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1 edited by He Shilin 1 Introduction to medical research methods 1*:* Health Press 1 199865438 edited by Liang Wannian 1 medical research methodology 1*:* Health Press/kloc-.
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Article number:1671-4695 (2005) 02-0123-02.
Research progress of enterohemorrhagic Escherichia coli enteritis
Shi Chongming Chi Ruohong Wang Baohua
(Yantai Health and Epidemic Prevention Station, Yantai, Shandong 64000)
Enterohemorrhagic Escherichia coli o 157∶h7 infectious diarrhea.
It is a serious intestinal infectious disease newly discovered in recent years. The disease can cause diarrhea, hemorrhagic enteritis, secondary hemolytic uremic syndrome (hus), thrombotic thrombocytopenic purpura (ttp) and so on. Hus and ttp have dangerous conditions and high mortality. The clinical research progress of hemorrhagic colitis caused by e2heco 157∶h7 in recent years is introduced as follows. 1 epidemiology
2 Etiology and pathogenic factors
Eheco 157∶h7 Gram staining was negative, except that it was not fermented or slow.
Except for fermented sorbitol, the common biochemical characteristics are similar to those of other Escherichia coli. It can survive for 5 hours at 37℃ with pH 2 1 5 or ph3 10, and can be killed when heated above 75℃1min. Many eheco 157∶h7 contain transferrin, which is beneficial to its growth and reproduction in human body.
A remarkable feature of eheco 157∶h7 is that it can produce a large number of records.
Sal-like toxin (slt) has neurotoxicity and cytotoxicity.
2〕
And intestinal toxicity [according to its antigenicity and immunity, etc.
Riley and others in the United States have suffered from hemorrhagic colitis since 1983.
Since eheco 157∶h7 was isolated from the epidemic, o 157 has been distributed and broke out in Canada, Britain, Germany, Australia, Japan and Africa. Hemorrhagic colitis (hc) caused by o 157 occurred from 1986 to 1988 in Xuzhou City, Jiangsu Province, China. O 157 was first reported in the whole country, and then o 157 was detected from bloody feces of patients in Shandong, Tianjin and Xinjiang.
Eheco 157∶h7 mainly causes sporadic infection and can also cause outbreaks. The peak of the disease is from July to August, and it can occur at any age, but the incidence of children and the elderly is significantly higher than that of other age groups, and it is easy to be complicated with hus and ttp. Cattle is one of the main sources of infection. o 157 can be detected in the feces of both diarrhea and healthy cattle, and patients and carriers are the more important sources of infection. Bacteria are excreted with animal or human feces and spread directly or after food or water in secondary pollutant, so it is one of intestinal infectious diseases.
〔 1〕
Slt is also divided into slt 1 and slt2. The main difference between them is that slt2 is not neutralized by Shiga toxin antiserum, so it is very toxic.
Play an important role in the disease. In addition, all eheco 157∶h7 have a large plasmid of 65mda, and some substances encoded by this plasmid, such as fimbriae and hemolysin, also have certain pathogenic effects. 3 Pathogenesis
The pathogenesis is mainly through the adhesion of bacteria to epithelial cells and the production of toxins. 3 1 1 adhesion
When enterohemorrhagic Escherichia coli invades the intestinal cavity, it locally adheres to the brush-like edges of cecum and colon epithelial cells with the help of fimbriae and damages microvilli, and at the same time closely binds to the top of intestinal epithelial cell membrane. 3 12 toxin
Slt toxin is mediated by glycolipid receptor gb3 in intestinal wall cells.
After the target cell enters the cell, it inhibits the synthesis of protein. because
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Gb3 receptor exists widely in vascular endothelial cells, intestinal epithelial cells and kidneys.
And nerve tissue cells, so these cells are poisoned by slt.
