Bacillus cereus

Bacillus cereus


Morphology

  • Large gram-positive
  • Aerobic rod
  • Size: 1.0 – 1.2µm x 3.0 – 5.0 µm
  • Motile by peritrichous flagella
  • Spore forming

Serology

  • 13 somatic (“O”) antigens
  • 42 flagellar (“H”) antigens
  • Serotype H1 is dominant and contains both emetic and diarrheal strains
  • Various spore antigens identified but not useful for serotyping

Growth characteristics

  • Temperature: Growth: 5 – 50 C (optimum: 28 – 35C, generation time of ~ 20 – 60 minutes)
  • Germination: 5 – 50C in media or cooked rice
  • Concern: precooked chilled foods with long shelf lives
  • pH -4.35 – 9.3

Biochemical Identification

  • Acid from glucose 
  • Nitrate reduction
  • Tyrosine decomposition
  • Lysozyme resistant
  • Strongly beta-hemolytic (motile)
  • Weakly beta-hemolytic (non-motile)
  • Hemolytic- the breakdown of red blood cells
Diarrheal Syndrome
  • Associated with proteinaceous foods, vegetables, sauces and puddings
  • Infective dose: 105 – 107 total cells
  • Incubation period: 8 – 24 h (average of 10 -12 h)
  • Profuse watery diarrhea, abdominal pain and occasional nausea
  • Duration: 12 – 24 h, self-limiting
  • Clinical illness very similar to C. perfringens food poisoning
Emetic Syndrome
  • Associated with rice (particularly fried rice)
  • Infective dose:
  • Ingestion of heatstable enterotoxin (126C/90 min) preformed in foods containing 105 – 108 B. cereus / g
  • Incubation period: 0.5 – 5 h
  • Nausea, vomiting and occasional diarrhea
  • Duration: 6 – 24 h, self-limiting
  • Clinical illness very similar to S. aureus food poisoning

Treatment 

  • Limited to fluid replacement
Exam Question
 

Diarrheal Syndrome

  • Associated with proteinaceous foods, vegetables, sauces and puddings
  • Incubation period: 8 – 24 h (average of 10 -12 h)
  • Profuse watery diarrhea, abdominal pain and occasional nausea
  • Clinical illness very similar to C. perfringens food poisoning
Emetic Syndrome
  • Associated with rice (particularly fried rice)
  • Incubation period: 0.5 – 5 h
  • Nausea, vomiting and occasional diarrhea
  • Clinical illness very similar to S. aureus food poisoning
Don’t Forget to Solve all the previous Year Question asked on Bacillus cereus

Leave a Reply

Free Mini Course on Stomach

Mini Course – Stomach

22 High Yield Topics in Stomach

in Just 2 Hours

Submission received, thank you!

Close Window
%d bloggers like this:
Malcare WordPress Security