Amoebic infection in the tissue

　　Whether the small trophozoite can invade the tissue and cause lesions is determined by multiple factors, among which the main ones are:

　　1. Changes in the host's physiological function, such as malnutrition, infection, intestinal dysfunction, and intestinal mucosal injury, lead to a decrease in the host's resistance;

　　2. Under the synergistic action of suitable bacterial species (bacteria can provide suitable physical and chemical conditions for the growth and reproduction of amoebas), it promotes the proliferation of amoebas. In addition, it can also directly damage the host's intestinal mucosa, which is conducive to the invasion of amoebas and enhances their pathogenicity, etc.

　　Amoebas can infect the liver via the mesenteric veins, but the possibility is extremely low. If a liver abscess has already occurred, the abscess can rupture and penetrate the diaphragm to infect the right pleural cavity. Chest X-rays and puncture secretion examination for amoebic trophozoites can confirm the diagnosis. Intestinal amoebas can also enter the perianal, vaginal, and urethral areas, causing abscesses or inflammation in the corresponding regions. Common complications include enteritis, amoebic abscess, and amoebic appendicitis, etc.

　　The clinical manifestations of amebiasis are varied, often with a persistent phenomenon, that is, the course of the disease is prolonged, and the symptoms are intermittent. According to the clinical classification suggested by WHO, it can be divided into asymptomatic cystic infection and symptomatic invasive infection. The former accounts for more than 90%, most of which are infections by non-invasive species in the complex, and the latter is divided into intestinal amebiasis (including amebic dysentery, enteritis, ameboma, amebic appendicitis, etc.) and extraintestinal amebiasis (including amebic liver, lung, brain abscess, and cutaneous amebiasis, etc.). The typical amebic dysentery is often accompanied by abdominal colic and tenesmus, and the acute abdominal type of dysentery with purulent glucose feces is not common.

　　Mostly manifested as subacute or chronic persistent enteritis, with symptoms such as abdominal distension, weight loss, anemia, etc. Extraintestinal amebiasis is most common with amebic liver abscess, which is hematogenous dissemination, commonly occurring in the right lobe of the liver, often accompanied by a history of intestinal amebiasis, mostly with a slow onset, remittent fever, liver enlargement, pain in the liver area, progressive weight loss, anemia, and nutritional edema, etc. Amebic lung abscess is less common, with hepatogenic and enterogenic origins, the former mostly caused by the direct penetration of amebic liver abscess; the latter spreads through the blood vessels, the focus is not limited to the lower lobe, and in extremely rare cases, liver abscess can penetrate into the pericardium, penetrate the abdominal wall, and intestinal amebiasis can also enter the perianal, vagina, urethra, and other sites to cause abscesses or inflammation in the corresponding areas, common complications include enteritis, ameboma, amebic appendicitis, etc.

　　Amebic colitis mainly occurs when amebae contaminate water, food, vegetables, and other things, entering the human intestinal tract and causing the disease. The disease is prone to recurrence and the symptoms vary in severity, so chronic diarrhea or unclear intestinal diseases should consider the possibility of this disease. The disease is prone to complications such as intestinal hemorrhage, intestinal perforation, appendicitis, colitis, liver abscess, and other intestinal and extraintestinal complications, which should be vigilant. For patients with recurrent chronic diarrhea, the effect of applying simple antibiotics is poor, and adding anti-amebic drugs often produces unexpected effects. Paying attention to food and drinking water hygiene, forming good personal habits, eliminating pests, and maintaining a good living environment are all effective measures for preventing infection.

　　1. Investigate and treat patients and carriers to control the source of infection, especially to find and treat carriers and chronic patients engaged in food work, and to identify the species of worms and determine the treatment strategy when necessary.

　　2. Managing feces and protecting water sources are the main links in cutting off the transmission route of amebiasis. Localized measures should be taken to treat feces in a harmless way, kill the cysts, and strictly prevent feces from contaminating water sources, which should be the key measures to prevent and control amebiasis.

　　3. Pay attention to the hygiene of food and drinking water, develop good personal habits, eliminate pests, improve the environment, and prevent diseases from entering the mouth, which are powerful measures to protect susceptible populations.

　　First, pathogen examination

　　1. Feces examination

　　(1) Saline smear method

　　Applicable to purulent blood stools or watery stools with amebic enteritis in acute dysentery patients, mainly to check the active trophozoites, but the specimens must be fresh, and the faster the delivery for inspection, the better. It is not suitable to be placed at 4℃ for more than 4-5 hours. The typical amebic dysentery feces is a sauce-like red mucus with a foul smell. Under the microscope, it can be seen that the mucus contains many clumped red blood cells and fewer white blood cells, and sometimes there are rhombic crystals (Charcot-Leyden crystals) and active trophozoites. These characteristics can distinguish the feces from bacterial dysentery.

