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28-455: S. boydii S. dysenteriae S. flexneri S. sonnei Shigella is a genus of bacteria that is Gram negative , facultatively anaerobic , non–spore-forming , nonmotile, rod shaped , and is genetically nested within Escherichia . The genus is named after Kiyoshi Shiga , who discovered it in 1897. Shigella causes disease in primates , but not in other mammals; it

56-429: A component of dental plaque , metabolizes dietary sugar and produces acid as a waste product. The acid decalcifies the tooth surface to cause dental caries . Endotoxins are the lipid portions of lipopolysaccharides that are part of the outer membrane of the cell wall of gram-negative bacteria . Endotoxins are released when the bacteria lyses , which is why after antibiotic treatment, symptoms can worsen at first as

84-404: A natural immunity or innate resistance against many microorganisms . Pathogenic bacteria are specially adapted and endowed with mechanisms for overcoming the normal body defences, and can invade parts of the body, such as the blood, where bacteria are not normally found. Some pathogens invade only the surface epithelium , skin or mucous membrane, but many travel more deeply, spreading through

112-401: A process that is different in the pathogen from that found in the host. For example, the antibiotics chloramphenicol and tetracyclin inhibit the bacterial ribosome but not the structurally different eukaryotic ribosome, so they exhibit selective toxicity. Antibiotics are used both in treating human disease and in intensive farming to promote animal growth. Both uses may be contributing to

140-563: A research assistant at the Institute for Infectious Diseases. In 1897, Shiga focused his efforts on what the Japanese referred to as a sekiri (dysentery) outbreak. Such epidemics were detrimental to the Japanese people and occurred often in the late 19th century. The 1897 sekiri epidemic affected >91,000, with a mortality rate of >20%. Shiga studied 32 dysentery patients and used Koch's postulates to successfully isolate and identify

168-1260: A systemic inflammatory response resulting in massive vasodilation, shock, and death. Other bacteria are opportunistic pathogens and cause disease mainly in people with immunosuppression or cystic fibrosis . Examples of these opportunistic pathogens include Pseudomonas aeruginosa , Burkholderia cenocepacia , and Mycobacterium avium . Obligate intracellular parasites (e.g. Chlamydophila , Ehrlichia , Rickettsia ) are only able to grow and replicate inside other cells. Infections due to obligate intracellular bacteria may be asymptomatic , requiring an incubation period . Examples of obligate intracellular bacteria include Rickettsia prowazekii ( typhus ) and Rickettsia rickettsii , ( Rocky Mountain spotted fever ). Chlamydia are intracellular parasites. These pathogens can cause pneumonia or urinary tract infection and may be involved in coronary heart disease . Other groups of intracellular bacterial pathogens include Salmonella , Neisseria , Brucella , Mycobacterium , Nocardia , Listeria , Francisella , Legionella , and Yersinia pestis . These can exist intracellularly, but can exist outside host cells. Bacterial pathogens often cause infection in specific areas of

196-407: Is also commonly known to cause large and painful bowel movements. The stool may contain blood, mucus, or pus. Hence, Shigella cells may cause dysentery. In rare cases, young children may have seizures . Symptoms can take as long as a week to appear, but most often begin two to four days after ingestion. Symptoms usually last for several days, but can last for weeks. Shigella is implicated as one of

224-410: Is continually exposed to many species of bacteria, including beneficial commensals , which grow on the skin and mucous membranes , and saprophytes , which grow mainly in the soil and in decaying matter. The blood and tissue fluids contain nutrients sufficient to sustain the growth of many bacteria. The body has defence mechanisms that enable it to resist microbial invasion of its tissues and give it

252-630: Is the causative agent of human shigellosis . It is only naturally found in humans and gorillas. During infection, it typically causes dysentery . Shigella is a leading cause of bacterial diarrhea worldwide, with 80–165 million annual cases (estimated) and 74,000 to 600,000 deaths. It is one of the top four pathogens that cause moderate-to-severe diarrhea in African and South Asian children. Shigella species are classified by three serogroups and one serotype : Groups A – C are physiologically similar; S. sonnei (group D ) can be differentiated on

