|van Loghem , 1944|
Yersinia is the name of a genus of gram-negative , mostly rod-shaped bacteria fromthe Enterobacteriaceae family . In the plural , representatives of the genus " Germanized " are also referred to as Yersinia . According to the code of the nomenclature of bacteria , the grammatical gender of the generic name is feminine. As is typical for members of the Enterobacteriaceae family, Yersinia reproducesunder facultative anaerobic conditions. The species Yersinia pestis , Yersinia pseudotuberculosis and Yersinia enterocolitica are of medical importance for humans; other Yersinia species can cause diseases in animals. There are also representatives of the genus that exist in the environment, e.g. B.to be foundin waters and soils and are not pathogenic ("pathogenic").
The generic name was chosen in honor of the Swiss bacteriologist Alexandre Émile Jean Yersin . In 1894 he conducted research in Hong Kong for the causative agent of the plague . He succeeded in isolating the pathogen from infected lymph nodes ( bubones ) from plague deaths and in transmitting the disease to mice , rats and guinea pigs . At the same time, the Japanese bacteriologist Kitasato Shibasaburō was researching the pathogen in Hong Kong and was able to isolate it from the blood. In the further course of the investigations, the bacterial cultures were contaminated by pneumococci . For this reason, Yersin is mentioned in many literature sources as the discoverer, while others independently attribute the discovery to two scientists.
The representatives of the genus Yersinia are gram-negative bacteria, they do not form persistent forms such as endospores . Several species are capable of active movement through flagella . The flagellation is only formed in a certain temperature range during its cultivation . The cells of Yersinia species are rod-shaped , varying in size, so that they are described as pleomorphic rods or cocoid rods. Some Yersinia species have a capsule that is superimposed on the bacterial cell wall. a. the case with Yersinia pestis . Within one species there may be strains of bacteria that have a capsule, while other strains do not. This is the case with Y. enterocolitica , for example . The capsule acts as an antigen .
Growth and metabolism
The cells grow facultatively anaerobically , so they can multiply even if there is no oxygen . They are catalase positive and oxidase negative. The optimal temperature for growth is 20–37 ° C, so the representatives of the genus Yersinia belong to the mesophilic (medium temperature preferring) bacteria. The temperature during cultivation has an effect on the cell morphology of some Yersinia species . Y. pestis forms a capsule at 37 ° C, while this does not happen at lower temperatures (28–30 ° C). Y. pseudotuberculosis only shows flagellation if the temperature during cultivation is below 30 ° C. In addition, several species tolerate significantly lower temperatures and are still able to reproduce at 4 ° C, e.g. B. Y. enterocolitica .
Yersinia operates a chemoorganotrophic and heterotrophic metabolism , it uses organic compounds as an energy source and also to build up the cell's own substances. The metabolism is typical for the representatives of the Enterobacteriaceae, different substrates are used in one fermentation . For example, the carbohydrates glucose and arabinose are broken down into acids and other products by fermentation. Gas is not formed in the process. Lactose is not broken down. In contrast, the sugar alcohol mannitol is used with acid formation. Most Yersinia species have the enzyme urease and can therefore utilize urea . They are also able to reduce nitrate to nitrite with the help of the enzyme nitrate reductase (NADH) . However, they do not have the enzyme lysine decarboxylase (LDC), which enables the release of carbon dioxide (CO 2 ) from the amino acid lysine . Hydrogen sulphide (H 2 S) is not formed, nor is indole, the indole test is negative. The Voges-Proskauer test is negative for most species; no acetoin is formed. Further metabolic reactions, such as the occurrence of the enzyme ornithine decarboxylase (ODC) or the utilization of various carbohydrates and sugar alcohols (e.g. sorbitol ) with acid formation can be checked in a colorful series to identify the species from each other and from other representatives of the Enterobacteriaceae family distinguish.
The GC content (the proportion of the nucleobases guanine and cytosine ) in the bacterial DNA is between 46 and 50 mol percent . This is comparable to the GC content in the DNA of Escherichia coli and other Enterobacteriaceae. Yersinia pestis has been one of the sequenced organisms since 2001 ; the genome of the bacterium is fully known. In addition to the bacterial chromosome , it also includes three plasmids . By 2014 the genome of eleven other species had been sequenced, in chronological order Y. pseudotuberculosis , Y. bercovieri , Y. frederiksenii , Y. intermedia , Y. mollaretii , Y. enterocolitica , Y. aldovae , Y. kristensenii , Y. rohdei , Y. ruckeri , and Y. similis . One or more plasmids were found in Y. enterocolitica , Y. frederiksenii , Y. pseudotuberculosis , Y. ruckeri , and Y. similis .
