Shigella
| Shigella | ||||||||||||
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Shigella boydii |
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| Scientific name | ||||||||||||
| Shigella | ||||||||||||
| Castellani and Chalmers 1919 | ||||||||||||
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The bacteria of the genus Shigella (also known as Shigella) are a group of gram-negative rod-shaped bacteria of the enterobacteria family (Enterobacteriaceae). They cause the sometimes very severe bacterial agitation with diarrhea. They were named by Aldo Castellani and AJ Chalmers after the Japanese bacteriologist Kiyoshi Shiga , the discoverer of the bacterial dysentery pathogen (evidence publication 1898). The bacteria are immobile and can live without the presence of oxygen ( optionally anaerobic ). Shigellosies are notifiable .
Epidemiology and Sources of Infection
The four known Shigella species groups are all medically relevant as pathogens of Shigellosis (bacterial dysentery ) and have so far only been detected in humans and primates. Around 160 million people are infected worldwide each year, of which around 1 million die. These are mostly children, elderly and immunocompromised patients. (Source missing)
They are spread by polluted water or food, sometimes also by flies. The disease symptoms (mainly fever and severe diarrhea , but also arthritis) are a response to the migration of the bacteria in the intestinal tissue and the secretion of Shigella enterotoxins . The Shigella infection (including bacterial dysentery or bacterial dysentery ) is in the primary immune response Macrophages and neutrophilic granulocytes are weakened, for which the latter produce the enzyme elastase-2 (gen .: ELANE).
Pathogenicity factors
Shigella dysenteriae produce the so-called Shiga toxin as a pathogenicity factor , which leads to more severe poisoning than in infections with other Shigella groups (hemolytic course).
Shigella also produce a protein-digesting enzyme called VirA , which acts on the building blocks of the microtubules ( tubulin ) of the infecting cells. VirA slits open the microtubules so that the shigellae can penetrate them. Shigella move non-directionally in the cytosol of the host cell by polar actin polymerization.
Shigella species groups
- Group A, Shigella dysenteriae : Group A bacteria are mainly found in the tropics and subtropics. Infections with serotype A (also known as the Shiga Kruse bacterium) are particularly severe, as these bacteria form nerve toxins in addition to normal toxins .
- Group B, Shigella flexneri : Infections in this group are generally less severe than those in group A; the bacteria are spread worldwide. It is currently under discussion whether infections with these bacteria are related to some cases of sudden infant death syndrome. Shigella flexneri was sequenced in 2002 , so the genome is fully known.
- Group C, Shigella boydii : Boyd bacteria are found mainly in the Middle East and North Africa, infections with them are rare and mostly harmless.
- Group D, Shigella sonnei : These species, also known as Kruse-Sonne bacteria, are the most common Shigella, especially in Central Europe, and cause harmless summer diarrhea , especially in children .
Diagnosis
Shigella are cultured from stool samples. XLD agar is often used as the nutrient medium , sometimes after a short pre-incubation of the sample (approx. 6 hours) in selenite broth. Suspicious colonies show the following properties on XLD agar: no discoloration of the originally red agar towards yellow, no black discoloration of the colonies (H 2 S negative), oxidase negative (differentiation from Pseudomonas aeruginosa ), in the further differentiation (urea broth) Urease negative (differentiated from Proteus, Morganella and Providencia spp.). If there is a corresponding suspicion, this must be confirmed using biochemical and serological methods. In particular, the differentiation of enteroinvasive strains of Escherichia coli can sometimes be difficult, since Shigella are very closely related to E. coli in terms of developmental history and sometimes also biochemically. According to the current taxonomy of bacteria, Shigella should actually be included in the E. coli species and, as a pathovar, be distinguished from other strains of this species. However, for historical and clinical reasons, this has not yet been done.
treatment
Infections caused by bacteria of the genus Shigella should usually be treated with antibiotics. Fluoroquinolones such as ciprofloxacin or levofloxacin are often used as standard in adults , along with azithromycin , cotrimoxazole , doxycycline and ampicillin . Treatment with a third generation cephalosporin (e.g. ceftriaxone or cefixime ) is also recommended in children . It is necessary to adapt the antibiotic therapy to the antibiogram of the pathogen detected. By treating epidemics in developing countries, resistant strains are spreading, making epidemics increasingly difficult to control.
prevention
The key to avoiding Shigella infections lies primarily in good drinking water, food and hand hygiene , as the bacteria are excreted with the stool and in this way are transmitted directly (“faecal-oral”) or indirectly (via drinking water or food) . A special feature of Shigella compared to many other diarrheal pathogens (e.g. Salmonella ) is the low infectious dose of around 100 bacteria, which can lead to the transmission of the disease. Therefore, particularly strict hygiene measures are required to contain shigella outbreaks. This is also the reason that Shigella outbreaks can occur as a result of special sexual practices.
Reporting requirement
In Germany, the direct or indirect detection of Shigella sp. Specifically notifiable in accordance with Section 7 of the Infection Protection Act (IfSG), provided that 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 analysis results for Shigella spp. Notifiable for laboratories according to the Epidemics Act (EpG) in conjunction with the Epidemics Ordinance and Appendix 3 of the EDI Ordinance on the reporting of observations of communicable diseases in humans .
Individual evidence
- ↑ lexikon-orthopaedie.com: Shigella arthritis
- ↑ Lois J. Paradise, Mauro Bendinelli, Herman Friedman: Enteric infections and immunity. Springer, 1996 ISBN 0-306-45242-1 p. 79ff.
- ^ Research Highlights in Nature Bnd. 444, p. 246, Nov. 16, 2006 about an article in Science Bnd. 314, pp. 985-986, 2006
- ↑ a b Helmut Tschäpe, Rolf Reissbrodt and Rita Prager: Shigella spp. In: Birgid Neumeister, Heinrich K. Geiss, Rüdiger W. Braun and Peter Kimmig (eds.): Microbiological diagnostics . 2nd Edition. Thieme, Stuttgart, New York 2009, ISBN 978-3-13-743602-7 , pp. 449-450 .
- ↑ a b Shigellosis: RKI advice for doctors. Robert Koch Institute , May 8, 2012, accessed February 15, 2013 .
- ↑ Herbert L. DuPont: Shigella Species (Bacillary Dysentery) . In: Gerald L Mandell, John E. Bennett and Raphael Dolin (Eds.): Principles and Practice of Infectious Diseases . 7th edition. Churchill Livingstone Elsevier, Philadelphia 2010, ISBN 978-0-443-06839-3 , pp. 2905-2910 .
- ↑ sonnenlaender.de: Shigellosis (bacterial dysentery)