Zygomycosis

Introduction to zygomycosis Zygomycosis is an acute, subacute and chronic conditional infection caused by the pathogens of the genus Zygomycetes, which is distributed worldwide. In recent years, with the expansion of immunodeficiency population, the incidence of the disease has increased significantly. In China, in 1994, Liao Wanqing first reported Rhizopus arrhizus caused by gangrenous pyoderma. Mucor is ubiquitous in nature and is an important spoilage organism for organic matter. Under normal circumstances, the bacteria are non-virulent, and the infection mostly occurs in patients with severe basic diseases. The pathogenesis of mucormycosis is acute, the progress is fast, the mortality rate is high, and the infection caused by insects is mostly chronic inflammatory or granulomatous disease. The diagnosis is mainly based on mycological examination and histopathological examination. The principle of treatment of mucormycosis includes controlling the basic diseases, removing infected necrotic tissue, and timely intravenous amphotericin B. The treatment of frog fecal infection is effective with saturated potassium iodide solution, 30mg/ Kg, oral ketoconazole 400mg / d, rarely used amphotericin B. basic knowledge The proportion of illness: 0.003% Susceptible people: no special people Mode of infection: non-infectious Complications: zygomycosis

Cause of zygomycosis

Causes:

The zygomycetes are a relatively primitive, fast-growing, widely distributed terrestrial fungus. Most of them are found in plant spoilage and soil. Many are common polluting bacteria in the environment, which can cause food spoilage. It is a pathogenic bacteria of plants and insects, and it can cause human diseases. This kind of fungus sexually propagates to produce spores, asexually propagates to form sporangia spores, hyphae are multinuclear, and most of them have no membrane, making it easy to be The identification of filamentous fungi, the genus Zygomycetes as a class, is considered to be a fairly natural (rather than artificially hard) group, which is composed of chitosan in the cell wall - chitin components and the most recent molecules The biological method confirmed that the zygomycetes include 7 orders and 30 families, but only Mucor and Molds are of medical importance.

Mucor pathogens include Rhizopus, Rhizopus, Rhizopus, Mucor and Capsule, and Syphilis, Saccharomyces, Bottles, Cofidae And various fungi in the genus Mycorrhizal, the pathogens of the genus Mycoplasma include the genus Rana sylvestris in the frog family, and the genus Coronaria and A. sp., among which the Rhizopus oryzae (synonym: less root) Rhizopus) is the most common pathogen, accounting for 60% of culture-positive cases and 90% of cases of nasal brain infection. Rhizopus oryzae is distributed worldwide, mostly in tropical and subtropical regions, from soil, spoiled vegetables, food, Animals and bird droppings are separated. In Indonesia, China and Japan, Rhizopus oryzae is commonly used in pickled foods and alcoholic beverages to produce an ergot alkaloid, ergot, which is toxic to humans and animals.

Mucor is ubiquitous in nature and is an important spoilage organism of organic matter. Under normal circumstances, the bacteria are non-virulent. The infection usually occurs in patients with severe basic diseases. The optimal growth temperature of the pathogen of the mucormycosis is 28-30. °C, can also grow at 37 °C during separation. Mucor is characterized by coarser hyphae, no separation or very little separation; mycelium wall is thicker, side branches and mother branches are at right angles; good invasion of blood vessels, easy to form thrombus in the cavity It causes local tissue necrosis. The pathogen of entomopathogenic fungi is prevalent in decaying plants and many gastrointestinal tracts of crawling and amphibians, but it is not pathogenic to animals. The bacteria have not been isolated from insects, but spores can sometimes be attached to insects. It has become a medium of transmission. The bacteria are not cold-tolerant, and the cold environment is very fast. The bacteria can be isolated in the environment of tropical and subtropical regions. The bacteria grow well at 25-37 °C, but the room temperature grows poorly.

Pathogenesis:

Mucor is ubiquitous in nature and is an important spoilage organism of organic matter. Under normal circumstances, the bacteria are non-virulent. The infection usually occurs in patients with severe basic diseases. The optimal growth temperature of the pathogen of the mucormycosis is 28-30. °C, can also grow at 37 °C during separation. Mucor is characterized by coarser hyphae, no separation or very little separation; mycelium wall is thicker, side branches and mother branches are at right angles; good invasion of blood vessels, easy to form thrombus in the cavity , causing local tissue necrosis.

Zygomycosis prevention

Primary prevention

(1) Separate susceptible patients with filtered air or laminar air to prevent cross-infection in hospitals.

(2) Control of diabetes, lymphoma and leukemia patients, strict control of immunosuppressive agents, cytotoxic drugs, anticancer agents, etc., have a certain preventive effect.

(3) Strengthen food management and prevent fungal pollution.

2. Secondary prevention

Because the disease is very urgent and serious, early diagnosis is extremely important. Because mucormycosis is often difficult to detect in secretions, and it is difficult to identify, early diagnosis mainly depends on clinical evidence: that is, the disease is urgent, the condition is fierce, and the first part of the disease is the nasal brain. Following the chest, abdomen, pelvis, stomach and skin, pathogenic factors include acidosis of diabetes, leukemia and lymphoma of lung infection, malnutrition of intestinal infection, such as protein deficiency in children, combined with clinical manifestations, experiments Room (including fungal culture) and pathological examination (secretion, extracts, scraping, etc.) may achieve rapid diagnosis. Once diagnosed, amphotericin B should be used immediately, and 1.2 mg/kg should be administered every other day. Immediate control, surgical debridement in the nasal cavity, there are also advocated combination therapy, in addition to amphotericin B, plus 5-Fc, itraconazole or fluconazole.