The genus Yersinia includes both human and animal pathogenic (“disease-causing”) species as well as species that are non-pathogenic. These include, for example, Y. aldovae and Y. mollaretii , they are assigned to risk group 1 by the Biological Agents Ordinance in conjunction with the TRBA ( Technical Rules for Biological Agents) 466 . Most species are assigned to risk group 2, that is, they are classified as pathogenic. B. the zoonotic pathogens Y. enterocolitica , Y. frederiksenii and Y. pseudotuberculosis . Only Y. pestis is assigned to risk group 3, which is characterized by the fact that the infectious disease caused has more serious consequences.
A special feature of the Yersinia species is that they secrete numerous proteins, i.e. release them from the cell to the environment. These proteins are called YOP ( English Yersinia outer protein , “outer proteins of Yersinia ”) or YOPs or Yops in the plural. They act as virulence factors in the pathogenic species because they have, for example, anti-phagocytic properties; H. the phagocytosis as part of the immune system prevent. The genes that code for these proteins are on a plasmid. Apathogenic species or strains lack this plasmid.
Various pathogenic Yersinia species form siderophores . These are low molecular weight compounds that bind iron (III) ions through complexation and thereby promote the iron supply of the bacteria. A well-known representative is the siderophore known as Yersiniabactin (Ybt), which can be found in Y. pestis , Y. pseudotuberculosis and some strains of Y. enterocolitica . The mode of action as a virulence factor has not yet been conclusively clarified. However, the disturbed biosynthesis of yersiniabactin leads to a significant reduction in virulence in the affected strains . In addition, the expression of the ybt genes in bacteria that have infected cells of mammals is increased compared to the bacteria that are cultivated in a nutrient medium . In Y. pseudotuberculosis further siderophores were discovered as Pseudochelin (Pch) and Yersiniachelin be called (Ych) and on the other also in the genome of Yersinia styles are coded. However, the expression of a functional siderophore could not yet be detected there.
The samples can be clinical material (e.g. blood , sputum , stool or secretion extracted from the lymph nodes in the case of bubonic plague , the lymph node aspirate or bubonic aspirate) or food , water or other samples from the environment that may be Yersinia contain. In the latter, an enrichment of the bacteria is usually necessary, a liquid nutrient broth containing peptone , sorbitol and bile salts is used, it is also abbreviated as PSBB (English for Peptone Sorbitol Bile Broth ). In principle, all nutrient media that are used as selective media for Enterobacteriaceae are suitable for cultivation , for example MacConkey agar or eosin methylene blue agar. Likewise, blood agar be used, which is there to no hemolysis occurs. A Yersinia selective medium is also available, which is called Cefsulodin-Irgasan-Novobiocin-Agar (CIN-Agar) after three of the components it contains. It should be noted that activities with Y. pestis in which the pathogen is multiplied may only be carried out in a laboratory of protection level 3 . A “colorful series” is then carried out with the colonies that have grown on the culture media in order to identify the species (see Growth and Metabolism ). A rapid determination system based on this in miniature format ( Analytical Profile Index ) for the determination of bacteria from the Enterobacteriaceae families is commercially available.
In the case of Y. enterocolitica , this procedure is not sufficient, since other Yersinia species cannot be differentiated from it by the biochemical characteristics of the Bunte series. Here the assignment to the serotypes by means of an agglutination test makes sense. A polyvalent O-specific antiserum is used, which leads to agglutination with sample material which contains O-antigens from Y. enterocolitica . The detection of Yersinia TYPES may also by serological done methods based on the antigen-antibody reaction based. Antibodies that have been formed against the YOPs can be detected from clinical samples . The ELISA method (quantitative detection) or a Western blot is carried out for this purpose.
The habitat of Y. aldovae is water. Y. bercovieri was found mainly in patients with diarrhea , and also in uncooked foods and environmental samples. Y. enterocolitica is native to bodies of water and is also widespread in the animal kingdom. It can be found in the intestines of mammals, less often in insects and amphibians . In terms of food transmission, pork is of great importance. Y. frederiksenii has been isolated from freshwater , sewage and soil, wild animals and domesticated animals are also part of its habitat and it has been found in food and in sick and healthy people. The same applies to Y. intermedia , which was isolated from fresh water and animals living in it, wild animals and domesticated animals, food, and healthy and sick people (diseases of the digestive tract ).
Y. kristensenii was also isolated from samples from the environment, from food, animals and sick and healthy people; the same applies to Y. mollaretii . For Y. pestis since the Enlightenment of the sources of infection and routes of infection of the plague known that they in rodents , such as the black rat is found, and fleas as vectors is widespread. Y. pseudotuberculosis is native to bodies of water and causes gastroenteritis in many animal species and in humans . Y. rohdei has been isolated from the feces of dogs and humans and is native to bodies of water . Y. ruckeri was from the rainbow trout ( Oncorhynchus mykiss isolated), in which it causes the disease "enteric red mouth disease", the economic damage in the aquaculture of salmonids caused. The habitat of Y. similis are soils.
