Salmonella

Salmonella are a group of bacteria that can cause food poisoning. Typically, food poisoning causes gastroenteritis - an infection of the gut (intestines) which leads to diarrhoea and being sick (vomiting). Salmonella bacteria may be found in the gut of many animals, including farm animals and pets. Poultry (chickens, turkeys, etc) are especially likely to carry salmonella. So, salmonella can contaminate meat (including poultry), eggs, milk and other dairy products that we may eat. Infection usually causes relatively mild symptoms but complications, including lack of fluid in the body (dehydration), can occur in some cases. The usual treatment is to drink plenty of fluids to avoid dehydration. Antibiotic medicines are sometimes needed in some cases. The Foods Standards Agency in the UK has identified the '4 Cs' to help prevent food poisoning, including food poisoning caused by salmonella.

Salmonella are a group of bacteria that can cause food poisoning. Food poisoning occurs when food or water contaminated with germs (microbes), poisons (toxins) or chemicals is eaten or drunk. Microbes include bacteria, viruses and parasites. Parasites are living things (organisms) that live within, or on, another organism. Typically, food poisoning causes an infection of the gut (intestines), called gastroenteritis. This infection leads to to diarrhoea and being sick (vomiting).

There are over 2,500 different strains (subtypes) of salmonella. 

One type of salmonella, Salmonella typhi (S. typhi), can cause typhoid fever. This is a serious disease which can be life-threatening if not treated quickly with antibiotic medicines. It causes diarrhoea at first and then high temperature (fever), headache, stomach cramps, skin rash, feeling sick (nausea) and loss of appetite.

Another type of salmonella, Salmonella paratyphi (S. paratyphi), can cause paratyphoid fever. This is a similar illness to typhoid fever but symptoms are generally milder. Typhoid and paratyphoid are almost exclusively caught abroad in countries with poor sanitation. It can be passed on in the stools (faeces) and in the urine of infected people. Infection with S. typhi and S. paratyphi causing typhoid fever and paratyphoid fever is uncommon in the UK. Infection with various other strains is quite common.

The rest of this leaflet is only about food poisoning caused by strains of salmonella other than S.typhi and S. paratyphi.

Salmonella germs (bacteria) may be found in the gut of many animals, including wild animals, farm animals and pets. Poultry (hens, chickens, turkeys, etc) are especially likely to carry salmonella. So, salmonella can contaminate meat (including poultry), eggs, milk and other dairy products that we may eat.

Adequate cooking of meat (including poultry) usually kills salmonella bacteria. Humans can become infected if they eat undercooked meat that is contaminated with salmonella. Eating raw or undercooked eggs, or consuming milk or other dairy products contaminated with salmonella can also pass on salmonella infection to humans.

Sometimes, other foods such as fruit and vegetables can become contaminated with salmonella through contact with manure used to help them grow. Shellfish may also become contaminated if they are in contact with infected sewage in the water.

Dogs, cats and rodents can sometimes become infected with salmonella and tortoises and terrapins are also common salmonella carriers. Contact with infected animals or their stools (faeces) can also allow transmission of infection to humans. The bacteria can pass from your hands into your mouth and then your gut (intestines) where they can then multiply and cause symptoms.

Once you have salmonella, you may also spread the infection to your close contacts if you do not follow strict hygiene measures to prevent the spread of infection to others (see below).

Salmonella food poisoning is quite common. It can affect anyone of any age. In most cases it does not cause severe symptoms. However, there are certain groups of people who are more likely to develop severe symptoms. They include:

  • Young children
  • The elderly
  • People whose immune systems are not working properly (for example, people undergoing treatment for cancer, people on long-term steroid treatment, people with AIDS, etc)

Because it is possible for salmonella to be spread from person to person, outbreaks can occur, particularly in institutions such as elderly care or nursing homes.

The typical symptoms are diarrhoea and stomach cramps. The diarrhoea can sometimes be bloody. You may also feel sick (have nausea) and be sick (vomit) and you can develop a high temperature (fever). Symptoms tend to come on within 12-72 hours of eating the contaminated food or being in contact with the infected animal. This time period before symptoms appear is known as the 'incubation period'.

