Enterohemorrhagic Escherichia coli infection

Brief introduction of enterohemorrhagic Escherichia coli infection An intestinal infectious disease caused by enterohaemorrhagic Escherichia coli (EHEC). EHEC is the pathogen of hemorrhagic enteritis, mainly Escherichia coli O157:H7, which is a newly discovered diarrhea-causing Escherichia coli. In addition, O26:H11 may also be one of the pathogens. There is no official report yet in China. basic knowledge Sickness ratio: 12% Susceptible people: no specific people Mode of infection: non-infectious Complications: uremia thrombotic thrombocytopenic purpura

Causes of enterohemorrhagic Escherichia coli infection

Causes:

Escherichia coli O157:H7 is different from other serotypes of Escherichia coli and grows well at 30-42 °C, but the optimal growth temperature is still 37 °C. The slow-fermented sorbitol-McKay (SMAC) medium can be used as For the screening medium of O157:H7, on the SMAC medium, the O157:H7 colonies were colorless, while the fermentation strains were pink, but half of the EPEC strains were similar to O157:H7, and the identification of EPEC and EHEC should be noted. Escherichia coli O157:H7 acid and low temperature resistance, pH 2.5 ~ 3.5, temperature 37 ° C, can withstand 5h without loss of activity, long-term survival in the refrigerator, not heat, 75 ° C 1min is killed, the large intestine Escherichia coli O157:H7 does not contain the general enterotoxin gene code, and does not produce LT, ST by gene probe and animal test. It is not invasive, does not belong to EPEC serotype, and can produce a large number of Shiga-like toxins (Shiga- Like toxin (SLT), SLT is antigenic and can be neutralized by the rabbit antiserum of Shiga type I toxin. Because SLT can denature, dissolve and die of Vero cells (ie, African green monkey kidney cells), it is also called It is Veto toxin, referred to as VT, among the toxins produced by bacteria, V T is one of the strongest toxins. It can be inactivated by heating at 98 ° C for 15 min. It is divided into VT1 and VT2 according to different antigenicity. The structure is composed of 1 A subunit and 5-6 B subunits. The molecular weights were 3,300 and 8,000, respectively.

Pathogenesis:

EHEC invades the human body from the oral cavity. After reaching the intestinal lumen, it adheres to the brush border of the intestinal villi with the help of pili. The B subunit binds to the intestinal epithelial cell glycolipid receptor GB3, and the A subunit has toxin activity and enters the cell. And inhibit protein synthesis, damage intestinal epithelial cells, the focus is on the cecum and colon, visible diffuse hemorrhage of the intestinal mucosa, ulcers, in addition to intestinal epithelial cells, GB3 receptors are also widely present in vascular endothelial cells, kidney and nerve tissue cells, damage to blood vessels Endothelial cells, red blood cells and platelets cause HUS. Extensive tubular necrosis can lead to acute renal failure. The excitability of parasympathetic nerves is enhanced by the action of toxins, sinus bradycardia and convulsions can occur, and Vero toxin also stimulates endothelial cell release. Factor VIII, which leads to thrombotic thrombocytopenic purpura.

Enterohemorrhagic Escherichia coli infection prevention

Prevention of this disease, in addition to common with other intestinal infectious diseases such as washing hands before and after meals, to protect food water source hygiene, the focus should be on the management of frozen fast food, to prevent food contamination, to fully heat before eating.

Enterohaemorrhagic Escherichia coli infection complications Complications uremia thrombotic thrombocytopenic purpura

Concomitant hemolytic uremic or thrombotic thrombocytopenic purpura.

Intestinal hemorrhagic Escherichia coli infection symptoms Common symptoms Abdominal pain coma low fever jaundice diarrhea nausea intestinal bleeding less urine hematuria watery stool

The incubation period is 1 to 14 days, usually 4 to 8 days. Before the illness, there may be a history of processing frozen foods in semi-finished products. There are three clinical types of asymptomatic infection, mild diarrhea and hemorrhagic enteritis. The typical manifestation is acute onset. , diarrhea, the first watery stool, followed by bloody stool, with abdominal pain, no fever or low fever, may be associated with nausea, vomiting and sensation-like symptoms, no comorbidities, 7 to 10 days of natural recovery, a small number of patients In the course of 1 to 2 weeks, secondary hemolytic-uremic syndrome (HUS), manifested as pale weakness, hematuria, oliguria, anuria, subcutaneous mucosal hemorrhage, jaundice, coma, convulsions, etc., more common in the elderly , children, immune function is low, the mortality rate is 10% to 50%.

Examination of enterohemorrhagic Escherichia coli infection

1. Bacterial culture separation to improve the positive rate of stool culture can improve the diagnosis rate, affecting the factors of culture, mainly stool characteristics, disease course and medium selection, bloody stool, short course of disease, high positive rate; watery stool, long course In particular, for more than 7 days, the positive rate is low, and sorbitol-McConkai agar (SMAC) can increase the positive rate.

2. Immunological detection Direct ELISA was performed using a monoclonal antibody to detect O157:H7 Escherichia coli.

3. Gene detection using EHEC-specific DNA probes, the sensitivity and specificity can reach 99%; or PCR analysis of EHEC DNA sequence, found that its hemolysin AB gene is unique to EHEC, its specificity, sensitivity and rapid The results of 3~4h can be found. Other multiplex PCR methods for simultaneous amplification of two pairs of oligonucleotide primers, SLT1 and SLT2, have not been widely used in clinical practice. Genetic testing can be used for clinical research and epidemiological investigation.

X-ray examination showed submucosal edema of the ascending colon and the model colon.

Diagnosis and diagnosis of enterohemorrhagic Escherichia coli infection

In addition to epidemiological and clinical features, O157:H7 Escherichia coli and its toxins can be diagnosed from the stool. The identification methods are as follows:

1. Bacterial culture separation to improve the positive rate of stool culture can improve the diagnosis rate, affecting the factors of culture, mainly stool characteristics, disease course and medium selection, bloody stool, short course of disease, high positive rate; watery stool, long course In particular, for more than 7 days, the positive rate is low, and sorbitol-McConkai agar (SMAC) can increase the positive rate.

2. Immunological detection Direct ELISA was performed using a monoclonal antibody to detect O157:H7 Escherichia coli.

3. Gene detection using EHEC-specific DNA probes, the sensitivity and specificity can reach 99%; or PCR analysis of EHEC DNA sequence, found that its hemolysin AB gene is unique to EHEC, its specificity, sensitivity and rapid The results of 3~4h can be found. Other multiplex PCR methods for simultaneous amplification of two pairs of oligonucleotide primers, SLT1 and SLT2, have not been widely used in clinical practice. Genetic testing can be used for clinical research and epidemiological investigation.

It should be differentiated from other Escherichia coli enteritis.

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