Hemolytic E. coli Infection

　　Poultry and livestock are the reservoir and main source of transmission for enterohemorrhagic Escherichia coli infection, such as cattle, sheep, and pigs, with the highest carriage rate in cattle. Patients and asymptomatic carriers are also one of the sources of transmission. Transmission occurs through the digestive tract, through the consumption of contaminated food, water, or contact with patients. Commonly contaminated foods include beef, milk, beef liver, chicken, mutton, vegetables, and fruits. The population is generally susceptible, but the elderly and children are more susceptible. There is a clear seasonal pattern, with July, August, and September being the peak period. The large-scale production, refrigeration, transportation, and supply of fast food are极易 cause large-scale outbreaks of food poisoning; it can also occur sporadically. This disease is globally distributed, and in regions and countries with better sanitation conditions and where most intestinal infectious diseases have been basically controlled, the incidence rate of this disease is rising.

　　Enterohemorrhagic Escherichia coli infection can cause complications such as hemolytic uremia or thrombotic thrombocytopenic purpura. Uremia is a severe renal impairment where metabolic waste cannot be excreted from the body, resulting in the accumulation of a large amount of nitrogenous metabolic products and other toxic substances in the body. This disrupts the acid-base balance and electrolyte metabolism, leading to the destruction of the relative stability of the internal environment of the body, causing autointoxication and producing a complex syndrome. It is often manifested by azotemia, with significantly elevated blood urea nitrogen and creatinine, accompanied by symptoms of the gastrointestinal, nervous muscle, and cardiovascular systems, such as nausea, vomiting, diarrhea, headache, weakness, apathy, insomnia, convulsions, somnolence, and even coma.

　　Thrombotic thrombocytopenic purpura is a rare microvascular thrombosis-hemorrhagic syndrome. More patients are female, aged 20 to 60, without regional or racial differences. The onset is often abrupt, with typical cases showing fever, weakness, and debility. A few patients have a slower onset with prodromal symptoms such as muscle and joint pain, and other symptoms appear rapidly thereafter. There are also cases where pleurisy, Raynaud's phenomenon, and vaginal bleeding in women are the initial complaints.

　　The incubation period for enterohemorrhagic Escherichia coli infection is 1 to 14 days, with 4 to 8 days being common. Prior to the disease, there may be a history of consuming chilled processed fast food. There are three clinical types: asymptomatic infection, mild diarrhea, and hemorrhagic colitis. The typical presentation is an acute onset, diarrhea, initially watery stools, followed by bloody stools. Accompanied by spastic abdominal pain, no fever or low fever, and may be accompanied by nausea, vomiting, and upper respiratory symptoms. Without complications, it can be naturally cured within 7 to 10 days. A few patients may develop acute hemolytic uremic syndrome (HUS) within 1 to 2 weeks of the onset of the disease, manifested as pallor, weakness, hematuria, oliguria, anuria, subcutaneous mucosal hemorrhage, jaundice, coma, convulsions, etc. It is more common in the elderly, children, and those with weakened immune function, with a mortality rate of 10% to 50%. Since the mortality rate of this condition is not low, immediate medical attention should be sought after the appearance of these symptoms in any case, and cannot be ignored to prevent the worsening of the condition.

　　Prevention of enterohemorrhagic Escherichia coli infection.

　　Firstly, just like other intestinal infectious diseases, we should start from everyday life. Firstly, carry out the 'Three Controls and One Elimination' activities, wash vegetables and fruits, do not drink raw water, cook meat thoroughly, heat leftovers thoroughly, and have fly prevention equipment in the kitchen during summer.

　　The second point is to strictly prohibit the mixing of humans and animals, and the domestic animals and poultry in the epidemic area must be kept in pens. Regularly disinfect and kill flies in the pens, and the feces of the livestock and poultry must be treated as harmless before fertilization.

　　The third point is to disinfect the utensils used by the patients, and to disinfect the toilets and compost piles in the epidemic area. The fourth point is to treat the contaminated domestic water supply system. Take disinfection measures. Strictly follow the disinfection procedures, investigate the causes of contamination, and make timely corrections. Conduct pathogen examination of stool specimens for relevant personnel.

