How does salmonella spread among people

Salmonella: what is it? - Distribution & importance

Salmonella are rod-shaped bacteria of the genus Salmonellanamed after their discoverer, the American bacteriologist Daniel E. Salmon (1850-1914). The approximately 2,500 different salmonellae, which were previously referred to as separate species, are now divided into serovars, i.e. into serologically different types. There are only two different types: Salmonella (S.) enterica and S. bongori, with almost all of the over 500 different serovars that can cause disease in humans, too S. enterica belong. The diseases predominantly affect the intestinal tract and are divided into enteric and typhoid salmonellosis.


Distribution & importance

Salmonella enteritis

Enteric salmonellosis are common worldwide. The main reservoir is animals, although these rarely develop symptoms. Farm animals such as cattle, pigs and poultry and animal foods produced therefrom are the most common causes of infection. The pathogens enter the body through consumption of contaminated food. The pathogens multiply rapidly under poor hygienic conditions, especially in various types of meat and poultry, eggs and raw milk. An infection can be detected by laboratory analysis through direct detection of the pathogen in a patient's stool.

Healthy people survive salmonella enteritis after a few days without special therapeutic measures if they drink enough fluids. Sometimes there are no complaints at all, although the pathogen can be detected in the body of the person affected. Primarily in small children, old people, pregnant women or patients with a weakened immune system, the infections can be severe and complex.

Of the approx. 500 serovars, only 20-30 are of permanent importance for foodborne diseases. The other serovars usually only appear regionally or for a limited time. The most important disease in Germany is salmonella enteritis or salmonellosis caused by serovars Enteritidis and Typhimuriumwhich often manifests itself as diarrhea with vomiting. The number of Salmonella diseases increases in the summer months and mainly affects the age groups under 10 and over 60 years of age. Men and women are roughly equally affected. Especially in the warmer seasons, the daily press regularly draws attention to the topic with reports on salmonella infections in old people's homes, canteens or kindergartens. Apart from spectacular outbreaks, Salmonella infections can also occur in individuals or in private households.

In Germany there is an obligation to report all infections detected in the laboratory. However, many cases are not recorded because laboratory diagnostics are often not initiated for the less severe diseases. The number of reported cases has been falling steadily since the mid-1990s. This can probably be traced back to targeted control strategies in livestock husbandry and the so-called "Egg Ordinance", with which the obligation to label eggs with regard to origin, husbandry and storage date was tightened. In 2017, the Robert Koch Institute received a total of 14,269 infections from Salmonella reported, ie 17 cases per 100,000 population, 45% of which were due to the serovar Enteritidis, 34% up Typhimurium. For comparison: the average between 2001 and 2004 was 82.1 diseases per 100,000 inhabitants. Salmonella are after Campylobacter- Pathogen the second most common pathogen causing bacterial gastrointestinal infections in Germany. Of the cases reported in 2017, Germany was the likely country of infection in 74%, the others were acquired in typical holiday countries (e.g. Turkey, Egypt, Thailand, Spain).

Typhoid and Paratyphoid

A distinction must be made between typhus abdominalis and paratyphus, which are only caused by very specific serovars: Salmonella Typhi (more accurate: Salmonella enterica, Serovar Typhi) or. Paratyphi A, B and C. They show a clinical picture that differs significantly from enteritis, which manifests itself as a generalized systemic, high-fever infection, in which the intestine but also other organs are often involved. Typhoid and paratyphoid fever are common all over the world, but are predominantly found in developing countries today.