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Isolation and Characterization of Bacillus cereus Group Species in Powdered Infant Formula and Infant Cereal Using a
Paul Tuan Nguyen1, Tyler Chandross-Cohen2, Jasna Kovac2
1R & F Products, Inc., 2725 Curtiss Street Downers Grove, IL 60515, USA.
Insights
A new detection method effectively identified low levels of Bacillus cereus group bacteria in infant foods. This ensures the safety of powdered infant formula and cereals for vulnerable infants.
Area of Science:
- Food Microbiology
- Microbial Safety
- Infant Nutrition
Background:
- Bacillus cereus group species are common in infant foods.
- Temperature abuse can lead to unsafe levels of B. cereus in these products.
- A sensitive detection method is needed to assess risk in infant foods.
Purpose of the Study:
- To develop and evaluate a detection scheme for low-level B. cereus group species in infant foods.
- To assess the virulence potential of recovered isolates.
- To ensure the safety of infant formula and cereals.
Main Methods:
- Development of the R & F® Bacillus cereus Group Enrichment Broth.
- Evaluation of a detection scheme for powdered infant formula and infant cereals.
- Whole genome sequencing and in vitro cytotoxicity assays.
Main Results:
- The detection scheme recovered B. cereus group species from 52% of samples initially below 100 CFU/g.
- A high predictive positive value (97.6%) was achieved, confirmed by whole genome sequencing.
- Cytotoxicity assays showed varying virulence levels in recovered isolates.
Conclusions:
- The enrichment method effectively detects potentially virulent B. cereus group strains in infant foods.
- Regular monitoring of these bacteria in infant foods is crucial for protecting vulnerable infants.
- Ensuring microbiologically safe infant products is paramount.
Abstract:
Bacillus cereus group species are frequently detected at low levels in infant foods, including powdered infant formula and infant cereals. Although the infectious dose in neonates and infants has not been established, evidence suggests it may be approximately 1,000 CFU/g. When infant foods are exposed to temperature abuse, B. cereus group species could grow beyond acceptable limits, resulting in microbiologically unsafe products. Therefore, a detection scheme using an enrichment broth may be necessary to assess their potential risk in these critical foods. In this study, the R & F® Bacillus cereus Group Enrichment Broth was developed, and a detection scheme was evaluated for its efficacy in recovering low-level B. cereus group species from powdered infant formula and infant cereals. Additionally, we used whole genome sequencing to gain deeper insights into the genomic characteristics of the recovered isolates and performed in vitro cytotoxicity assays to assess their virulence potential. The detection scheme recovered B. cereus group species in 52% (26/50) of samples that had initially screened below 100 CFU/g, resulting in a predictive positive value (PPV) of 97.6% as confirmed by whole-genome sequencing of the recovered isolates. Cytotoxicity testing of selected isolates revealed varying levels of toxicity toward Caco-2 cells. The results demonstrate that the enrichment method effectively recovered potentially virulent B. cereus group strains, highlighting the need for regular monitoring of these species in infant foods, especially for vulnerable populations such as premature neonates and infants.