In most people, symptoms are relatively mild and improve within 4-7 days without any specific treatment. However, sometimes, symptoms can be more severe and/or complications can occur. If symptoms are severe, a lack of fluid in the body (dehydration) can occur. You should consult a doctor quickly if you suspect that you or your child are becoming dehydrated. Mild dehydration is common and is usually easily reversed by drinking lots of fluids. Severe dehydration can be fatal unless quickly treated because the organs of your body need a certain amount of fluid to function.

Symptoms of dehydration in children

  • Symptoms of dehydration in children include passing little urine, a dry mouth, a dry tongue and lips, fewer tears when crying, sunken eyes, weakness, and being irritable or lacking in energy (lethargic).
  • Symptoms of severe dehydration in children include drowsiness, pale or mottled skin, cold hands or feet, very few wet nappies, and fast (but often shallow) breathing. This is a medical emergency and immediate medical attention is needed.

Dehydration is more likely to occur in:

  • Children under the age of 1 year (and particularly those under 6 months old). This is because babies don't need to lose much fluid to lose a significant proportion of their total body fluid.
  • Children under the age of 1 year who were a low birth weight and who have not 'caught up' with their weight.
  • An infant who has stopped breast-feeding during their illness.
  • Any child who does not drink much when they have salmonella infection.
  • Any child with severe diarrhoea and vomiting (particularly if they have passed six or more diarrhoeal stools and/or vomited three or more times in the previous 24 hours).

Symptoms of dehydration in adults

  • Symptoms of dehydration in adults include tiredness, dizziness or light-headedness, headache, muscular cramps, sunken eyes, passing little urine, a dry mouth and tongue, weakness, and becoming irritable.
  • Symptoms of severe dehydration in adults include profound loss of enthusiasm (apathy), weakness, confusion, rapid heart rate, coma, and producing very little urine. This is a medical emergency.

Dehydration in adults is more likely to occur in:

  • Elderly or frail people.
  • Pregnant women.
  • People with severe diarrhoea and vomiting. In particular, if you are not able to replace the fluid lost with sufficient drinks.

Many people will recognise food poisoning from their typical symptoms and, if these symptoms are mild, they do not usually need to seek medical advice or receive specific medical treatment. So, you may have salmonella infection that is not 'confirmed'.

However, in some circumstances, you may need to seek medical advice when you have food poisoning (see below about when to seek medical advice). The doctor or nurse may ask you questions about recent travel abroad or any ways that you may have eaten or drunk contaminated food or water. They will also usually check you for signs of lack of fluid in the body (dehydration). They may check your temperature, pulse and blood pressure. They may also examine your tummy (abdomen) to look for any tenderness.

The doctor or nurse may ask you to collect a stool (faeces) sample. Salmonella is usually diagnosed after a sample of your stool is sent to the laboratory for testing. Food is sometimes tested for salmonella in outbreaks.

Children

If your child has gastroenteritis - an infection of the gut (intestines) which leads to diarrhoea and being sick (vomiting) - from any cause (including possible food poisoning caused by salmonella), you should seek medical advice in the following cases (or if there are any other symptoms that you are concerned about):

  • If they are under the age of 6 months.
  • If they have an underlying medical condition (eg, heart or kidney problems, diabetes, history of premature birth).
  • If they have a high temperature (fever).
  • If you suspect lack of fluid in the body (dehydration) is developing (see earlier).
  • If they appear drowsy or confused.
  • If they are being sick (vomiting) and unable to keep fluids down.
  • If there is blood in their diarrhoea or vomit.
  • If they have severe tummy (abdominal) pain.
  • Infections caught abroad.
  • If they have severe symptoms, or if you feel that their condition is getting worse.
  • If their symptoms are not settling; for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 5-7 days.
  • If you suspect that your child may have contracted food poisoning from eating restaurant or takeaway food (see below).