　　(2) Cyst Concentration Method

　　For the formed feces of chronic patients, the direct smear method can also be used to find the cyst stage, which is often stained with iodine solution to show the nucleus of the cell, facilitating differential diagnosis. However, cyst examination can be improved by concentration methods, and common methods include the zinc sulfate floatation concentration method and the mercury iodine formalin centrifugal precipitation method.

　　Atypical chronic amebiasis, which is common in clinical practice, is often not easy to find the etiological agent in the feces. According to analysis, the detection rate of asymptomatic patients or those with lesions limited to the cecum and ascending colon in routine wet smears or fixed staining smears does not exceed 30%. The positive rate can be increased to 60-80% with three consecutive tests one day apart, and can reach above 90% with five tests.

　　2. Artificial Culture

　　There are many improved culture media available for selection. The diagnostic routine for isolating and culturing worms from fecal specimens generally uses sterile culture, but the detection rate is usually not high in most subacute or chronic cases, so the culture method seems not suitable for routine examination. The cultivation of symbionts requires special culture media and technical requirements and is suitable for research.

　　3. Tissue Examination

　　The detection rate is highest when using sigmoidoscopy or colonoscopy to directly observe mucosal ulcers and perform biopsies or smears of scraping materials, about 85% of dysentery patients can be detected using this method. Live specimens must be taken from the edge of the ulcer, and abscess puncture should also be taken from the wall, and attention should be paid to the characteristics of the pus.

　　Attention should be paid to the cleanliness of the containers and the effects of medication and treatment measures on the patient during the etiological examination. Certain antibiotics, anthelmintic drugs, laxatives, astringents, high and low osmotic enemas, barium meal, and self-urine contamination can all cause trophozoites to die and interfere with the detection of pathogens.

　　Immunological Diagnosis

　　Due to the ease of missed or misdiagnosis of the etiological agents of amebiasis, immunological diagnosis, although an indirect auxiliary diagnostic method, has great practical value. Since the establishment of the cultivation of amebic symbionts and the emergence of specific monoclonal antibodies in the 1960s, pure antigens of intracellular amoebae and high-quality tool antibodies have been provided. Various immunodiagnostic methods have been developed abroad, and in recent years, various modified methods of enzyme-linked immunosorbent assay (ELISA) have been widely used. Generally, the detection rate of specific cyclic antibodies in patients with liver abscesses can reach 95% to 100%, in patients with invasive colitis 85% to 95%, and in asymptomatic carriers only 10% to 40%. The titer may vary depending on the condition, but larger abscesses are usually associated with higher titers. Therefore, serological diagnosis has great auxiliary diagnostic value for patients with acute onset. In serological epidemiological surveys, the changes in the level of population antibody titers can indicate the incidence situation in the region. The application of monoclonal antibodies and DNA probe hybridization technology provides a specific, sensitive, and anti-interference tracing tool for detecting pathogenic substances in host blood and excreta. The application of monoclonal antibodies to detect worm antigens in feces and the use of DNA probes to identify worm species in feces have been reported.

　　In addition to conventional treatment, attention should also be paid to the following aspects in diet for invasive amebiasis: patients should pay attention to light diet, stay away from spicy and stimulating foods, and follow medical advice when necessary.

　　1. Investigate and treat patients and carriers to control the source of infection, especially to find and treat carriers and chronic patients engaged in food work, and to identify the species of worms and determine the treatment strategy when necessary.

　　2. Managing feces and protecting water sources are the main links in cutting off the transmission route of amebiasis. Localized measures should be taken to treat feces in a harmless way, kill the cysts, and strictly prevent feces from contaminating water sources, which should be the key measures to prevent and control amebiasis.

　　3. Pay attention to the hygiene of food and drinking water, develop good personal habits, eliminate pests, improve the environment, and prevent diseases from entering the mouth, which are powerful measures to protect susceptible populations.

　　4. Antihelminthic treatment currently uses metronidazole (metronidazole) as the first-line drug for acute amebiasis (including abscesses in different locations), which has good oral absorption, few side effects, but low concentration in the colon, and is not ideal for treating carriers alone. To cure intestinal amebiasis, it should be combined with quininic drugs such as chiniofon, viomycin, etc., which are effective against intestinal amebae. Chloroquine is also an effective drug for treating extraintestinal amebiasis. Traditional Chinese medicine such as Brucea javanica seeds, allicin, and Pulsatilla chinensis also have certain efficacy and few side effects.