Enterotoxic Escherichia coli infection

　　I. Etiology

　　ETEC settles on the surface of the small intestine without damaging or infiltrating the intestinal mucosal epithelial cells, causing secretory diarrhea by producing enterotoxins. Common serotypes include more than 10, such as O6, O8, O15, O25, O27, O42, O63, O87, O148, O159, etc.

　　II. Pathogenesis

　　There are two types of enterotoxins: heat-labile enterotoxin (LT) and heat-stable enterotoxin (ST). A strain of Escherichia coli can produce both LT and ST, or only one of them. LT is a protein composed of one A subunit and five B subunits, with a molecular weight of 85000, which can be inactivated at 60℃ for 10 minutes. Its antigenicity and toxicity are similar to those of cholera toxin, and the mechanism of causing diarrhea is also the same as that of cholera toxin, which stimulates the increase of cyclic adenosine monophosphate (cAMP) in cells, causing the small intestine to secrete excessively and diarrhea. ST is a low molecular weight (5000) polypeptide haptene, which still retains its activity at 100℃ for 30 minutes. There are two subtypes, STa and STb, which bind to the ganglioside receptors on the membrane of intestinal epithelial cells, stimulate the increase of cyclic guanosine monophosphate (cGMP) in cells, causing the small intestine to secrete excessively in a short period of time and causing diarrhea. The secretory fluid caused by LT and ST is the same, approximately isotonic, with bicarbonate concentration about twice that of plasma and potassium ions 5-6 times that of plasma.

　　1. Dehydration

　　Refers to a symptom caused by the body's consumption of a large amount of water and inability to replenish it in time, causing metabolic disorders. In severe cases, it can cause collapse and even be life-threatening, requiring fluid replacement through intravenous infusion. A group of clinical symptoms caused by the decrease of extracellular fluid, which is divided into hyponatremic dehydration, i.e., the decrease of extracellular fluid combined with low blood sodium; hypertonic dehydration, i.e., the decrease of extracellular fluid combined with high blood sodium; isotonic dehydration, i.e., the decrease of extracellular fluid while blood sodium is normal.

　　2. Acidosis

　　In pathological conditions, when [BHCO3] in the body decreases or [H2CO3] increases, the ratio of [BHCO3]/[H2CO3] can decrease, causing the pH value of the blood to decrease, which is called acidosis. The accumulation of acidic substances in the blood and tissues is characterized by the increase of hydrogen ion concentration in the blood and the decrease of pH value.

　　Acidosis refers to the accumulation of acidic substances in the blood and tissues of patients with acidosis, which is essentially the increase of hydrogen ion concentration in the blood and the decrease of pH value.

　　1. Incubation period:Generally 0.5-7 days.

　　2. Symptoms:Manifested as secretory diarrhea, watery stools, accompanied by abdominal cramps, nausea, vomiting, chills, headache, myalgia, rarely fever, course of disease 4-7 days, the severity of the disease varies, can only have slight diarrhea, can also present with severe cholera-like symptoms, severe dehydration, acidosis, and even death. Adults commonly infected with strains producing ST and LT, children are more commonly infected with strains producing only ST, so adult diarrhea is more severe and lasts longer. 302 Hospital admitted a case of adult ETEC enteritis patient, up to 9000ml of watery stools per day, the course of the disease lasted 38 days.

　　1. Prevent cross-infection in hospitals.

　　2. Use doxycycline for treatment, which can shorten the shedding time.

　　3. Pay attention to diet in daily life, do not eat cold and raw foods, and do not eat too many spicy foods. The main methods are diet therapy, physical exercise, psychological treatment, or the use of some symptomatic treatment drugs. Diet therapy emphasizes regular eating, avoiding spicy and stimulating foods, reducing alcohol, coffee, cold drinks, and not eating foods that can cause diarrhea, such as milk, beans, and cold foods.

　　At the time of diagnosis, in addition to relying on clinical manifestations, auxiliary examinations are also needed. The diagnosis of this disease must involve the cultivation of Escherichia coli in feces and the detection of ST, LT positive. It should be highly emphasized by clinical doctors and patients.

　　What kind of food is good for the body in the case of enterotoxic Escherichia coli infection: It is advisable to have light, clean food and a reasonable diet. The patient's diet should be light and easy to digest, with an emphasis on eating more vegetables and fruits, and a reasonable diet. Pay attention to sufficient nutrition. In addition, patients should also avoid spicy, greasy, and cold foods.

　　1. Treatment

　　The disease has a self-limiting tendency. Mild cases may not require antibiotic treatment, and severe cases may shorten the shedding time after antibiotic treatment. The main drugs used are sparfloxacin (sparfloxacin) or norfloxacin combined with octahedral montmorillonite or berberine. The dosage is the same as that for EPEC treatment. The focus of treatment is to correct dehydration, acidosis, and hypokalemia. Mild cases can use ORS solution, while severe cases may require intravenous fluid replacement, preferably '5:4:1' solution, which means adding 5g of sodium chloride, 4g of sodium bicarbonate, and 1g of potassium chloride per 1000ml of fluid.

　　2. Prognosis

　　ETEC enteritis has a good prognosis, severe cases may have symptoms similar to cholera, with moderate to severe dehydration, acidosis, and even death.