What is salmonellosis?
Salmonellosis is a disease that occurs due to an infection by gram negative enterobacteriaceae of the genus Salmonella. In fact, most Salmonella exist in the gut of vertebrate animals and are most often transmitted to humans through contaminated food. In human pathology, salmonellosis includes two main types of disease:
- Typhoid and paratyphoid fevers
In elderly people, infants, pregnant women or immunosuppressed people, the infection can be even deadly.
Salmonellosis remains the second leading cause of gastrointestinal infection in humans after campylobacteriosis, and an important cause of foodborne infection in Europe with 91,857 confirmed cases in 2018.
Indeed, The National Reference Center for Escherichia coli, Shigella and Salmonella (CNR), located in the Enteric Pathogenic Bacteria Research and Expertise Unit at the Institut Pasteur, is in charge of the microbiological monitoring of human salmonellosis. Each year, the CNR assesses 8,000 to 10,000 strains of Salmonella from medical biology analysis laboratories and hospital center laboratories.
How do you get salmonella infection?
Given the wide spectrum of animals that can carry Salmonella, a wide variety of food products, eaten raw, undercooked or that have been contaminated post-cooking, can be the source of contamination. These includes meat products, cold cuts, eggs or raw milk, and some cheeses.
More rarely, contamination can originate from direct contact with a sick animal or a healthy carrier through the hands. In this regard, the vast majority of reptiles are healthy carriers of Salmonella, these new pets are the cause of severe infections in infants.
Finally, the contamination of foods of plant origin, if they are not well washed or cooked before consumption, can also be the source of a Salmonella infection. To illustrate, the fruits or vegetables may come from a field where there's water contamination. Furthermore, this may result from using the same knife you used for meat and poultry on salads or other uncooked foods.
Symptoms of salmonella infection:
Infections by Salmonella most often manifests in the form of gastroenteritis (stomach flu). The incubation period is usually 1 to 2 days and depends on the dose of bacteria, the health of the host and the characteristics of the Salmonella strain. Fever, headache, diarrhea, nausea, vomiting and abdominal pain are the main symptoms of the infection.
Salmonella infections can also manifest as typhoid and paratyphoid fever. The symptoms vary from stomach ache, diarrhea or costipation, cough, weakness and headache.
In general, Salmonella symptoms usually lasts up to 2-7 weeks, although diarrhea can last up to 10 days. On the other hand, it may take months until the bowel movement returns to its normal state.
Pets: Owning a pet including reptiles and birds increase your risk upon contact.
Poor sanitation: Living or traveling to an area with poor sanitation increases your risk of typhoid fever.
Low stomach acidity: Taking antacids lowers stomach acidity which is one of the methods to fight off Salmonella.
Antibiotics: Taking antibiotics lowers the good bacteria level in your intestines making it easier for Salmonella to live.
Health problems: Diseases that lowers your immunity puts you at a high risk to acquiring Salmonella. For instance, diseases that lowers immunity include AIDS, malaria, and sickle cell anemia. Moreover, taking cortocosteroids and immunosuppressants after transplant lowers immunity.
How to prevent salmonella infection?
The best protection against the risk of salmonellosis is thorough cooking of food, especially meat, at least 65°C for 5 to 6 minutes. For frozen or deep-frozen ground beef, cooking should be done without first thawing as it increases the risk of bacterial multiplication. Besides, the cold blocks cease the development of bacteria but does not kill them.
At the end of the 1980s, the number of infections linked to the Enteritidis serotype had increased sharply in Europe following the contamination of laying hen farms by this serotype. The bacteria of this serotype has the particularity of being present not only on the surface of the egg shell, but also in the very contents of the intact eggs. For this reason, it was necessary to store eggs in the refrigerator, to keep egg-based preparations without cooking (mayonnaise, creams, pastries, etc.) cold and to consume them as close as possible to their manufacture. In addition, the most vulnerable people (elderly, sick, infants, pregnant women) should avoid the consumption of raw or undercooked eggs.
Finally, it is advisable to wash your hands after contact with a live animal (especially reptiles) or even to avoid contact with pet reptiles for all vulnerable people such as infants, the immunosuppressed people and pregnant women.
- Culture: It's possible to rule out a Salmonella infection by a urine and stool when there's diarrhea or bloody stool. However, a culture of cerebrospinal fluid, blood and bone marrow is important to diagnose Salmonella infection upon having enteric fever.
- PCR: Polymerase chain reaction is one of the new diagnostic tools in clinical settings which is more prevalent in research laboratories.
Salmonella infection treatment:
Without doubt, in adults of normal physical condition, gastroenteritis disappears without treatment after 3 to 5 days on average. On the other hand, antibiotic therapy can be prescribed in the elderly, infants, or immunocompromised people in whom the infection can be more severe, even fatal.
Complications of salmonella infection:
Certainly, it's rare for salmonella infections to become life-threatening. Meanwhile, complications can develop in some patients, especially infants, elderly, pregnant women, and people with weak immune system. Such life-threatening complications are:
- Dehydration: Losing excessive water from diarrhea and vomiting can lead to dry mouth, less tear production and urination, and sunken eyes.
- Typhoid complications: These manifests as neurological complications including psychosis, acute cerebellar ataxia, delirium and Guillain-Barré syndrome. Also, inappropriate treatment or the unresponsiveness may lead to chronicity.
- Gastrointestinal complications: These include having bloody stool "hemorrhage" and perforation.
-Ajmera A, Shabbir N. Salmonella. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK555892/#_NBK555892_pubdet_
-Bhandari J, Thada PK, DeVos E. Typhoid Fever. [Updated 2021 Oct 26]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK557513/#_NBK557513_pubdet_
-Sattar SBA, Singh S. Bacterial Gastroenteritis. [Updated 2021 Aug 11]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. https://www.ncbi.nlm.nih.gov/books/NBK513295/#_NBK513295_pubdet_
-Nair S, Patel V, Hickey T, et al. Real-Time PCR Assay for Differentiation of Typhoidal and Nontyphoidal Salmonella. J Clin Microbiol. 2019;57(8):e00167-19. Published 2019 Jul 26. doi:10.1128/JCM.00167-19
-Image credits: https://www.freepik.com/vectors/meat-illustration