Outbreak of Multidrug-Resistant Salmonella enterica Serotype Typhimurium Definitive Type 104 Infection Linked to Commercial Ground Beef, Northeastern

emerged in the 1990s and is associated with greater clinical severity than pansusceptible S. Typhimurium. Although infection with DT104 is common in the United States, it is rarely associated with outbreaks. From October to December 2003, a cluster of DT104 infections with indistinguishable pulsed-field gel electrophoresis patterns was identified in the northeastern United States. Methods. A case-control study that assessed exposures compared case patients to age- and geography-matched control subjects. Information on consumer purchasing and grocery store suppliers was used to trace the implicated food to its source. Results. We identified 58 case patients in 9 states by pulsed-field gel electrophoresis. Representative isolates were phage type DT104 and were resistant to ampicillin, chloramphenicol, streptomycin, sulfamethoxazole, and tetracycline (R-type ACSSuT). Of 27 patients interviewed for the case-control study, 41 % were hospitalized (median duration of hospitalization, 4 days). Compared with 71 healthy control subjects, case patients had more medical comorbidities (matched odds ratio, 4.3; 95 % confidence interval, 1.5–12.7). Illness was associated with consuming store-bought ground beef prepared as hamburgers at home (matched odds ratio, 5.3; 95 % confidence interval, 1.9–15.3) and with eating raw ground beef (). Seven case patients (27%), but no control subjects, ate rawP .001 ground beef. Product traceback linked cases to a single large ground beef manufacturer previously implicated i