Adults

If you have gastroenteritis from any cause (including possible food poisoning caused by salmonella), you should seek medical advice in any of the following cases (or if there are any other symptoms that you are concerned about):

  • If you suspect that you are becoming dehydrated.
  • If you are vomiting a lot and unable to keep fluids down.
  • If you have blood in your diarrhoea or vomit.
  • If you have severe abdominal pain.
  • If you have severe symptoms, or if you feel that your condition is getting worse.
  • If you have a persisting high fever.
  • If you have a fit (seizure).
  • If your symptoms are not settling; for example, vomiting for more than 1-2 days, or diarrhoea that does not start to settle after 3-4 days.
  • Infections caught abroad.
  • If you are elderly or have an underlying health problem such as diabetes, epilepsy, inflammatory bowel disease, kidney disease.
  • If you have a weakened immune system because of, for example, chemotherapy treatment, long-term steroid treatment, HIV infection.
  • If you are pregnant.
  • If you suspect that you may have contracted food poisoning from eating restaurant or takeaway food (see below).

If you suspect that you or your child have salmonella or any other type of food poisoning from eating takeaway or restaurant food, you should report this to your local Environmental Health Office. This is so that the business can be investigated by environmental health officers and further actions may be taken if there is a problem with their food hygiene practices. This will hopefully help to reduce the chance that other people will get food poisoning. You can find your local food standards enforcer at http://www.food.gov.uk/enforcement/enforceessential/yourarea/.

If your doctor suspects that you have food poisoning, or salmonella infection is confirmed from your stool (faeces) sample, they are also required by law to report this.

Most children with salmonella do not need any specific treatment. The symptoms usually improve in a few days as their immune system has time to clear the infection. The aim is to make sure that your child has plenty of fluids to avoid a lack of fluid in the body (dehydration). Children with salmonella can usually be cared for at home. Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop. Antibiotic medicines may then be given to help clear the infection. Antibiotics may also be given in some other cases (see below).

The following are commonly advised until symptoms ease:

Fluids to prevent dehydration

You should encourage your child to take plenty of fluids. The aim is to prevent dehydration. The fluid lost in their sick (vomit) and/or diarrhoea needs to be replaced. Your child should continue with their normal diet and usual drinks. In addition, they should also be encouraged to drink extra fluids. However, avoid fruit juices or fizzy drinks, as these can make diarrhoea worse.

Babies aged under 6 months are at increased risk of dehydration. You should seek medical advice if they develop an infection of the gut (intestines), called gastroenteritis, which leads to diarrhoea and being sick (vomiting). Breast- or bottle-feeds should be encouraged as normal. You may find that your baby's demand for feeds increases. You may also be advised to give extra fluids (either water or rehydration drinks) in between feeds.

Rehydration drinks may be suggested by a healthcare professional for children at increased risk of dehydration (see above for whom this may be). They are made from sachets available from pharmacies and on prescription. You should be given instructions about how much to give. Rehydration drinks provide a perfect balance of water, salts, and sugar. The small amount of sugar and salt helps the water to be absorbed better from the gut (intestines) into the body. Home-made salt/sugar mixtures are used in developing countries if rehydration drinks are not available but they have to be made carefully as too much salt can be dangerous to a child. Rehydration drinks are cheap and readily available in the UK, and are the best treatment for your child.

If your child vomits, wait 5-10 minutes and then start giving drinks again, but more slowly (for example, a spoonful every 2-3 minutes). Use of a syringe can help in younger children who may not be able to take sips.

Note: if you suspect that your child is dehydrated, or is becoming dehydrated, you should seek medical advice.

Fluids to treat dehydration

If your child is mildly dehydrated, this may be treated by giving them rehydration drinks. Your doctor or nurse will advise about how to make up the drinks and about how much to give. The can depend on the age and the weight of your child. If you are breast-feeding, you should continue with this during this time. Otherwise, don't give your child any other drinks unless the doctor or nurse has said that this is OK. It is important that your child is rehydrated before they have any solid food.

