Costco and Diamond Pet Foods have been sued in connection with the dog-food Salmonella Infantis outbreak in what is believed to be the first lawsuit against the Issaquah-based company and the pet-food processor.

Costco and Diamond Pet Foods have been sued in connection with the dog-food Salmonella Infantis outbreak in what is believed to be the first lawsuit against the Issaquah-based company and the pet-food processor.

Diamond has issued a massive recall of dog food made at its Gaston, S.C., plant after Salmonella was found at the facility. At least 15 people who had contact with the contaminated food or the animals who ate it have been sickened in nine states. Earlier this week, the U.S. Food and Drug Administration said a second Diamond plant, in Meta, Mo., is being investigated after a different strain — Salmonella Liverpool — was found there.

The suit was filed this week in U.S. District Court in New Jersey by national food-safety law firm Pritzker Olsen on behalf of an infant who was hospitalized for three days after contracting Salmonella.

The baby developed severe diarrhea, fever and loss of appetite, according to the complaint. The bacteria cultured from the child was the same rare type of Salmonella found in samples of contaminated kibble recalled by Diamond. Some of the recalled products were the Kirkland brand, Costco’s private label store brand that is made by Diamond.

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According to the suit, the baby’s father had purchased one of the recalled varieties — Kirkland Signature Super Premium Healthy Weight Dog Formulated with Chicken &Vegetables — for the family dogs.

The U.S. Centers for Disease Control and Prevention has said the bacteria spreads when people come into contact with the contaminated food or with an animal that has eaten the food.