The genus Yersinia belongs to the family of Enterobacteriaceae in the order of Enterobacteriales that the class of Gammaproteobacteria belongs. The family comprises more than 40 genera (as of 2014), with Escherichia as the type genus . Many representatives are typical intestinal inhabitants. Common features are that they behave gram-negative in Gram staining and their metabolism is facultatively anaerobic.
The following species and subspecies are known (as of 2014):
- Yersinia aldovae Bercovier et al. 1984
- Yersinia aleksiciae Sprague & Neubauer 2005 (Through the investigation of phenotypically different strains of Y. kristensenii it was discovered that these represent a species of their own.)
- Yersinia bercovieri Wauters et al. 1988
Yersinia enterocolitica ( Schleifstein & Coleman 1939) Frederiksen 1964
- Yersinia enterocolitica subsp. enterocolitica ( Schleifstein & Coleman 1939) Neubauer et al. 2000
- Yersinia enterocolitica subsp. palearctica Neubauer et al. 2000
- Yersinia entomophaga Hurst et al. 2011
- Yersinia frederiksenii Ursing et al. 1981
- Yersinia intermedia Brenner et al. 1981
- Yersinia kristensenii Bercovier et al. 1981
- Yersinia massiliensis Merhej et al. 2008
- Yersinia mollaretii Wauters et al. 1988
- Yersinia nurmii Murros-Kontiainen et al. 2011
- Yersinia pekkanenii Murros-Kontiainen et al. 2011
- Yersinia pestis ( Lehmann & Neumann 1896) van Loghem 1944
- Yersinia pseudotuberculosis ( Pfeiffer 1889) Smith & Thal 1965
- Yersinia Rohdei Aleksic et al. 1987
- Yersinia ruckeri Ewing et al. 1978
- Yersinia similis Sprague et al. 2008
Several species are so closely related to Y. enterocolitica that they can hardly be distinguished from one another on the basis of their phenotypic characteristics and in some cases were previously classified in "subgroups" (without taxonomic rank). These include Y. aldovae , Y. aleksiciae , Y. bercovieri , Y. frederiksenii , Y. kristensenii and Y. mollaretii . Due to its biochemical properties, Y. intermedia represents an "intermediate link " ( Latin intermedia ) between Y. enterocolitica and Y. pseudotuberculosis . While Y. similis (Latin similis , "similar") is so similar in biochemical characteristics to Y. pseudotuberculosis , that they cannot be distinguished by a colored row. By examining several household genes from Y. pestis and comparing them with related species, it was shown that the plague pathogen originates as a clone of Y. pseudotuberculosis . The development began 1,500 to 20,000 years ago, a short period of time in terms of evolution .
Species of importance for human medicine
Yersinia enterocolitica is the causative agent of febrile intestinal inflammation ( enterocolitis or enteritis ) as a result of a food infection . Side effects such as extensive erythema nodosum , Yersinia arthritis or Reiter's disease with eczema of the palms of the hands and soles of the feet often occur .
Yersinia pseudotuberculosis is a rod-shaped bacterium, which is characterized by a peritric flagellation. However, the flagella are only formed if the temperature during cultivation is below 30 ° C. Y. pseudotuberculosis causes a disease with tuberculosis- like symptoms in rodents ( rodentiosis ), rabbits , canines and birds . Even ungulates can develop diarrheal diseases with emaciation and jaundice . In humans, mesenteric lymphadenitis is clinically evident , which is difficult to distinguish from appendicitis and is therefore also referred to as pseudoappendicitis .
Yersinia pestis is the causative agent of the plague . It is an immobile rod without flagella, capable of splitting urea. Various microbial toxins and virulence factors produced by the bacterium are important in infection with Y. pestis . Mostly there is lymphogenic spread of the Yersinia, clinically recognizable by characteristic blue-black, tender bumps (bubons). If it spreads into the bloodstream, sepsis results , if spread into the lungs, secondary pulmonary plague with highly infectious sputum results . As primary pulmonary plague, the disease is almost always fatal if left untreated; the mortality rate of bubonic plague is given as 50–60%. The diagnosis of plague is made by detecting the pathogen in the bubonic aspirate, sputum or blood. Microscopy of clinical samples and detection methods after culturing the bacteria are used.
In Germany, the direct or indirect detection of Yersinia pestis and of Yersinia spp. Specifically subject to reporting in accordance with the Infection Protection Act , provided the evidence indicates an acute infection.
In Switzerland, the positive and negative laboratory analysis findings to be Yersinia pestis notifiable and that after the Epidemics Act (EpG) in connection with the epidemic Regulation and of the Regulation of EDI on the reporting of observations of communicable diseases of man .
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