The influence of elements [2]
, damage the colonic epithelial cells, resulting in hemorrhagic colitis; Hus is caused by destroying vascular endothelial cells, red blood cells and platelets. Kidney damage will lead to extensive tubular necrosis and acute renal failure. Toxins enhance the excitability of parasympathetic nerve, leading to sinus tachycardia and convulsion. Slt toxin can also stimulate
Endothelial cells release factor VIII, which leads to ttp. 4 Clinical manifestations and prognosis
The incubation period after o 157 infection is 3 ~ 4 days, and the longest is 10 days.
Clinical manifestations vary in severity, and mild symptoms are often atypical, such as abdominal pain, watery stool without blood, low or moderate fever, upper respiratory symptoms, etc. Most of them are cured within 5 ~ 10 days. A few mild patients, especially children under 5 years old and the elderly, will have complications a few days after onset. In severe cases, the onset is sudden, and soon abdominal pain and watery stool appear, and then bloody stool can be seen by the naked eye. About 7% patients with severe infection are complicated with hus and ttp. The triad of hus is microvascular hemolytic anemia,
Thrombocytopenia and acute renal failure. The clinical manifestation is obvious poverty.
Blood, skin and mucous membrane bleeding, hematemesis, bloody stool, hematuria, oliguria or anuria, etc. Early reports showed that the mortality rate was as high as 30% ~ 50%. In recent years, due to the improvement of diagnosis and treatment, the mortality rate has dropped to about 5%. Another serious complication is ttp. Besides thrombocytopenic purpura, there are microangiopathic hemolytic anemia and nervous system complications.
The mortality rate can also reach 50% [3]
. 5 laboratory inspection methods
Isolation, culture and serological identification of 5 1 1o 157
It is best to take stool samples from patients at the early stage of the disease and before antibiotic treatment, and directly inoculate patients' blood stool on selective medium as soon as possible. At present, the widely used selection medium is sorbitol MacKay agar (smac) proposed by march et al., and EHEC is on SMAC agar.
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It is a colorless colony, while other Escherichia coli that ferment sorbitol is a pink colony. Then the culture is taken and the slide agglutination test is made with o 157 and h7 serum, and the diagnosis can be made. 5 12 polymerase chain reaction
O 157 has a large plasmid of 65mda. According to plasmid
Primers designed with specific sequences can quickly detect hemolysin gene by pcr, and can detect o 157 and non-o 157 enterohemorrhagic Escherichia coli. In addition, the gene slt5 of Shiga-like toxin can be detected by pcr to detect slt-producing Escherichia coli. 6 treatment
Bacterial o 157 is effective against compound sulfamethoxazole, furazolidone and nitrofurantoin.
Antibiotics, such as antibiotics and cefotaxime, are highly sensitive and can be used appropriately in the early stage to improve symptoms, prevent complications of hus and ttp and exclude carriers. Once hus and ttp appear, antibiotics are not recommended, and the therapeutic effect of adrenocortical hormone is not good. At this time, it is necessary to carry out intensive care and symptomatic treatment. If necessary, plasma infusion, plasma exchange, antithrombosis, intravenous immunoglobulin and its application should be adopted.
Toxin inhibitors and other treatments. Ampicillin is ineffective [4]
. To sum up, o 157 is a newly discovered Escherichia coli causing hemorrhagic colitis in recent years, and it is one of the pathogens of intestinal infectious diseases. Medical workers in China should improve their understanding of o 157 infectious diarrhea and take comprehensive preventive measures in time to avoid the outbreak. refer to
1 Study on hemorrhagic enteritis caused by Wang Li, Yang, Huang.
Exhibition 1 American Chinese Journal of Internal Medicine, 200 1, 3 (2):148-1491.
2ts chapeh 1 cytotoxic Escherichia coli 157:H7 binds to haemor2.
rhagiolitisincanada 1 kinderarztlprax， 199 1.59(6): 16 1- 165 13 Riley lw 1 heepidemiologio， clinical and microbiological featuresof haemor 2 rhagiolitis 1 annrevmicrobiol， 1987，
4 Xiao Shudong 1 Intestinal Inflammation and Infectious Diseases 1 Gastroenterology 1 Shanghai Science and Technology Press
She, 200 1, 382 1