280-506: Is the most genetically divergent species of the genus Shigella . There are 19 known serotypes of Shigella boydii . S. boydii is restricted to the Indian subcontinent . The species is named after the British bacteriologist John Boyd . This Enterobacterales article is a stub . You can help Misplaced Pages by expanding it . Pathogenic bacteria#Intracellular The body

308-713: Is when the bacteria are causing little or no harm. Caused by Mycobacterium tuberculosis bacteria, one of the diseases with the highest disease burden is tuberculosis , which killed 1.4 million people in 2019, mostly in sub-Saharan Africa . Pathogenic bacteria contribute to other globally important diseases, such as pneumonia , which can be caused by bacteria such as Staphylococcus , Streptococcus and Pseudomonas , and foodborne illnesses , which can be caused by bacteria such as Shigella , Campylobacter , and Salmonella . Pathogenic bacteria also cause infections such as tetanus , typhoid fever , diphtheria , syphilis , and leprosy . Pathogenic bacteria are also

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336-537: The Shigella genomes includes a virulence plasmid that encodes conserved primary virulence determinants. The Shigella chromosomes share most of their genes with those of E. coli K12 strain MG1655. Phylogenetic studies indicate Shigella is more appropriately treated as a subgroup of Escherichia (see Escherichia coli#Diversity for details). Shigella infection is typically by ingestion . Depending on

364-688: The respiratory pathogen Haemophilus influenzae specialise in using other carbon sources such as lactate that are abundant in the human body Typically identification is done by growing the organism in a wide range of cultures which can take up to 48 hours. The growth is then visually or genomically identified. The cultured organism is then subjected to various assays to observe reactions to help further identify species and strain. Bacterial infections may be treated with antibiotics , which are classified as bacteriocidal if they kill bacteria or bacteriostatic if they just prevent bacterial growth. There are many types of antibiotics and each class inhibits

392-405: The small intestine . Shigella uses a type-III secretion system that acts as a biological syringe to translocate toxic effector proteins to the target human cell. The effector proteins can alter the metabolism of the target cell — leading, for example, to the lysis of vacuolar membranes or reorganization of actin polymerization to facilitate intracellular motility of Shigella bacteria inside

420-434: The bacteria are killed and they release their endotoxins. Exotoxins are secreted into the surrounding medium or released when the bacteria die and the cell wall breaks apart. An excessive or inappropriate immune response triggered by an infection may damage host cells. Iron is required for humans, as well as the growth of most bacteria. To obtain free iron, some pathogens secrete proteins called siderophores , which take

448-493: The bacterium causing the disease. He continued to study and characterize the bacterium, identified its methods of (Shiga-) toxin production, and worked to create a vaccine for the disease. Shigella boydii Shigella boydii is a Gram-negative bacterium of the genus Shigella . Like other members of the genus, S. boydii is a non motile , nonsporeforming, rod-shaped bacterium which can cause dysentery in humans through fecal-oral contamination. Shigella boydii

476-476: The basis of biochemical metabolism assays. Three Shigella groups are the major disease-causing species: S. flexneri is the most frequently isolated species worldwide, and accounts for 60% of cases in the developing world; S. sonnei causes 77% of cases in the developed world, compared to only 15% of cases in the developing world; and S. dysenteriae is usually the cause of epidemics of dysentery, particularly in confined populations such as refugee camps. Each of

504-487: The body. Others are generalists. The symptoms of disease appear as pathogenic bacteria damage host tissues or interfere with their function. The bacteria can damage host cells directly or indirectly by provoking an immune response that inadvertently damages host cells, or by releasing toxins . Once pathogens attach to host cells, they can cause direct damage as the pathogens use the host cell for nutrients and produce waste products. For example, Streptococcus mutans ,

