Salmonellosis: what it is, how it is contracted, and how it manifests

In 2008–2009 in the United States, a salmonellosis outbreak linked to King Nut creamy peanut butter affected 714 people, nine of whom died. A seemingly harmless jar of the product turned out to be a source of severe intestinal infection — and reminded us that the microbe does not ask permission. Salmonellosis remains one of the most common foodborne infections, and the discussion of it is best started with the structure of the causative agent itself.

What salmonellosis and Salmonella are

Salmonella is a group of bacteria of the genus Salmonella in the family Enterobacteriaceae; they are named as one of the common causes of food poisoning. Salmonellosis is an acute intestinal infection of animals and humans caused by these bacteria; the disease is classified as an anthropozoonosis and is characterized primarily by intoxication and damage to the gastrointestinal tract. Once in the small intestine, salmonellae colonize its wall and release exotoxins, which cause loss of water through the intestine, impair vascular tone, and damage the nervous system. The scale of the problem is visible in the statistics: in the EU zoonoses report for 2022, salmonellosis was named the second most frequent foodborne gastrointestinal disease in humans — 65,208 confirmed cases, or 15.3 per 100,000 population.

How infection occurs: sources and routes of transmission

The source of infection can be animals and humans, but the main role in epidemiology belongs to animals. The mechanism of transmission is fecal-oral, the main route is foodborne, mainly through products of animal origin contaminated with salmonellae. The bacteria are found in raw poultry, eggs, and beef, sometimes on unwashed fruits and vegetables; in birds, salmonellae are found in eggs, meat, and internal organs. Infection is also possible after contact with domestic animals, especially reptiles — snakes, turtles, and lizards; pigs, cattle, and house rodents are also significant. The incubation period ranges from 6 hours to 3 days, averaging 12–24 hours, and the first symptoms of foodborne infection appear several hours or days after eating, sometimes weeks later.

How salmonellosis manifests

The full-blown form of the disease consists of intoxication and intestinal manifestations.

• rise in body temperature, general weakness, headache;
• nausea and vomiting, loss of appetite;
• abdominal pain and repeated loose watery stools.

Usually such symptoms last 4–7 days. In severe cases, dehydration develops, the liver and spleen enlarge, renal failure is possible, and in rare cases death occurs. An abortive form also occurs: the person does not suffer themselves but remains a bacterial carrier and serves as a source of infection for others.

How salmonellosis is diagnosed

Diagnosis is built comprehensively: epidemiological data, symptoms, and the results of laboratory tests aimed at isolating and typing the causative agent are taken into account. The main laboratory step is stool testing, in which bacteria are isolated from the sample. For typing salmonellae, the indirect, or passive, hemagglutination test is used — IHA (PHA). The purpose of typing is practical: in Europe in 2022, 67.3% of cases were due to S. Enteritidis and 13.1% to S. Typhimurium.

Why salmonellosis is dangerous and who is at risk

Most people recover without specific treatment, but in older adults, infants, and people with chronic health problems, the course can be more severe. The penetration of Salmonella into the bloodstream makes the disease serious; according to the European report for 2022, the proportion of hospitalized cases reached 38.9% with a case fatality rate of 0.22%. Carriage also adds complications: salmonellosis often becomes chronic, and the carrier does not feel symptoms while being able to infect others.

When to see a doctor

You should see a doctor if diarrhea is prolonged, blood appears in the stool, and in a child or older adult there are signs of dehydration — infrequent urination, dark urine with a strong odor. There are conditions in which time is counted not in days but in minutes.

Salmonellosis itself is not a reason to call an ambulance; 103 and 112 — if the patient has vomiting of blood or vomit the color of coffee grounds, green vomiting, a stiff neck with pain when looking at bright light, sudden severe headache, sudden severe abdominal pain, bluish, gray, pale, or mottled skin and lips, severe difficulty breathing, confusion.

This review is for reference: it explains how Salmonella is structured and how it manifests, but does not replace consultation with a doctor who sees a specific person, not average figures.

This content is for reference and does not replace a doctor's consultation. Medical disclaimer