Salmonella outbreak strikes children’s hospital

One hundred infected but source unclear

A widespread salmonella outbreak that infected 101 health care workers, patients, and visitors at St. Louis Children’s Hospital may be linked to an asymptomatic worker or a common contaminated food, investigators tell Hospital Infection Control.

The outbreak, which resulted in closure of the hospital cafeteria from June 6 to June 15, 2003, remains under investigation. "We cultured all of the food service workers, whether or not they were symptomatic," says Alexis Elward, MD, infectious disease physician at the facility. "We did find that there were some with positive cultures, including those who were asymptomatic."

Positive cafeteria workers were required to have two negative stool cultures before they could return to work.

"We cultured everybody [who worked in the cafeteria] and had them stay out of work until the final culture results were back," she says. "If their cultures were negative, they could come back to work. Of course, all of the usual criteria applied, like not working with a fever or diarrhea."

Overall, 70 health care workers, four patients, and 27 other visitors to the hospital were infected with the same strain of salmonella. There were no deaths.

"It’s all the same strain of Salmonella jadiama," she says. "Almost all of the isolates are identical by pulse-field gel electrophoresis. At least one of the later cases has a little mutation, which is characteristic of secondary transmission in an outbreak. This strain of salmonella has been associated with outbreaks in the past. There is a handful of reports in the literature about it. Previous foods that have been implicated are tomatoes, cheese, chicken, and watermelon."

To try to determine the source, Elward is conducting a case control study to identify risk factors for infection.

"We did a case control study with 105 controls and the 101 cases," she said. "We are still looking at the food to see if it was the source of the whole thing. I still don’t have any definite conclusions about the source of the outbreak."

The hospital has taken samples from more than 400 people who visited the hospital or ate in the cafeteria since May 1. The cafeteria was subjected to disinfection and cleaning before it was reopened.

"We really have just tried to reinforce existing policies," she says. "We did extra education with nutrition workers right before we reopened the cafeteria about the proper ways to handle food and to disinfect equipment."