532-523: The cause of high infant mortality rates in developing countries . A GBD study estimated the global death rates from (33) bacterial pathogens, finding such infections contributed to one in 8 deaths (or ~7.7 million deaths), which could make it the second largest cause of death globally in 2019. Most pathogenic bacteria can be grown in cultures and identified by Gram stain and other methods. Bacteria grown in this way are often tested to find which antibiotics will be an effective treatment for

560-459: The hemolytic Shiga toxin , similar to the verotoxin produced by enterohemorrhagic E. coli . Both Shiga toxin and verotoxin are associated with causing potentially fatal hemolytic-uremic syndrome . Because they do not interact with the apical surface of epithelial cells — preferring the basolateral side — Shigella species invade the host through the M-cells interspersed in the epithelia of

588-585: The host cell. For instance, the IcsA effector protein (an autotransporter, not a type-III secretion-system effector) triggers actin reorganization by N-WASP recruitment of Arp2/3 complexes , promoting cell-to-cell spread. After infection, Shigella cells multiply intracellularly and spread to neighboring epithelial cells, resulting in tissue destruction and the characteristic pathology of shigellosis. The most common symptoms are diarrhea , fever , nausea , vomiting , stomach cramps , and flatulence . Infection

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616-501: The host's health, fewer than 100 bacterial cells may cause an infection. Shigella species generally invade the epithelial lining of the colon , causing severe inflammation and death of the cells lining the colon. This inflammation produces the hallmark diarrhea — even dysentery — of Shigella infection. Toxins produced by some strains contribute to disease during infection. S. flexneri strains produce ShET1 and ShET2, which may contribute to diarrhea. S. dysenteriae strains produce

644-482: The infection. For hitherto unknown pathogens, Koch's postulates are the standard to establish a causative relationship between a microbe and a disease. Each species has specific effect and causes symptoms in people who are infected. Some people who are infected with a pathogenic bacteria do not have symptoms. Immunocompromised individuals are more susceptible to pathogenic bacteria. Some pathogenic bacteria cause disease under certain conditions, such as entry through

672-455: The iron away from iron-transport proteins by binding to the iron even more tightly. Once the iron-siderophore complex is formed, it is taken up by siderophore receptors on the bacterial surface and then that iron is brought into the bacterium. Bacterial pathogens also require access to carbon and energy sources for growth. To avoid competition with host cells for glucose which is the main energy source used by human cells, many pathogens including

700-499: The pathogenic causes of reactive arthritis worldwide. The Shigella genus is named after Japanese physician Kiyoshi Shiga , who researched the cause of dysentery. Shiga entered the Tokyo Imperial University School of Medicine in 1892, during which he attended a lecture by Shibasaburo Kitasato . Shiga was impressed by Kitasato's intellect and confidence, so after graduating, he went to work for him as

728-572: The rapid development of antibiotic resistance in bacterial populations. Phage therapy , using bacteriophages can also be used to treat certain bacterial infections. Infections can be prevented by antiseptic measures such as sterilizing the skin prior to piercing it with the needle of a syringe and by proper care of indwelling catheters. Surgical and dental instruments are also sterilized to prevent infection by bacteria. Disinfectants such as bleach are used to kill bacteria or other pathogens on surfaces to prevent contamination and further reduce

756-436: The skin via a cut, through sexual activity or through compromised immune function. Some species of Streptococcus and Staphylococcus are part of the normal skin microbiota and typically reside on healthy skin or in the nasopharyngeal region. Yet these species can potentially initiate skin infections. Streptococcal infections include sepsis , pneumonia , and meningitis . These infections can become serious creating

784-448: The tissues and disseminating by the lymphatic and blood streams . In some rare cases a pathogenic microbe can infect an entirely healthy person, but infection usually occurs only if the body's defence mechanisms are damaged by some local trauma or an underlying debilitating disease, such as wounding, intoxication , chilling , fatigue, and malnutrition . In many cases, it is important to differentiate infection and colonization , which

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