Salmonella

Salmonella
Secondary electron microscope image of Salmonella (colored red)
Systematics
Domain : Bacteria (bacteria) Trunk : Proteobacteria Class : Gammaproteobacteria Order : Enterobacterales Family : Enterobacteriaceae Genre : Salmonella
Scientific name
Salmonella
Lignières 1900
species
According to the currently valid nomenclature there are only two species : Salmonella enterica Salmonella bongori Salmonella enterica is divided into the six subspecies listed below . Within the subspecies, individual isolates are assigned to one of the more than 2500 serovars .

Salmonella ( Salmonella ) are a genus of rod-shaped bacteria from the family of Enterobacteriaceae (Enterobacteriaceae), which can cause illness in humans and many animals. Joseph Lignières named the genus he described in 1900 after the American veterinarian Daniel Elmer Salmon .

description

Salmonella are rod-shaped Gram - negative bacteria with a diameter between about 0.7 to 1.5 µm and a length of about 2 to 5 µm. They are predominantly actively mobile, peritrich flagellated , facultatively anaerobic , chemoorganotrophic with oxidative and fermentative energy metabolism and not spore-forming . They are summarized in the genus Salmonella and assigned to the Enterobacteriaceae family . They are closely related to the genus Escherichia . They occur all over the world in animals of varying temperature and of the same temperature , in humans and in habitats outside of living beings.

Salmonella as a pathogen

Salmonellosis (diseases caused by Salmonella) belong to the category of zoonoses , since humans can be infected by animals as well as animals by humans. Infection through food is also common. Salmonella are particularly common on eggs and poultry meat. In contrast to the past, pork is now rarely contaminated with salmonella.

A distinction is made between enteritis and typhoid / paratyphoid salmonella, the latter causing more severe diseases due to special virulence factors and a capsule protein (virulence antigen) (e.g. Salmonella enterica subsp. Enterica serovar typhi, Salmonella typhi for short ). Salmonella Typhi is not found in animals and is adapted to humans.

Enteritis salmonella, for example Salmonella enterica subsp. enterica Serovar Enteritidis (abbreviation Salmonella Enteritidis) and Salmonella Typhimurium cause diarrheal diseases that usually heal spontaneously in humans and usually do not require antibiotic treatment. However, serious illnesses (general infections) can be caused in risk groups such as infants, young children, the elderly, HIV patients and immunocompromised patients.

In Germany , salmonellosis belong to the so-called reportable diseases (Section 6 and Section 7) of the Infection Protection Act . Official reports have fallen from around 200,000 in 1990 to around 55,000 in 2005. In 2014, only 16,220 cases were reported in Germany. 17 cases were reported as dead due to illness. It is estimated that every fifth person in Germany carries salmonella. In Switzerland, laboratories report between 1200 and 1500 evidence of salmonella annually. Salmonella can live for weeks outside the human or animal body. Sunlight ( UV radiation ) accelerates the death of the pathogens. They can be detected in dried feces for over 2.5 years. To avoid Salmonella infections, it is recommended that the food be heated to 75 ° C (temperature in the core) for at least ten minutes. At only 55 ° C, it takes an hour for potential salmonella contamination to be sufficiently reduced. Freezing does not kill the bacteria. In acidic media, the salmonella die quickly; common disinfectants kill them within a few minutes. At temperatures below 6 ° C, reproduction is significantly slowed.

history

• In 1874, the Polish pathologist Tadeusz Browicz first described a bacterium as the cause of typhus .
• In 1880 the causative agent of typhus abdominalis was discovered in humans by Karl Joseph Eberth and Robert Koch .
• In 1881 Georg Gaffky succeeded in breeding the pathogen in pure culture (published in 1884).
• 1888 August Gärtner discovers the cause of the "meat poisoning" and thus a causative agent of Salmonella enteritis ( Bacillus enteritidis Gärtner = Salmonella enteritidis ).
• In 1889 Daniel Elmer Salmon , after whom the genus Salmonella was named, found the "pig cholera" bacteria.
• In 1892 Friedrich Loeffler discovered the enteritis pathogen Salmonella typhimurium .

