Samples Collected by FDA Test Positive for C. Botulinum in ByHeart Infant Formula Investigation

Two samples collected by the U.S. Food and Drug Administration (FDA) have tested positive for Clostridium botulinum Type A as the agency continues to investigate a multistate outbreak of infant botulism linked to ByHeart Whole Nutrition infant formula.

The FDA is investigating the outbreak, which has sickened and hospitalized 51 infants in 19 states, in collaboration with the CDC, California Department of Public Health, Infant Botulism Treatment and Prevention Program and other state and local partners. No new cases have been added to the investigation since Dec. 10, 2025. 

Product sampling and testing is being conducted by FDA, CDC, state partners and ByHeart. FDA also collected ByHeart ingredient samples for analysis as part of the investigation.

As of Jan. 23, two samples collected by FDA have tested positive for Clostridium botulinum Type A. One is a ByHeart powdered infant formula closed product sample that matches a clinical isolate from an infant included in this outbreak, according to whole genome sequencing (WGS) analysis. These samples also match two isolates of organic whole milk powder, an ingredient ByHeart uses in the production of ByHeart Whole Nutrition powdered infant formula, which were collected and tested by ByHeart. 

The second organic whole milk powder sample was collected by FDA at a processor for a supplier to ByHeart and analyzed by the New York Wadsworth Laboratory. WGS analysis showed that the Clostridium botulinum found in the sample of organic whole milk powder is a genetic match to the Clostridium botulinum detected in the finished product sample of ByHeart’s infant formula, according to analysis conducted by ByHeart.

While these results advance FDA’s understanding of the outbreak, the agency said its investigation is ongoing to determine the source of contamination.

Previously, on Dec. 23, 2025, ByHeart publicly reported positive test results for Clostridium botulinum in six of 36 samples of finished product. These six samples were taken from two batches, both included in the initial product recall.

Sample Analysis.

Sample analysis is ongoing, and results will be reported as they become available, said FDA. The detection of Clostridium botulinum in infant formula, or ingredients, is complex, and confirmation of results can take several weeks, the agency said. This in part is due to the heat-resistant spores, which require special activation before they can be detected.

Testing for C. botulinum in infant formula requires specialized testing and lab equipment. While initial screening tests are performed, a preliminary positive result requires confirmatory tests. This process can take two or more weeks for final results. There are a limited number of labs that have the specialized equipment and resources to conduct these tests, which further reduces testing capacity, said FDA. The agency said it is working with partners to improve and update these methods so results can be confirmed and compared across stakeholders more easily.  

Investigation Details.

FDA's investigation is focused on gaining a clearer understanding of contributing factors in the outbreak, the agency said. This is the first documented outbreak of botulism in the United States attributed to contaminated infant formula, and there are fundamental differences between spore-forming bacteria like Clostridium botulinum and vegetative bacteria such as Cronobacter and Salmonella, said FDA.

FDA has established the FDA’s Actions to Respond to Clostridium botulinum Illnesses Associated with Consumption of Powdered Infant Formula page to capture ongoing efforts to ensure the safety of powdered infant formula, including general information about formula safety.

All ByHeart infant formula products have been recalled, and these products should not be available for sale in stores or online. This includes all formula cans and single-serve “anywhere pack” sticks.

However, FDA continues to receive reports that recalled formula is still being found on store shelves, despite the ongoing recall of all ByHeart products. FDA said it continues to work with state partners and retailers to ensure an effective recall and immediate removal of these products from store shelves across the country.

FDA’s investigation is ongoing, and this advisory will be updated as information becomes available.