In the letter, the FDA said it was concerned that preterm infants were at risk of potentially fatal diseases or infections caused by bacteria or yeast contained in the probiotics. "The product is an unapproved new drug and an unlicensed biological product being sold in violation" of regulations, the FDA said on Thursday about Abbott's Similac probiotic product. Infinant's product, sold under the brand Evivo with MCT Oil, has since been voluntarily recalled and is no longer available in the country, the FDA said.