1.0 Bacillus cereus and Food Poisoning

bacillus cereus is a gram positive spore forming rod that thrives in

soil

dust

wide variety of raw ingredients allowing easy entry into the food chain

spores survive cooking and can germinate if food is cooled slowley

or held 5-50℃

spore resistance bacillus cerus

can form spores that are highly resistant to heat/ desiccation and disinfectants + survive cooking processes

germination

once food cools own and is stored improperly spores can germinate into active bacteria then multiply and produce toxins

emetic (vomitting)

linked classically to reheated rice and other starches

diarrhoea

associated wth protein rich dishes such as meats. milk. vegetables and sauces

B cerus produces heat resistance endospores that germinate between up to 50℃

giving the organism a competitive advantage in improperly stored foods

thick peptidoglycan cell wall

hallmark of gram positive rod, provides rigidity and retains crystal violet stain

nucerous flagella

confer strong motility helping bacterium reach nutrients on food surfaces and colonise host tissue

plasmid carrying ces (cereulide toxin gene)

extra chromosomal DNA encoding the heat acid stable emetic toxin

Enterotoxins Hbl, Nhe, CytK

secreted pore‑forming proteins that disrupt intestinal epithelia, leading to watery diarrhoea.

Emetic illness results from ingestion of pre‑formed cereulide (bac)

• The toxin resists heat and gastric acid,

• directly stimulates vagal afferents

• and serotonin (5‑HT₃) receptors,

• and produces nausea

• and forceful vomiting within 30 minutes - 6 hours after ingestion.

vagal afferents

sensory nerve fibres that transmit information from the body’s internal organs to the brain via the vagus nerve

Diarrhoea illness follows ingestion of spores/vegetative cells that germinate in the small intestine.

The incubation time is slower than the emetic toxins with symptoms occurring 6-15 hours after ingestion.

Locally produced enterotoxins Hbl, Nhe and CytK create inflammation within small intestine

and promote electrolyte and water loss. 

Emetic illness signs + symptoms begin within 30 minutes to 6 hours and usually resolved within 12 hours.

 Abrupt nausea

and repetitive vomiting,

sometimes abdominal cramps;

diarrhoea is absent or mild.

Diarrhoea illness Symptoms begin within  6 - 15  hours and usually resolve within 24 hours

Watery diarrhoea,

abdominal pain

and cramping with occasional nausea.

Diagnosis of B. cereus

involves identifying the bacteria in samples like food, vomit, or stool, and sometimes in blood or other body fluids for non-foodborne illnesses. 

food poisoning confirmation often requires culturing the bacteria from suspect food and patient samples

along with potentially testing for the toxins produced.