Systematics and nomenclature

A Salmonella culture on deoxycholate citrate agar (DC agar)

Salmonella spp. on XLD agar

Macro shot of the colony morphology on XLD agar:
Na ₂ S ₂ O ₃ is metabolized to H ₂ S , which reacts with iron (III) ions in the nutrient medium to form black iron sulfide

The systematics and nomenclature of the Salmonella species is very complex. In the initial phase, Salmonella species were formed and named according to clinical criteria, for example Salmonella typhi-murium (mouse typhus), S. abortus-ovis ( abortion of the sheep), S. cholerae-suis ( cholera of the pig).

In 1941, Kauffmann defined every newly discovered serovar as a new species on the basis of serological findings .

When it was recognized that the host specificity of some species did not exist - S. typhimurium and S. choleraesuis are also pathogenic for humans - new serovars were regarded as independent Salmonella species and named after the location where the first strain of the new species was isolated has been.

In 1966, at the Ninth International Microbiological Congress in Moscow, it was decided to remove the hyphen in the species name (e.g. S. typhimurium ).

On the basis of molecular biological findings (in particular DNA / DNA hybridization ), Le Minor and Popoff proposed that the genus Salmonella should be viewed as consisting of only one species, namely S. enterica . This should be divided into serovars, from which six groups are formed, which are regarded as subspecies (abbreviated to ssp.). 99.5% of salmonellae isolated from people with salmonellosis and warm-blooded animals belong to group I. Representatives of the subspecies salamae (group II) and houtenae (group IV) were isolated from reptiles; the least common are subspecies of group VI (subspecies indica ). S. enterica ssp. bongori was classified as Group V by Le Minor and Popoff (1987), but Reeves et al. a. (1989) suggested group V as a separate species S. bongori. to call. Each subspecies in turn contains numerical serovar names.

Medically relevant salmonella belong to the

• Group I ( S. enterica ssp. Enterica ) and the
• Group IIIa ( S. enterica ssp. Arizonae ) and the
• Group IIIb ( S. enterica ssp. Diarizonae ).

These six salmonella groups can be classified using biochemical tests as follows:

Group (by subspecies)	Group (by number)	Malonate	ONPG	Dulcit	Salicin	Galacturonic acid	gelatin
S. enterica ssp. enterica	I.	negative	negative	positive	negative	negative	negative
S. enterica ssp. salamae	II	positive	negative	positive	negative	positive	positive
S. enterica ssp. arizonae , and S. enterica ssp. diarizonae	III	positive	positive	negative	negative	weak	positive
S. enterica ssp. houtenae	IV	negative	negative	negative	positive	positive	positive
S. enterica ssp. indica	VI	negative	variable	variable	negative	positive	positive
S. bongori	V	negative	positive	positive	negative	positive	negative

Explanations: Malonate: utilization of malonate as an energy and carbon source (C source); ONPG: hydrolysis of ONPG ; Dulcit: utilization of dulcit , a sugar alcohol , as an energy and carbon source; Salicin: Utilization of salicin , a glycoside that occurs in willow (generic name: Salix ), as a source of energy and carbon, Galacturonic acid: Utilization of galacturonic acid , the main component of pectins , Gelatin: hydrolysis of gelatin .

After almost twenty years of discussion, the proposals of Léon Le Minor and Michel Y. Popoff and Michael W. Reeves were adopted in 2005 . However, this formal system , created by microbiological systematists , is not in line with the traditional systematics of the Salmonella species and with the Kauffmann species name based on the serovars. However, microbiologists and infectiologists have been familiar with this naming principle for decades, so this incorrect naming is still widespread today.

According to the Kauffmann-White scheme, there are a total of more than 2500 Salmonella serovars, which differ on the basis of the occurrence of different O and H antigens . The O-antigens are part of the lipopolysaccharide (LPS) of the cell wall and the H antigens part of the protein components of the flagella ( flagella ), with which the salmonella can move. In addition, some species have an antigen in the mucous membrane ("capsule"), a so-called capsule antigen (= K antigen). Since only one H-phase can be detected with the Kauffmann-White scheme and both H-phases are definitely required for typing, the second (other) H-phase must be brought to training using a swarming plate according to Sven-Gard.

