These bacteria can be seriously dangerous for you

What is a Salmonella infection?

Salmonella infection is an infection caused by Salmonella bacteria that can lead to various illnesses such as typhoid fever, paratyphoid and intestinal inflammation. 

Transmission of the pathogens often occurs through consumption of contaminated food or via smear infection from person to person, particularly when hand hygiene is inadequate. If someone does not wash their hands thoroughly after using the toilet, tiny traces of faeces can remain on the hands. These can easily be transferred to surfaces touched by others. In this way the pathogens can enter the mouth and then the body of a new person.

Salmonella are motile, rod-shaped bacteria capable of invading human cells. There are different types of Salmonella; Salmonella typhi and Salmonella paratyphi mainly cause typhoid and paratyphoid fevers and in severe cases can lead to dangerous bloodstream infections. Salmonella enteritidis and Salmonella typhimurium typically cause vomiting and diarrhoea. 

In medical terms, infection with Salmonella bacteria is also called salmonellosis (Salmonella food poisoning). Salmonellosis is a contagious diarrhoeal disease limited to the intestinal tract (gastroenteritis). However, Salmonella infection can also have systemic effects, leading to a typhoid-like illness. 

What are the most common symptoms of a Salmonella illness?

Symptoms of a Salmonella infection usually appear within five to 72 hours after ingestion of the pathogens. The most common symptoms include: sudden onset of loose to watery diarrhoea, sometimes with blood; accompanying headaches and abdominal pain; possible nausea and vomiting, fever and fluid loss due to severe diarrhoea, which can be life-threatening especially for risk groups such as infants, young children and older people.

In rare cases, the intestinal infection can spread to other organs, causing inflammation in joints, heart, kidneys, lungs or brain. With Salmonella infections from the Enteritidis group such complications are uncommon and the illness is usually short-lived.

In typhoid fever, early symptoms are non-specific, such as headache, muscle and limb pain or cough. Body temperature rises gradually and, if untreated, can increase markedly within a few days, causing a general feeling of illness. This can initially be mistaken for influenza. In the second week diarrhoea may occur accompanied by pale red skin changes on the abdominal skin known as rose spots. Characteristic findings also include a grey-coated tongue, the so-called typhoid tongue, and an enlarged spleen. Typhoid can also lead to inflammation of other organs, intestinal bleeding, circulatory and kidney failure, and abscesses in bones and joints.

The severity of symptoms varies widely. Some people, particularly those with a strong immune system, may show no noticeable symptoms of a Salmonella infection. In medical terminology this is referred to as a “silent Salmonella infection”.

What are the consequences of a Salmonella infection?

A Salmonella infection will usually resolve without lasting damage if properly treated. The prognosis, however, depends on individual factors such as age and general health. Severe complications are more common in people with weakened immune systems, especially young children and older adults. In untreated typhoid fever the mortality rate is between 15 and 20 percent; with appropriate treatment it falls to below one percent.

Salmonella infection can lead to various complications, particularly if the body loses large amounts of fluid through vomiting and diarrhoea. This can cause a circulatory collapse, often accompanied by kidney or heart failure. Other possible consequences include intestinal bleeding, ulcers and intestinal perforations; a sudden drop in temperature during the course of the disease is a strong indication of bowel perforation.

If Salmonella enter the bloodstream, there is a risk of spread of infection to various organs, including the lungs, gallbladder, liver, bones, brain and heart. In severe cases this can lead to sepsis. Reactive arthritis, an inflammation of the joints, is another possible complication.

How long are infected people sick?

The duration of illness after a Salmonella infection varies. Typically the disease appears within 5 to 72 hours, most often after 12 to 36 hours. Adults can remain infectious for up to a month after infection, even when diarrhoea and abdominal pain subside. In young children and elderly people it can take several weeks for the bacteria to be shed, and in severe cases even six months or longer.

Which foods are more often contaminated with Salmonella?