Sometimes a child may need to be admitted to hospital for treatment if they are dehydrated. Treatment in hospital usually involves giving rehydration solution via a special tube called a 'nasogastric tube'. This tube passes through your child's nose, down their throat and directly into their stomach. An alternative treatment is with fluids given directly into a vein (intravenous fluids).

Eat as normally as possible once any dehydration has been treated

Correcting any dehydration is the first priority. However, if your child is not dehydrated (most cases) or once any dehydration has been corrected, encourage your child to have their normal diet. Do not 'starve' a child with salmonella. This used to be advised but is now known to be wrong. So:

  • Breast-fed babies should continue to be breast-fed if they will take it. This will usually be in addition to extra rehydration drinks (described above).
  • Bottle-fed babies should be fed with their normal full-strength feeds if they will take them. Again, this will usually be in addition to extra rehydration drinks (described above).
  • Older children - offer them some food every now and then. However, if he or she does not want to eat, that is fine. Drinks are the most important, and food can wait until their appetite returns.

Medication is not usually needed

You should not give medicines to stop diarrhoea to children under 12 years old. They sound attractive remedies, but are unsafe to give to children, due to possible serious complications. However, you can give paracetamol or ibuprofen to ease a high temperature (fever) or tummy (abdominal) pains.

As mentioned above, if infection is severe, antibiotics are sometimes needed. Antibiotics are also usually given to children under the age of 6 months who develop salmonella and to any child who may be malnourished or have a compromised immune system (for example, if a child is on long-term steroid treatment, is undergoing treatment for cancer, etc).

Probiotics are generally not recommended for children with gastroenteritis or food poisoning from any cause. This may change if further research shows that they are helpful.

Symptoms often settle within a few days or so as your immune system usually clears the infection. Occasionally, admission to hospital is needed if symptoms are severe, or if complications develop (see below). The following are commonly advised until symptoms ease:

Fluids - have lots to drink

The aim is to prevent lack of fluid in the body (dehydration), or to treat dehydration if it has developed. (Note: if you suspect that you are dehydrated, you should contact a doctor.)

  • As a rough guide, drink at least 200 mls after each bout of diarrhoea (after each watery stool).
  • This extra fluid is in addition to what you would normally drink. For example, an adult will normally drink about two litres a day, but more in hot countries. The above '200 mls after each bout of diarrhoea' is in addition to this usual amount that you would drink.
  • If you are sick (vomit), wait 5-10 minutes and then start drinking again, but more slowly. For example, a sip every 2-3 minutes, but making sure that your total intake is as described above.
  • You will need to drink even more if you are dehydrated. A doctor will advise on how much to drink if you are dehydrated.

For most adults, fluids drunk to keep hydrated should include water, fruit juice and soups. It is best not to have drinks that contain a lot of sugar, such as cola or pop, as they can sometimes make diarrhoea worse.

Rehydration drinks are recommended in people who are frail, or over the age of 60, or who have underlying health problems. They are made from sachets that you can buy from pharmacies. (The sachets are also available on prescription.) You add the contents of the sachet to water. Rehydration drinks provide a good balance of water, salts, and sugar. The small amount of sugar and salt helps the water to be taken up (absorbed) better from the gut into the body. They do not stop or reduce diarrhoea. As with children do not use home-made salt/sugar drinks, as the quantity of salt and sugar has to be exact.

Eat as normally as possible

It used to be advised to 'starve' for a while if you had food poisoning. However, now it is advised to eat small, light meals if you can. Be guided by your appetite. You may not feel like eating food and most adults can do without food for a few days. Eat as soon as you are able but don't stop drinking. If you do feel like eating, avoid fatty, spicy or heavy food. Plain foods such as wholemeal bread and rice are good foods to try eating.

Medication

Antidiarrhoeal medicines are not usually necessary. However, you may wish to reduce the number of trips that you need to make to the toilet. You can buy antidiarrhoeal medicines from pharmacies. The safest and most effective is loperamide. The adult dose of this is two capsules at first. This is followed by one capsule after each time you pass some diarrhoea, up to a maximum of eight capsules in 24 hours. Loperamide works by slowing down your gut's (intestinal) activity. You should not take loperamide for longer than five days.