• O-antigen (= somatic antigen), localized in the outer membrane, lipopolysaccharide, thermostable, formaldehyde-not resistant , so-called surface antigens
• H-antigen (= flagellum antigen), thermolabile, formaldehyde-resistant .
• K antigen (= envelope antigen) consists of three fractions with different heat sensitivity and is assigned to the cell wall.

Epidemiological Groups

Classification of the serovars after adaptation to specific hosts:

• human-adapted serovars that cause typhoid or paratyphoid fever (e.g. Salmonella Typhi, Salmonella Paratyphi A, B and C),
• adapted to certain animal species serotypes that cause the animal related diseases and for other animal species and humans are not important Salmonella Dublin (cattle), Salmonella choleraesuis (pork), Salmonella Abortusovis, Abortusequi (sheep, horses) and
• Serovars without special host adaptation, which occur in all animal species as pathogens for enteritis and which cause food poisoning in humans .
• Serovars without special host adaptation, which occur in humans and animals as pathogens of salmonellosis and have a high virulence.

Possibilities of infection

Salmonella infections are possible:

• through uncleanliness in the food sector, especially in large kitchens
• through the excretions of sick, but also clinically healthy infected people (permanent excretors) and animals (endangered: nursing staff and other animals); especially by reptiles that are unrecognized and infected (infestation rate at 90%), a danger especially for small children
• from contaminated surface water and stale water (for example in shower hoses and water dispensers that have not been used for a long time)
• from unsanitary thawed poultry (many bacteria are in the thawed water) and
• through raw eggs from poultry infected with Salmonella (the salmonella are usually only on the eggshell, but can get inside if the cuticle is injured ).

Medically significant representatives

Salmonella Typhimurium under the electron microscope

• Salmonella enterica ssp. arizonae , in cold-blooded animals , poultry , mammals
• Salmonella Choleraesuis (Bacillus paratyphus B and C), intestinal commensal of pigs , pathogenic in the case of weak resistance ; People can become infected by eating the meat of sick pigs, which causes the pig's salmonellosis .
• Salmonella Enteritidis, found in the intestines of cattle , rodents , ducks (including their eggs) and humans; Pathogen causing calf paratyphoid fever and acute gastroenteritis in humans.
• Salmonella Paratyphi A, purely human pathogen , causative agent of "Paratyphus A" (Paratyphoid gastroenteritis), transmission through contact and infectious food or water.
• Salmonella Paratyphi B: There are two variants of this serovarietal that differ with regard to the fermentation of d-tartrate. The d-tartrate-negative variant occurs practically only in humans, is considered to be the causative agent of "Paratyphus B" and is rarely found in Central Europe. The d-tartrate-positive variant, on the other hand, is predominant in Central Europe. It has an animal reservoir, is considered to be the cause of salmonella enteritis and is also known as Salmonella Java.
• Salmonella Typhi, occurrence in temperate and subtropical zones, human pathogen causing typhus abdominalis, transmission through contact and infectious food, water or fly droppings. 3–5% of all sick people remain permanent eliminators .
• Salmonella Typhimurium , causative agent of a mostly fatal, febrile intestinal infection in birds and mammals, caused by contaminated feed . Trigger of salmonella enteritis (" food poisoning ") in humans.
• Salmonella Dublin, one of the pathogens causing notifiable bovine salmonellosis
• Salmonella Typhisuis, one of the causes of salmonellosis in pigs

Reporting requirement

In Germany, any direct evidence of Salmonella Paratyphi or Salmonella Typhi must be reported by name in accordance with Section 7 of the Infection Protection Act . In addition, the direct or indirect detection of other salmonella , if the evidence indicates an acute infection. The obligation to notify primarily concerns the management of laboratories ( § 8 IfSG).

