What is salmonella?

On March 8, 2022, the Belgian Food Safety Authority (AFSCA) decided to stop production at the Arlon factory that produces Kinder chocolates, suspected of being the source of the salmonellosis epidemic that has hit several European countries. In fact, Italian manufacturer Ferrero has recalled the famous surprise gift eggs sold in France, Belgium, the UK, Ireland, Sweden and the Netherlands. On this occasion Science and the future Deciphers what salmonella is and what diseases are caused by these bacteria.

Salmonella, bacteria of the gastrointestinal tract of animals and humans

Salmonella (scientific name of the genus: salmonella) belong to the family Enterobacteriaceae. Their name comes from the Greek. entero, which means “gut” because they colonize the digestive tract of most warm-blooded and cold-blooded animals. In addition to humans, their natural reservoir is animals, both wild and domestic. Thus, poultry, pigs, cattle, sheep, goats, as well as dogs, cats and new pets (eg reptiles such as snakes, iguanas, tortoises or sea turtles) are often asymptomatic carriers of these bacteria. These microorganisms are also present in faeces and can survive for several weeks in a dry environment and several months in water.

Bacterial genus, two species and two types of salmonellosis

There are two types of Salmonella (Salmonella enterica and Salmonella bongori), are then classified according to their serotypes, i.e. their reaction in the presence of serum containing antibodies. More than 2600 serotypes (or serovars) have been identified. Three serotypes account for 61% in France in 2018 salmonella discovered.

Most serotypes Enteritidis (from poultry) followed by serotype variant Tifimurium probably spread by pig breeding; third place serotype Tifimurium. These three strains are the cause of non-typhoid salmonellosis, which causes more or less severe gastroenteritis. This salmonellosis is the second leading cause of foodborne illness in Europe. Much less often in France, two serotypes are observed (salmonella typhoid fever and Salmonella paratyphi) are respectively responsible for typhoid fever and paratyphoid fever, also called typhoid salmonellosis.

How do you get infected with salmonellosis? And with what products?

In France, 92% of the annual cases of salmonellosis are associated with food transfer when eating contaminated raw or undercooked animal products (eggs, meat, milk, cheese) or when eating fresh fruit or raw vegetables contaminated with animal feces. For example, in 2018, the revealed data show that eggs and products made from raw or undercooked eggs (chocolate mousse, tiramisu, mayonnaise, etc.) were most affected. However, many products avoid investigation.

Click on the table below to see it in a larger size:

Number of collective food poisonings (TIAC) ​​by type of food (confirmed or suspected) – France, 2018 Source: French Public Health / Epidemiological data / Surveillance of collective food poisonings. Mandatory declaration data, 2018 / January 2019

Salmonella outbreaks have also been associated with the consumption of food products such as powdered milk or chocolate. These epidemics are most often attributed to the lack of hygiene seen in the manufacturing plant or the use of a contaminated animal product. In the origin of human salmonellosis cases, we also find contact with animals, either directly by touch or through the environment. People themselves can transmit the disease, even if they are healthy carriers, if they do not follow certain basic hygiene practices, such as washing their hands after going to the toilet and before preparing food. This explains the number of epidemics observed in reception structures (kindergartens) and collective catering.

Click on the map below to see it in a larger size:

Number of collective food poisonings (TIAC) ​​by suspected or confirmed pathogen between 2006 and 2018. salmonella represents an average of more than 150 collective pollution per year. Source: French Public Health / Epidemiological data / Collective food poisoning surveillance. Mandatory declaration data, 2018 / January 2019

What are the symptoms of salmonellosis? What are the possible treatments?

Salmonella infections are manifested by gastroenteritis. The most common symptoms are fever, diarrhea, headache, chills, vomiting, and abdominal pain. Most often they appear between 12 and 36 hours after infection and disappear at the latest after a week. On the other hand, the patient may remain contagious for several weeks after recovery. infection salmonella in debilitated people (infants, small children, pregnant women, the elderly or people with a weakened immune system) can be complicated: diarrhea can persist for several days and lead to severe dehydration. In addition, generalized infections (sepsis) may occur. In very severe cases, antibiotics are prescribed, often as recommended by the National Reference Center (CNR). Its experts are coordinating an antibiotic strategy to avoid the emergence of new resistant strains. On average, 22% of reported cases require hospitalization, and in 0.8% of cases, the outcome is fatal. Although major salmonellosis outbreaks regularly make headlines, 60-80% of cases are classified as isolated cases or go undiagnosed.

What prophylaxis can be put?

The first prevention is the strict application of hygiene and control measures at all stages of the food chain, from production to food preparation, both in industrial premises and in the home. For individuals, French Public Health has issued a 10-point hygiene recommendation. In France, salmonellosis of the same foodborne origin must be automatically declared, and this at the occurrence of a second case under the obligation established in 1987 for all collective foodborne diseases (Tiac). CNR evaluates 8,000 to 10,000 strains each year salmonella from laboratories of biomedical analyzes and laboratories of hospital centers. Participates in epidemiological studies, types strains and controls their resistance to antibiotics. This last issue has been a public health concern since the emergence of resistant strains. Monitoring is also carried out at the European level by the European Food Safety Authority and the European Center for Disease Prevention and Control, as a contaminated product may be sold or manufactured outside of our borders. However, some NGOs regret that more restrictive measures were not taken to force the agri-food industry to act more rigorously and condemn the lack of control over food production chains. As a result, professionals are both judges and parties…

Investigators from the research department of the Gendarmerie of Angers during a search of the headquarters of Lactalis as part of an investigation into the presence of salmonella in the milk of babies of this industrial dairy farm (Laval, France, January 17, 2018).© JEAN-FRANCOIS MONIER / AFP

What are the risks of contracting typhoid fever in France?

In France each year, 83% of the 100-250 reported cases of salmonellosis typhoid (or typhoid and paratyphoid) are in patients who have traveled to Africa or Asia. One exception: the territories of Mayotte and Guyana, where epidemics are frequent. In France, the Pasteur Institute identified two small local epidemics (7 to 10 cases) in Paris in 2003 and 2006. This form of salmonellosis is also subject to registration.

On the other hand, according to WHO, typhoid fever affects between 11 and 21 million people worldwide and causes between 128,000 and 161,000 deaths. Paratyphoid is responsible for 6 million cases and 54,000 deaths each year. These fevers occur mainly in countries without access to drinking water and effective sanitation. Children and vulnerable people are the first victims. Indeed, the transmission of bacteria is different from the transmission of non-typhoid salmonellosis. Infection occurs through the feces of sick or healthy carriers. Salmonella typhi Where Paratyphoid. People most often become infected by drinking water or food that is eaten raw and contaminated with faeces (sewerage, divorce, etc.). There is a typhoid vaccine that provides 50 to 65% protection. This vaccine is not protective against paratyphoid.

Typhoid or non-typhoid salmonellosis remains a public health problem worldwide.

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