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Salmonella – causes, symptoms, methods of diagnosis, treatment and prevention tips

Salmonella is a type of bacteria that causes a disease that affects the digestive system, and this disease is widespread in industrialized countries and is known as salmonella disease.


This disease is transmitted to humans through eating food contaminated with bacteria, especially eggs and dairy products, which are contaminated during the process of their production, storage or distribution. It can also be caused by eating contaminated meat or drinking contaminated water.

The severity of salmonella symptoms varies according to each case, and they range from simple disorders of the digestive system (abdominal cramps, vomiting and diarrhea) with high temperatures. The disease can progress and produce more severe symptoms, including general debility and other illnesses.

What is salmonella bacteria?

Salmonella is one of the most common types of bacteria that cause diseases in humans, and it is transmitted to humans and infects the digestive system through contaminated food and causes salmonella disease.

Salmonella bacteria live naturally in the intestines of animals such as birds and mammals.

The difference between poisoning caused by toxic substances and poisoning caused by microorganisms?

Poisoning occurs in the body as a result of eating food containing toxic substances. If the cause of poisoning is caused by the presence of microorganisms such as germs and viruses, this condition is called microorganism poisoning.

If the poisoning is due to toxins present in food it is called food poisoning.

Enteroviruses and Salmonella bacteria are the most poisonous microorganisms in humans.

Characteristics of salmonella bacteria

Salmonella is a group of Gram-negative bacteria that belong to the family of intestinal bacteria. These bacteria are microorganisms that can live in the intestines of reptiles, birds and mammals, including humans.

Salmonella bacteria are stubborn and able to move thanks to the presence of flagella, these bacteria can reproduce and live well at room temperature and inside the human body, but they cannot tolerate temperatures or high pH.

Salmonella bacteria are sensitive to physical and chemical factors, for example, in cold temperatures (5 degrees Celsius or less) the reproduction of these bacteria stops, but they do not die, but they freeze and their growth also stops.

Cooking food helps greatly reduce the possibility of infection as the heat kills bacteria instantly.

There are about 200 types of salmonella bacteria, of which 50 are dangerous to humans, and the most dangerous types are from an animal source.

What is salmonella typhi and non-typhoid?

As we said above, there are many types of bacteria of the genus Salmonella that infect humans and cause diseases, and in general the salmonella infection that affects humans can be divided into two types, which are Salmonella typhi and Salmonella non-typhi.

Both types cause very serious health conditions and are especially common in developing countries.

The non-typhoid salmonella is called the salmonella minor, and it is the most common type, the symptoms of infection with this bacterium are limited to the digestive system only, and it can infect types of animals, including animals raised for food, which increases the risk of transmission to humans.

Note: In our article, we will focus more on salmonella infection that is not typhi or salmonella minor, as it is the most common and common type.

Causes of salmonella infection

The ideal place where salmonella bacteria live and breed and breed in are wild animals, pets or farm animals such as chickens, pigs, livestock, rodents, dogs and cats.

These bacteria are excreted from the bodies of animals through faeces, and if food or water is contaminated with these bacteria, they can be transmitted to humans.

For this, salmonella can be considered a disease of animal origin, that is, it is an infection transmitted from animals to humans.

Contaminated food is the main source of salmonella infection in humans.

Food contaminated with salmonella bacteria can be exposed due to the following reasons:

  • Food may be taken from an infected animal including meat, eggs and milk, which is not adequately heat treated.
  • Contamination of food or water with feces of infected animals or humans.

Foods that cause a risk of spreading salmonella bacteria to humans are:

  • Raw or undercooked eggs, or any foods that contain raw eggs, such as cream or sauces.
  • Meat, especially raw or undercooked poultry
  • Crustaceans, mollusks and fish
  • Unpasteurized milk or dairy products
  • Unclean fruits and vegetables (watermelon – melon – tomatoes – lettuce and others)
  • Sweets, creams and ice creams.

Important note

Food contaminated with salmonella bacteria does not show any difference from clean foods and does not show any changes in color, smell, taste or texture.

