Highly resistant Salmonella Newport-MDRAmpC transmitted through the domestic US food supply:: A FoodNet case-control study of sporadic Salmonella Newport infections, 2002-2003

Background. A new multidrug-resistant ( MDR) strain of Salmonella serotype Newport, Newport-MDRAmpC, has recently emerged. We sought to identify the medical, behavioral, and dietary risk factors for laboratory-confirmed Salmonella Newport infection, including that with Newport-MDRAmpC. Methods. A 12-month population-based case-control study was conducted during 2002 - 2003 in 8 sites of the Foodborne Diseases Active Surveillance Network ( FoodNet), with 215 case patients with Salmonella Newport infection and 1154 healthy community control subjects. Results. Case patients with Newport-MDRAmpC infection were more likely than control subjects to have taken an antimicrobial agent to which Newport-MDRAmpC is resistant during the 28 days before the onset of diarrheal illness ( odds ratio [ OR], 5.0 [ 95% confidence interval {CI}, 1.6 - 16]). Case patients with Newport-MDRAmpC infection were also more likely to have eaten uncooked ground beef ( OR, 7.8 [ 95% CI, 1.4 - 44]) or runny scrambled eggs or omelets prepared in the home ( OR, 4.9 [ 95% CI, 1.3 - 19]) during the 5 days before the onset of illness. International travel was not a risk factor for Newport-MDRAmpC infection but was a strong risk factor for pansusceptible Salmonella Newport infection ( OR, 7.1 [ 95% CI, 2.0 - 24]). Case patients with pansusceptible infection were also more likely to have a frog or lizard in their household ( OR, 2.9 [ 95% CI, 1.1 - 7.7]). Conclusions. Newport-MDRAmpC infection is acquired through the US food supply, most likely from bovine and, perhaps, poultry sources, particularly among persons already taking antimicrobial agents.