　　The last point is to handle contaminated commercially sold meat and meat processing and sales sites. Immediately stop sales and seal up the unsold products, investigate wholesale and sales records. Strictly disinfect and sanitize the processing and production process, and disinfect the processing and production sites, animal feces, and waste. For those who have close contact with the staff, in addition to stool specimen pathogen examination when they are transferred from their positions, they should also be given early preventive medication. The focus of preventing enterohemorrhagic Escherichia coli infection should be to strengthen the management of frozen fast food, prevent food contamination, and heat food thoroughly before consumption.

　　There are three methods for the laboratory identification of enterohemorrhagic Escherichia coli infection.

　　The first method is bacterial culture isolation, increasing the positive rate of stool culture can improve the diagnosis rate. Factors affecting the culture include the characteristics of the stool, the course of the disease, and the choice of culture medium. Bloody stools and those with a short course have a high positive rate; watery stools and those with a long course, especially those over 7 days, have a low positive rate. Sorbitol-MacConkey agar (SMAC) can improve the positive rate.

　　The second method is immunological detection, using monoclonal antibodies for direct ELISA to detect O157:H7 Escherichia coli.

　　The third method is gene detection, using EHEC-specific DNA probes, which have a sensitivity and specificity of up to 99%; or using PCR to analyze the EHEC DNA sequence, finding that the hemolysin AB gene is unique to EHEC, with strong specificity and rapid sensitivity, results can be obtained within 3 to 4 hours. There are also multiple PCR methods that simultaneously amplify the two pairs of oligonucleotide primers SLT1 and SLT2, but they have not been widely used in clinical practice. In summary, through routine laboratory tests, it is possible to accurately determine whether or not a patient is infected with enterohemorrhagic Escherichia coli.

　　The toxin produced by hemorrhagic Escherichia coli is called Shigatoxin or Shiga-like toxin, and the symptoms it causes mainly include abdominal colic, diarrhea, fever, and vomiting, which can develop into hematochezia. Its harm lies in its ability to cause hemorrhagic colitis, hemolytic uremic syndrome, and thrombocytopenic purpura.

　　Hemorrhagic Escherichia coli is more favored by children. Patients should pay attention to dietary health and avoid eating meat porridge after diarrhea and drink some light salt water. When the amount of vomiting is large, patients often experience symptoms such as weakness and dry mouth due to excessive loss of body fluids, and need to be rehydrated promptly. Rehydration can be carried out by oral or intravenous injection. If the degree of diarrhea is moderate, it is best to drink some light salt water. Light salt water is difficult to drink, and if children are unwilling to drink it, some sugar can be added to improve the taste.

　　After diarrhea, the body feels weak and the appetite is poor. What should one eat? Now some chubby children love meat, and parents are afraid that their children will not eat and cannot recover their strength, so they cook porridge with meat for their children. 'Meat porridge will also increase the burden on the gastrointestinal tract.' After abdominal pain and defecation, although the pain is relieved, at this time, the gastrointestinal tract appears edema to varying degrees due to inflammation. If one eats meat dishes, it will worsen the condition. Therefore, in the first two to three days after diarrhea, the diet should be light, and one can drink some plain rice porridge with a little salt.

　　When considering the treatment of hemorrhagic Escherichia coli infection from a Western medical perspective, the first thing that comes to mind is antimicrobial drugs. Whether to use antimicrobial drugs for hemorrhagic Escherichia coli infection is still controversial in academia. Some scholars propose that antimicrobial drugs cannot shorten the course of the disease, cannot reduce the occurrence of complications, and may even promote the release of Veto toxins, leading to the occurrence of HUS. Therefore, it is proposed to avoid the use of antibiotics. However, some scholars also propose that it can be treated similarly to other infectious diarrhea. Severe cases should use antibiotics such as ciprofloxacin (sparfloxacin), berberine, etc.; mild cases can use intestinal mucosal protectants such as octasilicate montmorillonite or microecological regulators. At the same time, attention should be paid to correct dehydration and strengthen supportive therapy. Cases with HUS should be treated according to HUS rescue.