Salmonella spread in the world

On the European continent, about 90 thousand European citizens become infected with salmonella every year, and it seems that the number of people infected with this disease is increasing in most industrialized countries. This can be explained by several factors such as:

  • Strains of bacteria emerge that are resistant to antibiotics
  • Import of meat and animal products
  • The spread of agriculture on a large scale and its access to places to raise animals
  • Eat ready-to-eat foods in restaurants that could be unclean

This should follow some preventive rules in order to ensure that you do not catch this disease.

How is the pathogen transmitted to humans?

Salmonella bacteria live in the gastrointestinal tract of many types of animals, and these bacteria are naturally inside the animal without causing any disease or showing any symptoms.

There are three ways to transmit salmonella infection to humans: contaminated food, contaminated water, and pets.

When food, water, or pets come into contact with the feces of an infected animal, they become contaminated with bacteria that can be transmitted to humans.

The most common causes of salmonella transmission are:

  • Incomplete cooking of food
  • Lack of attention to hygiene in places where food is prepared
  • Leave raw foods and cooked foods together
  • Leave meat and vegetables together
  • Use the same tools for raw or cooked foods

Food contaminated with salmonella bacteria does not have any abnormal smell, flavor or shape, and therefore it does not raise suspicion and this increases the possibility of transmission.

Transmission of infection by direct contact

Salmonella can be transmitted by contact with infected faeces from any animal that has these bacteria in the digestive system. Animals that cause transmission are in most cases pets such as cats, dogs, birds, water turtles, and others:

Factors that increase the risk of developing salmonella disease

  • Eat raw or undercooked seafood
  • Not washing hands after handling food, animals, or faeces
  • Drinking unpasteurized milk
  • Not storing food properly, for example, storing eggs at room temperature
  • Gastrectomy or drug therapy that reduces stomach acid
  • Infections and immune intestinal tumors
  • Have recently taken antibiotics
  • Living in crowded places

Symptoms of salmonella disease

Salmonella has a group of symptoms, the severity and severity of which can vary according to each case.

The severity of these symptoms varies according to the patient’s health condition, the type of strain that caused the disease, its number, the extent of its resistance to drug treatment, and the strength of the immune system.


The low level of stomach acidity provides an environment that helps pathogens spread, which leads to diarrhea. Diarrhea is a reaction or defense mechanism by the body to get rid of pathogens. the body.

Healthy people are more able to resist the disease, especially when the infection is transmitted orally, and if the amount of contaminated food that these people eat is small, this leads to only mild symptoms.

But in other cases, that is, when a person eats large quantities of food contaminated with Salmonella bacteria, the symptoms can be severe and lead to the weakness of the disease and general debility.

Mild salmonella infection has symptoms limited to the digestive system, and causes gastroenteritis. Only in more severe cases, it causes septicemia with symptoms outside the intestine (arthritis – osteomyelitis – pneumonia – meningitis – endocarditis … … etc.).

Salmonella usually causes:

  • nausea.
  • stomach ache
  • Diarrhea with liquid stools mixed with mucus and sometimes small amounts of blood (bloody stools).

Symptoms such as:

  • Green stools
  • Fever (38 – 39 ° C)
  • vomiting
  • Arthritis
  • a headache

When do salmonella symptoms appear?

Typically, salmonella symptoms appear about 12-72 hours after eating contaminated food or exposure to the bacteria. This short period is called the incubation period, during which the salmonella multiplies in the intestine.

Serious salmonella infection

Children and the elderly may have asthenia, a more severe clinical picture, and symptoms outside the intestine, such as:

  • Pneumonia
  • Endocarditis
  • Pyelitis
  • nephritis

If salmonella is able to reach the bloodstream, it can cause blood poisoning or infections affecting the bones and meninges.

The potential consequences of these dangerous types of salmonella include:

  • Meningitis (inflammation of the membranes lining the brain and spinal cord)
  • Osteomyelitis (bone infection)
  • Septic arthritis

The mortality rate from salmonella disease is very low. Newborns, infants, the elderly and those who are debilitated by other illnesses such as AIDS patients are most at risk.