In Switzerland, the positive and negative laboratory analytical findings on Salmonella ( Salmonella spp. ) Must be reported to laboratories in accordance with the Epidemics Act (EpG) in conjunction with the Epidemics Ordinance and Annex 3 of the Ordinance of the EDI on the reporting of observations of communicable diseases in humans .

literature

• Giulia Enders, Jill Enders (illustrations): Gut with charm. All about an underrated organ . Ullstein, Berlin 2014, ISBN 978-3-550-08041-8 .
• Werner Köhler : Salmonella. In: Werner E. Gerabek u. a. (Ed.): Encyclopedia of medical history. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , p. 1282.

Web links

Commons : Salmonella  - Collection of pictures, videos and audio files

• Significance of salmonella as a pathogen . Federal Institute for Risk Assessment

Individual evidence

1. ↑ Salmonellosis - RKI Guide for Doctors , online Robert Koch Institute , accessed November 21, 2016
2. ↑ Page no longer available , search in web archives: Salmonellosis - pathogen and transmission January 17, 2013, Swiss Confederation - Federal Office of Public Health (FOPH), accessed November 23, 2016
3. ↑ Werner Köhler : Infectious diseases. In: Werner E. Gerabek , Bernhard D. Haage, Gundolf Keil , Wolfgang Wegner (eds.): Enzyklopädie Medizingeschichte. De Gruyter, Berlin / New York 2005, ISBN 3-11-015714-4 , pp. 667-671; here: p. 670.
4. ↑ F. Kauffmann: The bacteriology of the Salmonella group . Munksgaard, Copenhagen, 1941.
5. ↑ ^{a b c} L. Le Minor, MY Popoff: Request for an opinion. Designation of Salmonella enterica. sp. nov., nom. rev., as the type and only species of the genus Salmonella. In: Int. J. Syst. Bacteriol. Volume 37, 1987, pp. 465-468.
6. ^ ^{A b} M. W. Reeves, GM Evins, AA Heiba, BD Plikaytis, JJ Farmer III: Clonal nature of Salmonella typhi and its genetic relatedness to other salmonellae as shown by multilocus enzyme electrophoresis and proposal of Salmonella bongori comb. nov. In: J. Clin. Microbiol. Volume 27, 1989, pp. 313-320. PMID 2915026 .
7. ↑ Referendmetodik för laboratoriediagnostik vid kliniskt mikrobiologiska laboratorier. ( Memento of May 27, 2006 in the Internet Archive ; PDF) Table 7
8. ^ Judicial Commission of the International Committee on Systematics of Prokaryotes: The type species of the genus Salmonella Lignieres 1900 is Salmonella enterica (ex Kauffmann and Edwards 1952) Le Minor and Popoff 1987, with the type strain LT2T, and conservation of the epithet enterica in Salmonella enterica over all earlier epithets that may be applied to this species. Opinion 80. In: Int. J. Syst. Evol. Microbiol. Volume 55, 2005, pp. 519-520. PMID 15653929
9. ^ BJ Tindall, PA Grimont, GM Garrity, JP Euzeby: Nomenclature and taxonomy of the genus Salmonella. In: Int. J. Syst. Evol. Microbiol. Volume 55, 2005, pp. 521-524. PMID 15653930 .
10. ^ Marieke Degen : Dangerous Darlings , DLF - Research Current , April 4, 2011 (April 8, 2011)
11. ↑ Justin Denny, J. Threlfall, J. Takkinen, S. Löfdahl, T. Westrell, C. Varela, B. Adak, N. Boxal, S. Ethelberg, M. Torpdahl, M. Straetemans and W. van Pelt: Multinational Salmonella Paratyphi B variant Java (Salmonella Java) outbreak, August – December 2007 . In: Eurosurveillance . tape 12 , no. 51 . European Center for Disease Prevention and Control (ECDC), 2007, ISSN  1025-496X , PMID 18179762 ( eurosurveillance.org [accessed February 19, 2013]).
12. ↑ Technical information - Targeting germs - Salmonella spp. LADR food analysis
13. ^ Sophia Guttenberger: The misunderstood taboo organ. Review. In: Spectrum of Science . 16. Main 2014.
14. ↑ Pete Smith: A darling, that gut! Review. In: Doctors newspaper , April 14, 2014.