The article documents a 1998 outbreak of DT 104 in Denmark.[1] Twenty-one adults and children were identified as having acquired the disease directly or indirectly through contaminated pork. By the time the outbreak was over, 7 had been hospitalized and 1 had died.

The outbreak came to light in June of 1998 after five patients were identified as having an unusual strain of salmonella food poisoning. On the same day that this particular strain was identified, the Danish national salmonella surveillance program identified the same strain of salmonella in pork samples collected from a slaughterhouse in late May. Using molecular "fingerprinting" techniques, scientists traced the spread of this new multidrug-resistant strain of salmonella from pigs to humans (see the diagram). Following one lead after another, they sampled nearly 90 herds of swine. In the end, two herds tested positive: one herd in the process of fattening and a second herd that had delivered piglets to and shared machinery with the farm with the first herd.

A Foodborne Disease Outbreak Affects People Throughout the Community

Using modern molecular techniques, researchers in Denmark were able to reconstruct the course of the 1998 Salmonella DT-104 outbreak from the farm through the community.

The tracing of this salmonella outbreak through the food chain provides an important opportunity to study how diseases that originate on the farm spread through a community. As might be expected, the largest group of victims consisted of people who ate contaminated pork products. But others were also infected. One of the victims worked at the incriminated slaughterhouse. Two more people probably acquired the disease through exposure to one of the hospitalized victims. A nurse became ill after attending to this patient, while a woman recovering from complications of cancer therapy also fell ill after sharing a room with the same person. The 82-year-old woman later died. So simply changing what we eat is not necessarily enough to protect ourselves from an outbreak of an infectious disease like salmonella.

This study has another ominous implication for public health. In addition to DT 104's resistance to five important antibiotics, this strain is now reported becoming resistant to a group of antibiotics called fluoroquinolones -- drugs of first choice for fighting serious salmonella infections. Doctors in this study reported a reduced effectiveness of fluoroquinolone drugs when treating patients during this outbreak. Although it was not possible to directly link the development of resistance in the salmonella to fluoroquinolone use on the swine farms, the practice is a plausible cause. While quinolone drugs had not been used in the two herds that year, the drugs had been used on nearby farms and salmonella is thought to move easily between herds. In Denmark, veterinarians have been licensed to use fluoroquinolones since 1993.

DT 104 is a problem in the United States too. Over the past few years, reports of reduced effectiveness of the fluoroquinolone drugs against Salmonella DT 104 have increased substantially. Outbreaks of the multi-antibiotic-resistant DT 104 strain have recently occurred in California, Vermont, and Washington State. The Centers for Disease Control and Prevention reports that salmonella poisoning (all strains) may affect up 2 million people annually in the United States and that about 500 of these die each year.

Note

Sources

D. Ferber, 2000. Antibiotic Resistance: Superbugs on the Hoof? Science, 288. May 5, pp. 792-794.

K. Mølbak, et al., 1999. An Outbreak of Multidrug-Resistant, Quinolone-Resistant Salmonella enterica Serotype Typhimurium DT104. The New England Journal of Medicine, 341(19), pp. 1420-1425.