How long do salmonella symptoms last?

The severity of the above symptoms varies, but usually resolves within 4-7 days. Severe forms of the disease can affect vulnerable people such as infants, the elderly, and those with weakened immune systems that require hospitalization.

The diagnosis

The diagnosis of Salmonella is confirmed by a stool culture and analysis. The analysis allows to highlight the presence and identification of the salmonella serotype that caused the infection.

In severe forms, the disease may be detected by culture of blood, urine, or excretions.


Since it is a bacterial infection, it is normal for salmonella to be treated with antibiotics. In fact, the disease is often treated without antibiotics, since most cases are in the form of mild gastroenteritis, so the symptoms automatically improve within a few days.

Also, the treatment procedure includes drinking plenty of fluids, to replace water and minerals lost due to vomiting and diarrhea.

It is also common to give lactic and probiotics. They are also very useful for restoring beneficial bacterial species that are found in the intestine and which die from the use of antibiotics.

Treatment with antibiotics is only limited to the elderly or immunocompromised and children under the age of two, and in severe infections that cause additional intestinal symptoms.

In contrast to these cases, antibiotic therapy leads to drug resistance.


Salmonella infection can be avoided with some simple hygiene measures. These procedures include raw foods, especially those of animal origin, which include:

  • Food cooling
  • Frequent washing of hands and surfaces such as cutting boards and dishes
  • Separate raw meat from other foods
  • Cook food at high temperature

To reduce the risk of contracting salmonella, it is recommended to wash your hands before, during and after preparing food.

Foods of animal origin should be cooked, especially poultry meat and eggs, this reduces the risk of infection, as the bacteria die with heat. However, it must be remembered that salmonella can contaminate tables, stoves, cutlery, and dishes, and thus spread from one food to another during the preparation stages. For this reason, the sterilization effect is nullified by the cooking heat if, for example, the knife used for cutting raw meat is used shortly afterwards to chop cooked meat or raw vegetables ready to eat. For this reason, and to avoid cross-contamination with bacteria, raw foods should be separated from cooked foods.

The temperature that causes salmonella to kill

In order for all bacteria that may be present to die, it is possible to cook all parts of the food at 70 ° C for at least a quarter of an hour.

Note: If the toxins of the bacteria have already been formed, the heat does not render the toxin unaffordable. For this, only buy fresh foods.

Some practical tips to avoid getting infected with salmonella

Always wash your hands with soap and water

  • Before starting to cook
  • before eating
  • Before and after eating raw foods
  • After handling garbage
  • Before cleaning surfaces
  • After touching pets and cleaning their cages or homes

Don’t eat raw meat and undercooked eggs. Also, pay attention to foods that contain raw egg creams or sauces (mayonnaise – eggnog … etc.).

Use gloves if you have cuts or injuries on your hands.

Do not eat raw eggs.

Always ensure that your drinks are not exposed to the sun or other heat sources.

Regularly check food storage conditions in the refrigerator and keep eggs and all fresh foods (mayonnaise, creams, sauces) at 4 ° C or below, preferably fresh without storing them for a long time.

Avoid cross-contamination between foods by separating raw meat from cooked and carefully washing all utensils used for preparing and cutting raw food. Protect foods and place them in airtight containers to avoid contamination.

Before eating, wash fruits and vegetables. To eliminate microbes and toxic materials such as pesticides, wash them before putting them in the fridge as the increased humidity helps mold and bacteria grow.

Clean the fridge often with a clean, sterile sponge dampened with a little vinegar or some detergent.

Salmonella and eggs

To reduce the risk of contracting salmonella from eggs, in addition to the prevention measures mentioned above, you should pay attention to: 

  • When the shell is broken, try not to crush it, to avoid small pieces of the shell getting into the yolk or egg whites.
  • Get rid of the remnants of eggs in the trash, and avoid put on work surfaces or contact with kitchen tools.
  • After breaking the bite, wash your hands with soap and water.


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