# Establishing a Rapid Enrichment Medium for Bacillus cereus to Shorten Detection Time

## TL;DR

This paper develops a new medium to quickly detect Bacillus cereus in food, reducing detection time from 48 to 6 hours.

## Contribution

A novel rapid enrichment medium (BC-TSB) is developed to shorten detection time and improve accuracy for Bacillus cereus.

## Key findings

- BC-TSB medium significantly promotes B. cereus growth and spore germination while inhibiting non-target bacteria.
- BC-TSB achieves an 87% recovery rate of thermally injured B. cereus cells in 6 hours.
- BC-TSB enables 100% detection of B. cereus in various milk types using traditional and PMAxx-qPCR methods.

## Abstract

Bacillus cereus is a common Gram-positive bacterium that poses a significant threat to food safety due to its environmental adaptability, spore-forming ability, and production of harmful toxins. Traditional detection methods for B. cereus are time-consuming and inaccurate. This study aimed to develop a rapid enrichment medium for B. cereus to improve detection efficiency. Five B. cereus strains and five non-B. cereus strains were used. The TSB medium was selected as the basic medium as it supported the best growth and spore germination of B. cereus among the tested media. Magnesium sulfate and inosine were identified as the most effective promoters for the growth of vegetative cells and spore germination respectively, while glycine and sodium nitrite were chosen as suitable inhibitors against non-B. cereus bacteria. Through orthogonal experiments, the optimal formulation of the rapid enrichment medium (BC-TSB) was determined. BC-TSB effectively inhibited the growth of non-target bacteria and significantly promoted the growth and spore germination of B. cereus compared to the TSB basic medium. It also efficiently facilitated the recovery of thermally injured B. cereus cells, with a 6 h recovery rate of 87%—shortening the incubation time required by traditional method from 48 h to 6 h. In the detection of artificially contaminated dairy samples, BC-TSB could effectively pre-enrich B. cereus, achieving a 100% detection rate in UHT milk, modified milk, and pasteurized milk using both traditional and PMAxx-qPCR methods. Overall, the developed BC-TSB medium has great potential for the rapid and accurate detection of B. cereus in food, which can help enhance food safety monitoring.