Шигелла: возбудитель дизентерии и причины шигеллёза

Genus of bacteria
the genus

Shigella is a genus of bacteria that is Gram negative, facultatively anaerobic, non–spore forming, nonmotile, rod shaped, and is genetically closely related to Escherichia. The genus is named after Kiyoshi Shiga, who discovered it in 1897. Shigella causes disease in primates, but not in other mammals; it 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) It is one of the top four pathogens that cause moderate to severe diarrhea in African and South Asian children.

Shigella infection is typically by ingestion. Depending on 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. 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 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 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 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 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 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.