance to at least one antimicrobial drug. Multidrug resistant (MDR) outbreaks had at least one isolate resistant to three or more antimicrobial classes. Twenty- one per cent (37/ 176) of linked outbreaks were resistant. In outbreaks attributed to a single food group, 73% ( 16/ 22) of resistant outbreaks and 46% (31/ 68) of non- resistant outbreaks were attributed to foods from land animals (P < 0.05). MDR Salmonella with clinically important resistance caused 29% (14/ 48) of outbreaks from land animals and 8% (3/ 40) of outbreaks from plant products (P < 0.01). In our study, resistant Salmonella infections were more common in outbreaks attributed to foods from land animals than outbreaks from foods from plants or aquatic animals. Antimicrobial susceptibility data on isolates from foodborne Salmonella outbreaks can help determine which foods are associated with resistant infections.