Microbiological hazards (Foodborne pathogens)
Bacteria
The main cause of food poisoning.
Viruses Hepatitis A
Norovirus
Viral gastroenteritis
Quite common but usually relatively mild. Often spread by the faecal/oral route and from the environment. Usually low dose. Norovirus quite common but under-reported because of relatively
mild illness for short period of time.
Protozoa
Cryptosporidium parvum
Giardia lamblia (faecal/oral route,waterborne outbreaks)
Moulds (fungi)
Aspergillus spp. produce mycotoxins
Aflatoxin (nuts)
Patulin (apple juice)
Parasites
Taenia saginata (beef)
Trichina spiralis (pork and horse flesh)
Algae
Poisonous dinoflagellates which produce biotoxins causing paralytic and diarrhetic shellfish poisoning
Sources of pathogens
People
• Hands, Nose, sneezing, Mouth, Hair, Skin cuts and grazes
• Intestines
• Sewage
Raw food/water/ice
• Red and white meat
• Raw vegetables (soil)
• Milk
• Eggs
• Shellfish (especially bivalves)
• Ready-to-eat fruit/salad vegetables
– contaminated irrigation
– poor hygiene of harvesters
– contaminated in transport (manure transported one way, lettuces the other)
NB Suspected that the outbreak of Novovirus amongst British Troops in Afghanistan resulted from sewage contamination of their drinking water.
Soil/dust
• Cover food
Animals and birds
• No access to pets etc.
Insects
• Flies, cockroaches etc. (from feet, vomit, faeces etc.)
Rodents
• Rats,mice (from feet, urine, faeces, mouths etc.)
Refuse and waste food
• Do not allow waste to accumulate
NB Norovirus – inhalation of dust from desiccated vomit and faeces may occur.
Spores
Resistant resting phase of certain bacteria, e.g. Clostridium perfringens, which protects them against adverse conditions, such as high temperatures,
chemicals and dehydration.
• Survive for many years
• Activated by cooking
• Germinate during cooling
• Unaffected by refrigeration or freezing
Toxins
Poisons produced by pathogens. They may be produced in the food or in the body after the food has been eaten. Toxins are unaffected by refrigeration or freezing.
• Exotoxins: Usually formed in food, e.g. Staphylococcus aureus. Many exotoxins are very heat resistant and boiling for long periods may be required to ensure their destruction. Normal cooking may not destroy them. Eating foods containing toxins is likely to result in food poisoning. C. perfringens produces an exotoxin in the intestine when spores are formed.
• Endotoxins: Usually produced in the body, e.g. Salmonella. Once again if sufficient toxin is present we will end up with food poisoning.