[W7] Food and water borne infections

Question 1

What is the difference between infection and intoxication?

Answer 1

Infection: Pathogen proliferates in the host. Intoxication: Disease is caused by ingested toxins, not direct pathogen action.

Question 2

How are foodborne and waterborne diseases transmitted?

Answer 2

Foodborne: Via contaminated food. Waterborne: Via contaminated drinking or environmental water.

Question 3

What organism causes typhoid fever?

Answer 3

Salmonella enterica subsp. enterica serovar Typhi (S. Typhi).

Question 4

How does typhoid spread?

Answer 4

Fecal-oral route through contaminated food or water.

Question 5

What are the symptoms of typhoid?

Answer 5

Fever, vomiting, headache, rapid heart rate, fluctuating temperature.

Question 6

What is the incubation period and progression of typhoid?

Answer 6

1 week incubation → 1 week of symptoms → recovery, carrier state, or death.

Question 7

What is the fatality rate of untreated typhoid?

Answer 7

Around 30%.

Question 8

What makes S. Typhi different from non-typhoidal strains?

Answer 8

• Human-specific
• Causes systemic disease
• Encapsulated with Vi capsule
• Can enter a carrier state

Question 9

What is the function of the Vi capsule?

Answer 9

• Prevents phagocytosis
• Avoids IgM binding
• Engages DC-SIGN receptors on macrophages
• Induces anti-inflammatory IL-10

Question 10

Where does S. Typhi persist in carriers?

Answer 10

Gallbladder, liver, spleen – often associated with gallstones and biofilms.

Question 11

What is Campylobacter jejuni?

Answer 11

A Gram-negative, spiral-shaped, microaerophilic bacterium; leading cause of bacterial gastroenteritis worldwide.

Question 12

What are the symptoms of campylobacteriosis?

Answer 12

• Fever, headache, muscle pain
• Diarrhoea (often bloody)
• Abdominal pain and cramps
• Duration: 2–10 days

Question 13

What is the treatment for Campylobacter infection?

Answer 13

Generally self-limiting; rehydration is key. Antibiotics used only in severe cases.

Question 14

How is Campylobacter transmitted?

Answer 14

• Contaminated chicken (70% UK supermarket chicken is positive)
• Cross-contamination during food prep
• Contaminated water or unpasteurized milk
• Wild bird feces

Question 15

Why should you not wash raw chicken?

Answer 15

Increases risk of kitchen contamination via splash.

Question 16

What is the economic burden of Campylobacter in the UK?

Answer 16

Approximately £500 million per year.

Question 17

What is GBS?

Answer 17

Acute immune-mediated neuropathy causing tingling, weakness, and paralysis.

Question 18

How does C. jejuni trigger GBS?

Answer 18

• Lipooligosaccharides (LOS) mimic GM1 gangliosides
• Immune cross-reaction → myelin damage

Question 19

What is the incidence of GBS after C. jejuni infection?

Answer 19

Approximately 1.17 per 1000 cases.

Question 20

What is C. botulinum?

Answer 20

Gram-positive, spore-forming, obligate anaerobe; produces botulinum neurotoxin.

Question 21

What causes botulism disease?

Answer 21

Ingestion of pre-formed toxin (not the bacteria).

Question 22

Where does the botulinum toxin accumulate?

Answer 22

Improperly sterilized canned foods or anaerobic environments.

Question 23

What are the types of botulism?

Answer 23

• Foodborne: Pre-formed toxin in food
• Wound: Toxin release from infected wounds
• Infant: Toxin produced in the gut (e.g. via honey or soil exposure)

Question 24

What are early symptoms of foodborne botulism?

Answer 24

• Weakness in cranial nerve-fed muscles: eyes, face, jaw
• Descending paralysis
• Postural hypotension
• Respiratory failure (severe cases)

Question 25

What is 'floppy baby syndrome'?

Answer 25

Infant botulism presenting with constipation, lethargy, weak cry, flaccid paralysis.

Question 26

How is infant botulism treated?

Answer 26

Ventilation, fluids, and BabyBIG antitoxin.

Question 27

What is the mortality rate of infant botulism with treatment?

Answer 27

Around 7%.