WSQ Food-borne Pathogens — Questions and Answers
Question 1: What is Salmonella and how is it commonly transmitted in Singapore?
- A type of fish
- A bacterium commonly found in raw poultry, eggs, and meat that causes food poisoning through improper cooking or cross-contamination (Correct answer)
- A chemical contaminant
- A type of mould
Correct answer: A bacterium commonly found in raw poultry, eggs, and meat that causes food poisoning through improper cooking or cross-contamination
Salmonella is one of the most common food-borne pathogens in Singapore. It is found in raw poultry, eggs, and meat. Prevention requires thorough cooking (74°C for poultry) and preventing cross-contamination.
Question 2: What conditions do bacteria need to multiply?
- Only warmth
- Food (nutrients), Acidity (neutral to slightly acidic pH), Time, Temperature (danger zone), Oxygen (some need it, some do not), and Moisture (Correct answer)
- Only food and water
- Only darkness
Correct answer: Food (nutrients), Acidity (neutral to slightly acidic pH), Time, Temperature (danger zone), Oxygen (some need it, some do not), and Moisture
The acronym FATTOM describes what bacteria need: Food, Acidity (pH 4.6-7.5), Time (in the danger zone), Temperature (5-60°C), Oxygen (varies), and Moisture (water activity above 0.85).
Question 3: What is Staphylococcus aureus and how does it contaminate food?
- A virus found in water
- A bacterium carried on human skin, nose, and throat that contaminates food through handling; it produces heat-resistant toxins (Correct answer)
- A parasite found in fish
- A chemical found in cooking oil
Correct answer: A bacterium carried on human skin, nose, and throat that contaminates food through handling; it produces heat-resistant toxins
Staphylococcus aureus lives on human skin, in nasal passages, and on wounds. It contaminates food through handling, producing toxins that cannot be destroyed by reheating — making prevention essential.
Question 4: What is Norovirus and why is it a concern for food establishments in Singapore?
- A type of bacteria killed by cooking
- A highly contagious virus causing vomiting and diarrhoea that can spread through contaminated food, water, or surfaces; very small amounts cause illness (Correct answer)
- A mould found in bread
- A toxin in shellfish
Correct answer: A highly contagious virus causing vomiting and diarrhoea that can spread through contaminated food, water, or surfaces; very small amounts cause illness
Norovirus is extremely contagious — just 18 viral particles can cause illness. It spreads through contaminated food (especially shellfish and salads), water, surfaces, and person-to-person contact.
Question 5: How can food handlers prevent the spread of Listeria in food?
- Only through cooking
- By maintaining proper refrigeration (Listeria can grow at refrigeration temperatures), avoiding cross-contamination, and consuming ready-to-eat chilled foods within their shelf life (Correct answer)
- Listeria is not found in Singapore
- Only by using pesticides
Correct answer: By maintaining proper refrigeration (Listeria can grow at refrigeration temperatures), avoiding cross-contamination, and consuming ready-to-eat chilled foods within their shelf life
Listeria monocytogenes is unusual because it can grow at refrigeration temperatures (as low as 0°C). It is found in ready-to-eat chilled foods, soft cheeses, and deli meats. Proper stock rotation and temperature control are essential.
Question 6: What is the incubation period for most food-borne bacterial infections?
- Immediately after eating
- Typically 1-72 hours after consuming contaminated food, varying by the type of pathogen (Correct answer)
- Always exactly 24 hours
- 1-2 weeks after eating
Correct answer: Typically 1-72 hours after consuming contaminated food, varying by the type of pathogen
Incubation periods vary: Staphylococcus toxins act in 1-6 hours, Salmonella in 6-72 hours, and Listeria can take up to 70 days. This makes it challenging to identify the source food.
WSQ Food-borne Pathogens
What is Salmonella and how is it commonly transmitted in Singapore?