Note: do not use antidiarrhoeal drugs if you pass blood or mucus with the diarrhoea or if you have a high temperature (fever). People with certain conditions should not take loperamide. Therefore, read the leaflet that comes with the medicine to be safe. For example, pregnant women should not take loperamide.

Paracetamol or ibuprofen are useful to ease a high temperature or headache. Antibiotic medicines may sometimes be needed to treat salmonella if the infection is severe. Doctors may also decide to give antibiotics to other groups of people including those over the age of 50, those with a weakened immune system and to those with heart valve problems. Antibiotics commonly used are called azithromycin and ciprofloxacin. Cefotaxime is another option.

If you (or your child) have salmonella, the following are recommended to prevent the spread of infection to others:

  • Wash your hands thoroughly after going to the toilet. Ideally, use liquid soap in warm running water, but any soap is better than none. Dry properly after washing. If your child wears nappies, be especially careful to wash your hands after changing nappies and before preparing, serving, or eating food.
  • If a potty has to be used, wear gloves when you handle it, dispose of the contents into a toilet, then wash the potty with hot water and detergent and leave it to dry.
  • Don't share towels and flannels.
  • Don't prepare or serve food for others.
  • If clothing or bedding is soiled, first remove any stools (faeces) into the toilet. Then wash in a separate wash at as high a temperature as possible.
  • Regularly clean with disinfectant the toilets that you use. With hot water and detergent, wipe the flush handle, toilet seat, bathroom taps, surfaces and door handles at least once a day. Keep a cloth just for cleaning the toilet (or use a disposable one each time).
  • Stay off work, school, college, etc, until at least 48 hours after the last episode of diarrhoea or being sick (vomiting). Avoid contact with other people as far as possible during this time.
  • Food handlers: if you work with food and develop diarrhoea or vomiting, you must inform your employer and immediately leave the food-handling area. If salmonella is confirmed, you should inform your employer and stay away from work until at least 48 hours after the last episode of diarrhoea or vomiting. Antibiotics are sometimes given to clear the infection.

If you have salmonella infection and you work with vulnerable groups of people such as the elderly, the unwell or the young, you should inform your employer.

Complications are uncommon in the UK. They are more likely in the very young, in pregnant women, or in the elderly. They are also more likely if you have an ongoing (chronic) condition such as diabetes or if their immune system is compromised in some way; for example, if they are taking long-term steroid medication or they are having chemotherapy treatment for cancer.

Possible complications include the following:

  • Lack of fluid in the body (dehydration) and salt (electrolyte) imbalance in your body. This is the most common complication. It occurs if the water and salts that are lost in your stools (faeces) or when you are sick (vomit), are not replaced by your drinking adequate fluids. If you can manage to drink plenty of fluids then dehydration is unlikely to occur, or is only likely to be mild, and will soon recover as you drink. Severe dehydration can lead to a drop in your blood pressure. This can cause reduced blood flow to your vital organs. If dehydration is not treated, kidney failure may also develop. Some people who become severely dehydrated need a 'drip' of fluid directly into a vein. This requires admission to hospital.
  • Reactive complications. Rarely, other parts of your body can 'react' to an infection that occurs in your gut (intestines). This can cause symptoms such as joint inflammation (arthritis), skin inflammation and eye inflammation (either conjunctivitis or uveitis).
  • Spread of infection to other parts of your body such as your bloodstream, your bones, your joints, the meninges that surround your brain and spinal cord, and your gallbladder. However, this is rare.
  • Persistent diarrhoea syndromes may rarely develop.
  • Irritable bowel syndrome is sometimes triggered by salmonella infection.
  • Lactose intolerance can sometimes occur for a period of time after infection. This is known as 'secondary' or 'acquired' lactose intolerance. Your intestinal lining can be damaged by the episode of gastroenteritis. This leads to lack of a chemical (enzyme) called lactase that is needed to help your body digest a sugar in milk, called lactose. Lactose intolerance leads to bloating, tummy (abdominal) pain, wind and watery stools after drinking milk. The condition gets better when the infection is over and the intestinal lining heals. It is more common in children.
  • Reduced effectiveness of some medicines. During any episode of food poisoning, certain medicines that you may be taking for other conditions or reasons may not be as effective. This is because the diarrhoea and/or vomiting means that reduced amounts of the medicines are taken up (absorbed) into your body. Examples of such medicines are those for epilepsy, diabetes and contraception. Speak to your doctor or practice nurse if you are unsure of what to do if you are taking other medicines and have food poisoning.

