Bacteria

Bacteria are microscopic (can only be seen through a microscope) living cells that are found naturally in the air, soil and water, and on work surfaces, people, animals and insects. They are around us, on us and in us everywhere and all the time. Most bacteria are harmless, we need them to stay healthy. Bacteria help our guts to digest food and are used to make many foods, such as cheese, wine, beer, yoghurt and medicines. Many of our body's bacteria fight harmful bacteria and keep us healthy.

Some bacteria are what we call pathogenic, or disease causing. Some are what we call opportunistic - in the right place and in the right numbers they are harmless or even beneficial, but in the wrong place or at the wrong numbers they can become pathogenic. Many of the 'gut bugs' or intestinal bacteria are opportunistic, they help digest food but once they get back into the food and are themselves being digested, they become pathogenic and cause illness.

Bacteria need a warm, moist environment to survive in with a food source and they may or may not need oxygen from the air to survive. If we provide these things for them, bacteria will not only survive but multiply in our food to levels where they are harmful to the person who eats that food. They multiply rapidly and can be in their billions within hours of colonising a site.

Some bacteria can survive cooking by forming spores, or protective shells around themselves, like an insulating coat. After the heat is off, they can then turn back into their normal form and begin multiplying again.

Some bacteria can also make toxins or poisons and release these into the food while they are multiplying, making the food harmful to eat. Some bacteria do not make their toxins in the food but in the person who eats them. When the bacteria-laden food gets into the person's stomach, which is acidic, they release toxins as they form spores to protect themselves from the acid, making the person sick.

Salmonella

Salmonella may be already in any meat, eggs, shellfish or raw milk as it can get there from the skin or intestine of the animal at its slaughter/milking. It doesn't make spores or toxins so it should be easy to prevent by cooking the food properly. It will be destroyed at 75-80°C. It is also likely to get into any food from the food handler not washing their hands or from utensils after handling raw meat or dairy products.

Symptoms of illness include fever, headache, abdominal pain, diarrhoea and vomiting. Illness is likely to begin 12-36 hours after eating the food and may last for up to 8 days.

Campylobacter

Campylobacter is similar to Salmonella in that it is likely to be present in meats, shellfish, raw milk and foods contaminated by the food handler. It does not make spores or toxins and can be killed at temperatures of 75-85°C. The difference is that we need a large number of salmonella bacteria in the food to make most people ill, but we only need a small number of campylobacter bacteria to make most people ill. It is also possible to get campylobacter bacteria into us from hand-to-mouth contact with an infected person. 

Symptoms of illness include fever, headache, nausea, vomiting, haemorrhagic diarrhoea and severe abdominal and muscular pain. Illness is likely to begin one to ten days after eating the food and may last between two to three days, with possible relapse.

Listeria

Listeria is an extremely common bacteria found in water, soil, plants and faeces. Foods affected by listeria are most likely to be shellfish, vegetables, raw milk and highly processed foods such as soft cheese, hams and pate. Unlike most bacteria, listeria can multiply quite happily in the fridge, but it is easily killed when cooked at temperatures of 75-80°C.

Symptoms of illness are similar to the flu and many people may not even realise they have a food-borne illness. However, the very young, very old or immunocompromised may develop the full symptoms of septicaemia or meningitis, which can kill. This also applies to unborn babies, even if an infected mother may only feel slight flu symptoms.

You may not be able to protect all your customers from Listeriosis, depending on the type of food you produce, but you should still be aware of its dangers.

Clostridium perfringens

These bacteria form spores to survive heating and produces toxins in the gut of the consumer. It is commonly found in the intestines (gut) of animals and humans and can be assumed to be present on raw meat from contamination at slaughter. It is also commonly provided by the unwashed hands of a food handler. Flies can also contaminate food with clostridium perfringens by bringing it in on dust and soil.

Controlling the time food spends between hot and cold temperatures is vital to preventing these bacteria causing harm. Assume all raw meat has the bacteria present and cook it thoroughly to kill most of them. Some may survive the cooking process thanks to their protective spores and if the cooked meat is left at room temperature for too long, these surviving bacteria will begin to multiply. Once eaten, the bacteria will release toxins to protect themselves against a person's stomach acid and make them ill. This is why it is important to serve hot food soon after cooking, ensuring it is kept above 65°C until it is eaten, or cooling it rapidly to eat cold or reheat to above 80°C. It is the time cooked food spends at room temperature that must be minimised to ensure the bacteria cannot begin to multiply in the food.

Symptoms of illness include abdominal pain and diarrhoea and may begin 6-24 hours after the food is eaten and last 12-24 hours.

