LOS ANGELES (Reuters) - U.S. food safety officials on Monday said they hope that a cluster of nine cases of Salmonella poisoning yields clues that lead them to the source of an outbreak that has sickened 277 people in 28 states.
David Acheson, director of food safety for the U.S. Food and Drug Administration, said the cluster is confined to a single geographic location and that all of the sickened individuals appeared to have eaten similar types of tomatoes.
“It’s essentially a very solid lead for us,” Acheson said, in a conference call with reporters.
Acheson and other officials declined to say whether the cluster they were referring to were nine cases reported by the Chicago Department of Health.
Those individuals reportedly ate at two restaurants from the same restaurant chain, according to published reports, which did not name the company. The FDA also declined to identify the eateries involved saying the information was confidential.
A Chicago Department of Health spokesman was not immediately available for comment.
U.S. food safety officials said they continue to believe that the outbreak is not linked to a single restaurant or grocery store chain.
McDonald’s Corp, the world’s largest restaurant chain, said over the weekend that its U.S. restaurants would resume serving tomatoes.
FDA has identified dozens of states and countries whose producers’ tomatoes are not linked to the outbreak -- primarily because they were not supplying fruit during the time when people were becoming ill.
The safe list includes California, which is now a major producer, northern Florida and Baja California in Mexico.
Health officials linked the outbreak to raw plum, Roma and round tomatoes and continue to warn consumers to avoid those tomatoes if they come from producers not yet cleared by FDA.
Investigators continue to focus on product from other parts of Mexico and Florida since they were the major tomato suppliers at the time of the outbreak. They have not seen any positive results for Salmonella, Acheson said.
Salmonella Saintpaul, the bacterial strain responsible for the current outbreak, is uncommon, according to the U.S. Centers for Disease Control which sees about 400 Saintpaul infections in humans each year.
Last year there were about 25 reported U.S. cases of Salmonella Saintpaul with the same genetic fingerprint as that seen in the current outbreak, CDC spokeswoman Lola Russell said.
The Mexican government said last week that Salmonella Saintpaul has never been found in their country.
Acheson said U.S. officials are discussing that statement and posing other outbreak-related questions to representatives from Mexico.
Salmonella bacteria are frequently the culprit for food-borne illnesses. Symptoms of infection include fever, diarrhea, nausea, vomiting and abdominal pain and generally appear within 12 hours to 72 hours of eating tainted food.
Infants, the elderly and those with weakened immune systems are more likely than others to develop severe illness.
Salmonella infections commonly result from eating food that has been contaminated by animal feces, but it is also caused by human feces.
Editing by Leslie Gevirtz