Becoming a carrier of salmonella

A 'carrier' is a person who is well, has no symptoms, but is infected with a germ (bacterium). Carriers are at risk of passing on the infection to others if their personal hygiene is not good. The vast majority of people with a salmonella infection clear the infection and bacteria completely from their body soon after symptoms ease. Rarely, on recovery from a salmonella illness, some people become carriers and continue to pass out salmonella bacteria in their stools (faeces) for weeks or months. This is more common in children. A small number of children aged less than 5 years pass out salmonella bacteria for up to a year. Over the age of 5 years, salmonella carriers are rare, and the maximum duration of shedding appears to be up to 12 weeks.

(Note: this is different to people with typhoid or paratyphoid. A small number of people who recover from these diseases remain carriers for life.)

The Foods Standards Agency in the UK has identified the '4 Cs' to help prevent food poisoning, including food poisoning caused by salmonella:

Cleanliness

  • Keep work surfaces and utensils clean.
  • Wash and dry your hands regularly but especially after going to the toilet, before preparing food, after handling raw food and before touching 'ready-to-eat' food.
  • Don't prepare food for others if you have diarrhoea or are being sick (vomiting).
  • Cover any sores or cuts on your hands with a waterproof plaster before you touch food.
  • Change dishcloths and tea towels regularly.

You should also wash your hands after touching pets or animals, after visiting farms and after gardening, to help avoid salmonella infection.

Cooking

  • Make sure that you cook food thoroughly, especially meat. This will kill bacteria. Food should be cooked right through and be piping hot in the middle.
  • If you are reheating food, it needs to be cooked right through and be piping hot in the middle.
  • Don't reheat food more than once.

You should also wash raw fruits and vegetables before you eat them. Don't drink water thought to be unsafe (including avoiding drinks containing ice cubes that may have been made from unsafe water). This includes untreated water from rivers, lakes and streams. Drink pasteurised or boiled milk and avoid raw eggs.

Chilling

  • Food that needs to be chilled or refrigerated should be. If food is left out of the fridge, bacteria may multiply to levels that can cause food poisoning.
  • Your fridge needs to be kept between 0°C and 5°C. Also, don't leave the door open unnecessarily.
  • Cool leftover food quickly and then refrigerate. Taking it out of the cooking pot and putting it into a shallow container can speed the cooling process up.

Cross-contamination

This is when bacteria pass from foods (commonly raw foods) to other foods. It can occur if foods touch directly, if one food drips on to another, if your hands, or utensils or equipment, such as knives or chopping boards, touch one food and then another.

  • Wash your hands after touching raw foods.
  • Separate raw and cooked or 'ready-to-eat' foods.
  • Keep raw meat in a sealable container at the bottom of the fridge.
  • Don't use the same surface or chopping board for preparing raw and ready-to-eat foods.
  • Make sure that knives and utensils are cleaned after preparing raw foods.

In addition to these measures, as reptiles and amphibians including terrapins and tortoises can commonly carry salmonella bacteria, you should not keep them in a house where children under the age of 1 year live, or where someone with a weakened immune system also lives.

Further help & information

Original Author:
Dr Michelle Wright
Current Version:
Peer Reviewer:
Dr Adrian Bonsall
Last Checked:
11/06/2013
Document ID:
12499 (v5)
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