Highly ResistantSalmonellaNewport‐MDRAmpC Transmitted through the Domestic US Food Supply: A FoodNet Case‐Control Study of SporadicSalmonellaNewport 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.