Foods more likely to be contaminated with Salmonella include raw eggs, especially if they are not fresh or not sufficiently heated. Foods containing raw eggs also pose a high risk, e.g. ice cream, mayonnaise or raw cake batter. Salmonella enteritidis is also found in insufficiently cooked meat, particularly poultry, and in shellfish, raw milk or raw sausages such as salami or minced pork.

Cross-contamination is also possible, i.e. transfer of pathogens from contaminated foods to other products such as vegetables. It is therefore important to handle and store potentially contaminated foods separately. 

Animal-to-human Salmonella infections, for example from pets such as reptiles, are uncommon. Long-term carriers of Salmonella enteritidis who shed the bacteria without symptoms over extended periods are also rare, as these bacteria typically remain in the gut and seldom cause inflammation of other organs.

How is a Salmonella infection treated?

Treatment of Salmonella food poisoning depends on the type of pathogen, the form and the severity of the disease. Management of Salmonella enteritis presenting with sudden vomiting and diarrhoea requires careful monitoring of fluid and electrolyte balance. Patients often drink electrolyte and glucose solutions to replace lost water and salts and adjust their diet accordingly. Infants and young children receive glucose and electrolytes intravenously. Antibiotics are used in severe cases or in patients with weakened immune systems. 

In typhoid fever, Salmonella infection is treated with antibiotics such as ciprofloxacin for a period of about two weeks. Because antibiotic resistance is increasing in some regions, testing for resistance is important. After hospital discharge, patients are monitored by public health authorities until no Salmonella are detected in three consecutive stool samples.

For people who shed Salmonella long-term, antibiotic treatment is continued, often with ciprofloxacin or ceftriaxone. In small intestinal shedders lactulose is frequently used as an adjunct. In rare cases where Salmonella has colonised the gallbladder, surgical removal may be necessary.

How to prevent a Salmonella infection: effective tips

• Long-term Salmonella carriers and acutely ill people should follow special hygiene measures and should not work in contact with food, particularly in communal facilities. Suspected cases should be reported to public health authorities.
• Salmonella are killed by stomach acid. People taking antacids or with weakened immune systems need fewer organisms to become infected. 
• Foods that may contain Salmonella, such as raw meat, poultry and fish, should be stored separately from other foods, ideally at temperatures below 10 degrees Celsius.
• When preparing foods that could contain Salmonella, use a separate cutting board and utensils to avoid transferring pathogens.
• Poultry, fish and meat should be thoroughly cooked to kill Salmonella. Only heating above 70 degrees Celsius for at least ten minutes will inactivate the pathogens. This temperature must be reached inside the food. Freezing does not kill the bacteria. Minced meat should not be stored for more than one day and dishes containing raw egg should be consumed quickly. When thawing meat, it is advisable to discard the thawing water immediately.
• After shopping, foods high in protein and water content, such as raw meat, salads and seafood, should be put straight into the fridge to prevent Salmonella growth.
• All utensils and work surfaces that have been in contact with raw meat or poultry should be thoroughly cleaned and disinfected.
• Hands should be washed regularly and thoroughly with water and soap, especially after using the toilet, before preparing food and after contact with animals.
• Kitchen towels and cloths should be changed regularly and washed at at least 60 degrees Celsius to prevent spread of Salmonella.
• Reptiles such as turtles should not be kept as pets, particularly in households with children under two years, as they often carry Salmonella and can increase infection risk.
• With severe diarrhoea and vomiting, drink plenty of fluids, ideally electrolyte solutions. These help to replace lost water and salts. They can be prepared at home by mixing one litre of still drinking water with a level teaspoon of salt and 7 to 8 teaspoons of glucose or household sugar.
• Rest and a bland diet are important to give the digestive system time to recover, especially as symptoms ease.
• If symptoms of Salmonella food poisoning persist, particularly in babies, young children, pregnant women or older people, consult a doctor.

Salmonella food poisoning can cause serious health problems, but with appropriate precautions and hygiene it can be avoided. The variety of tips and measures shows how important it is to handle food carefully and maintain good hygiene. By being aware of these risks and acting accordingly, we can help reduce Salmonella infections and protect our health.