Detection and characterization of Clostridium botulinum isolated from powdered infant formula.

INTRODUCTION

As a part of an ongoing investigation of the 2025 multistate outbreak of infant botulism linked to consumption of powdered infant formula (PIF), various samples - including unopened containers of PIF and base powder (bulk PIF before packaging) - were analyzed for the presence of Clostridium botulinum.

METHODS

Samples were screened using a tiered analytical approach: anaerobic enrichment followed by real-time PCR targeting botulinum neurotoxin-associated genes, confirmatory PCR, amplicon sequencing, colony isolation, and whole-genome sequencing (WGS). C. botulinum was detected in both the finished product and base powder.

RESULTS

Genomic analysis revealed genetic identity between isolates from one finished product lot and a base powder, while an isolate from another lot was distinct. Importantly, detection occurred in samples with non-detectable sulfite-reducing clostridia (SRC).

CONCLUSION

Results of this study demonstrate that indicator-based screening (such as SRC enumeration) even if it had been in place before the outbreak, would not have prevented its occurrence. Positive linkage of an infant botulism outbreak to PIF should compel manufacturers to recognize C. botulinum as a hazard reasonably likely to occur in certain ingredients, necessitating the design and implementation of specific preventative controls.