Clostridium botulinum

These bacteria are another member of the clostridium family but are much more dangerous. They release their particularly poisonous toxin in the food if it is allowed to begin multiplying again at room temperature after surviving cooking by forming spores. As it is commonly found in soils and so foods likely to be affected are vegetables and filter-feeding shellfish. It has been previously associated with incorrectly preserved meats, seafood and vegetables.

Symptoms of illness include diarrhoea, then vision, breathing and speech difficulties. Fatigue, dizziness, double vision and paralysis may result, with death within one to eight days likely unless the antitoxin is given. This is one of the most toxic toxins on the planet; only a very small amount is needed to cause life threatening illness. Symptoms are likely to appear 24-72 hours after the food is eaten. Again, it is the time food spends at room temperature that allows the toxins to be produced. Bacteria growth can be prevented by ensuring the preserves are sugary, salty or acidic enough.

Staphylococcus aureas

These bacteria can only get into food from unsafe handling by the food preparer. It is commonly found in a human's nose, throat, sinuses, pimples, boils, and infected cuts and burns of the skin. It gets into the food from sneezing, coughing, dribbling or unwashed hands and skin, and then releases its toxin as it multiplies in food at room temperature.

Symptoms of illness usually appear within two to six hours of eating the food and include severe vomiting, abdominal pain, diarrhoea and collapse. Symptoms can last up to 24 hours.

Bacillus cereus

These bacteria are another spore-forming bacteria that releases toxins into food as it multiplies at room temperature. It is commonly found in soils and dusts, thus the most likely foods affected are rice, grains, vegetables and reheated meat dishes. Prevention includes ensuring that food that is not eaten straight after cooking is either kept hot at over 65°C or cooled down rapidly and chilled at below 4O°C until eaten, or thoroughly reheated to over 80°C.

Symptoms of illness include vomiting for up to five hours and/or diarrhoea for six to fifteen hours, likely to start up to fifteen hours after eating the food and lasting one to two days.

Yersinia

Yersinia is a non-spore forming bacteria that causes illness merely by its presence, similar to salmonella and campylobacter. It is commonly found in meats, seafood and water and prevention is a matter of personal hygiene of the food preparer and avoiding cross-contamination between food types.

Symptoms of illness include watery diarrhoea, intense abdominal pain, headaches, fever and vomiting. Illness is likely to begin between 24 and 36 hours after consuming the food or water, and last or up to 3 days.

E.coli

Escherischia coli is a non-spore forming and non-toxin producing opportunistic bacteria commonly found in meats, especially highly processed selections, fish, vegetables and dairy products. It is commonly found in the gut but if it gets into food, it can cause a food infection illness. There are many different types of E. coli, causing slightly different symptoms, typically vomiting and diarrhoea with abdominal cramps. Prevention is largely maintaining good personal hygiene when handling food and avoiding cross-contamination between food types. 

Symptoms are likely to begin around 18 hours after consumption of the contaminated food and last for an average of 2 days.

These illnesses can kill. In severe cases, especially in children, the elderly or immunocompromised, death by dehydration can occur. There is no excuse for illness caused by these bacteria. The required preventative measures include:

• thoroughly cooking properly thawed food to at least 80°C.
• minimising time cooked food spends at room temperature (to less than 30-60 minutes) before putting the food in a chiller kept hot until it is eaten.
• not handling food if you are ill with cold, flu or any vomiting or diarrhoea symptoms.
• washing hands thoroughly and frequently.
• washing and sanitising all utensils and equipment according to the risk of the food being prepared.
• preventing cross-contamination between food types.
• pest control.
• washing fruit and vegetables before using them.
• storing preserved foods in the fridge. 

Giardia

Giardia is a parasite found in the gut of humans and animals such as cattle, sheep, cats, dogs, rats and possums.

It is passed on in the faeces of infected animals and humans. Giardia is widespread in New Zealand and the parasites can live in the environment for long periods, especially in lakes, rivers, streams and roof water.

People become infected when they swallow the parasites. This may be from contaminated water and food, or from contact with infected animals or humans.

Cryptosporidium

Cryptosporidium is a parasite found in the gut of birds, fish, reptiles, humans and animals such as cattle, sheep, cats and dogs.

It is passed on in the faeces of infected birds, animals and humans. Cryptosporidium is widespread in New Zealand and the parasites can live in the environment for long periods, especially in lakes, rivers, streams and roof water.

People become infected when they swallow the parasites. This may be from contaminated water and food, or from contact with infected animals or humans.