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Toxigenic Potential of Mesophilic and Psychrotolerant Bacillus cereus Isolates from Chilled Tofu

Kyung-Min Park1, Hyun-Jung Kim1,2, Kee-Jai Park1

  • 1Department of Food Safety and Distribution Research Group, Korea Research Institute, Wanju-gun 55365, Korea.

Foods (Basel, Switzerland)
|June 24, 2022
PubMed

Insights

Psychrotolerant Bacillus cereus (B. cereus) in chilled tofu poses a food poisoning risk, frequently carrying more toxin genes than mesophilic strains. This highlights the need for improved control strategies against B. cereus in food.

Area of Science:

  • Food Microbiology
  • Bacterial Pathogenesis
  • Food Safety

Background:

  • Chilled tofu can harbor mesophilic and psychrotolerant Bacillus cereus (B. cereus).
  • Understanding the virulence potential of these isolates is crucial for food safety.
  • Psychrotolerant bacteria pose unique challenges due to their ability to grow at low temperatures.

Purpose of the Study:

  • To investigate the virulence potential of mesophilic and psychrotolerant B. cereus from chilled tofu.
  • To analyze toxin gene profiles, antibiograms, and biofilm formation.
  • To identify control strategies for B. cereus in the food industry.

Main Methods:

  • Isolation and characterization of B. cereus from chilled tofu.
  • Assessment of growth at low temperatures (7 °C).
  • Detection of enterotoxin genes (hemolysin BL, nonhemolytic enterotoxin complexes).
  • Antimicrobial susceptibility testing.
  • Biofilm formation assays at different temperatures.

Main Results:

  • 21 out of 58 isolates were psychrotolerant, sharing food poisoning potential with mesophilic strains.
  • Psychrotolerant B. cereus isolates more frequently harbored enterotoxin genes, with many carrying four or more.
  • Higher prevalence of hemolysin BL and nonhemolytic enterotoxin complexes in psychrotolerant isolates.
  • Some isolates exhibited resistance to rifampicin or clindamycin.
  • Mesophilic isolates showed temperature-dependent biofilm formation, unlike psychrotolerant ones.

Conclusions:

  • Psychrotolerant B. cereus in chilled tofu represents a significant food safety concern due to its virulence factors.
  • The prevalence of enterotoxin genes and biofilm formation suggests a need for targeted control measures.
  • Findings support the development of optimized technologies to inhibit B. cereus, including psychrotolerant strains, in food processing.
Keywords:
Bacillus cereusantibiogrambiofilm formationchilled tofuenterotoxin gene

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