When Krystina Brugh fell ill in January, her parents thought it was the stomach flu. They fed her crackers and her favorite sandwich, peanut butter and marshmallow fluff, to give her strength.

She didn't get better. Soon, the 11-year-old couldn't even keep down water, and her kidneys started to fail.

Krystina's parents believe they know the cause of her illness — salmonella-contaminated peanut butter — and on Thursday, they filed a federal lawsuit against foodmaker ConAgra Foods Inc. They are seeking unspecified damages.

"She's tired of the illness, she's also tired herself," said Krystina's mother, Christina. "She's not got the energy like she used to."

Omaha, Neb.-based ConAgra recalled all its peanut butter in February after government investigators linked an outbreak of salmonella to the company's Peter Pan and Great Value brands. More than 600 people in 47 states reported becoming ill, and the company faces lawsuits in several states.

ConAgra spokeswoman Stephanie Childs said she couldn't comment on the Brughs' lawsuit, filed in U.S. District Court for the Northern District of Indiana, because she hasn't seen it.

"Any consumer that may have been made ill or harmed by our product is of deep concern to us," she said. "We do take consumer safety and health very seriously. It's why we initiated the recall as quickly as we could."

Krystina had been eating Peter Pan peanut butter from a jar that had a product code starting with the number 2111, the lawsuit states. In February, the U.S. Food and Drug Administration advised people to avoid jars bearing that code due to the salmonella risk.

The warning came too late for Krystina, who has been on dialysis for five months, her parents said. Her illness has forced her parents to miss work, and medical costs are adding up. On Monday, she is set to receive a kidney from her father.

"I just set my bills aside right now because I'm more concerned about my daughter and her surgery," her mother said.

Christina and John Brugh Jr. say they want the government to do more to test food and make it safer.

ConAgra plans to reintroduce Peter Pan to store shelves in July and is having another company make it until factory renovations are complete, Childs said.

Company officials have said they can't be certain what caused the contamination. They believe moisture in the company's peanut butter plant likely helped salmonella bacteria grow. They say the salmonella likely came from raw peanuts.