3. Three levels of prevention

Timely use of amphotericin B can reduce the mortality rate of this disease from 80% to 90% to about 50%, control diabetes, nasal necrotic tissue for surgical debridement, can improve the prognosis of this disease.

Complications of zygomycosis Complications

Nasal encephalopathy, pulmonary zygomycosis, digestive tract bacillary disease, cutaneous zygomycosis, neonatal zygosis and others.

Symptoms of zygomycosis common symptoms chest pain abdominal pain abdominal distension papule severe burn intracranial hypertension nausea pustule hemoptysis dyspnea

1. Mucormyc infection: Mucormycosis infection is rapid, rapid progress, high mortality, clinical features are rapid fever, tissue necrosis, different clinical types are often related to the patient's underlying disease, the prognosis and basis of the disease Disease, type of infection and whether it is diagnosed and treated early, more common in diabetes, hunger, severe burns, intravenous drugs and other diseases such as leukemia, lymphoma, immunosuppressive therapy using cytotoxic drugs or corticosteroids, use Treatment with ferric amine (an iron chelating agent for the treatment of excessive iron) and severe trauma, the incidence of co-infection in HIV-positive patients is gradually increasing.

(1) Nasal encephalobacteria: pathogens including Rhizopus oryzae (the most common), Absidia, Brassica, Brassica, Trichoderma, and Mucor, early and chronic Similar to rhinitis, such as nasal congestion, headache, etc., then, the nasal cavity can flow out of dark red blood secretions, nasal cavity, sinus can form necrotizing granuloma, invading the eye can cause eyelid edema, eye muscle paralysis, eyeball protrusion, pupil fixation, vision Decline and even blindness, once invaded into the brain, there may be rapid symptoms such as meningitis and encephalitis. The cranial nerves are often involved, especially the V and VII cranial nerve dysfunction. There may be facial pain, paralysis and other symptoms. As the disease progresses, the pathogen Invasion of larger cerebrovascular vessels, causing embolism and necrosis, advanced patients may have intracranial hypertension and cerebral palsy, most leading to death.

(2) Pulmonary zygomycosis: pathogens include Rhizopus oryzae (most common), Absidia, Brassica chinensis, Rhizopus oryzae, R. schipperae, indicating Mucor, Due to the invasion of the pathogens into the lungs through the respiratory tract, a small number of secondary respiratory secretions due to inhalation of nasal secretions, common persistent fever and rapid progressive pulmonary infiltration, mostly manifested as non-specific bronchial pneumonia, when invading the pulmonary artery to produce thrombosis and necrosis, appears Chest pain, hemoptysis and massive hemoptysis, X-ray signs of lungs are different, can be nodular, hollow, most small patches, can also be general pneumonia-like changes, with pleural reaction, pleural effusion, etc. At the same time, combined with other organs, Mucor infection, so the disease course is short, rapid development, the mortality rate is as high as 80% to 90%.

(3) Digestive tract zygomycosis: pathogens include Absidia pallidum (most common), Rhizopus oryzae, R. aygosporus, Rhizopus genus Rhizopus, indicating Mucor, lesions The stomach and duodenum are the most, accounting for more than 95% of the type. Chronic digestive ulcer is an important underlying disease. The ratio of male to female is 10:1, aged 21 to 70 years, and the course of disease is 4 months to 30 years. Symptoms are upper abdominal pain, may be associated with nausea, vomiting and other symptoms, secondary to ulcers, the abdominal pain regularity, degree, frequency have changed, according to the ulcer treatment effect is not good, gastroscopic examination shows huge ulcer diameter between 3 ~ 5cm The surface is covered with thick layers of soil moss, and the barium meal shows huge ulcers and shadows. The gastric peristalsis is poor, and it is very difficult to distinguish from gastric cancer. Therefore, the preoperative diagnosis rate of gastric mucormycosis is very low.

(4) Skin zygomycosis: pathogens include Rhizopus arrhizus roots, Rhizopus oryzae, Rhizopus genus (the most common), Absidia, Brassica chinensis, Artemisia scoparia, Arthritis Bottle mold, microspore of Microsporum, Microsporidia, spores, Mucor, Rhizopus, Raman and Raflates, the primary infection is often caused by trauma, surgery, etc. There are various forms of damage, including erythema, papules, plaques, pustules, ulcers, necrosis, etc. The course of disease is 2 months to 24 years. Generally, the blood is not disseminated, the prognosis is good, and the secondary infections are mostly from the nose, brain and lungs. Or other parts of the spread of mucor, the skin lesions began to be painful or painless erythema, nodules, gradually enlarged, after the central ulcer, eschar and dry necrosis, the surrounding is grayish white, the most peripheral is edematous erythema, and gradually Outward expansion, short course of disease, poor prognosis.

(5) neonatal zygomycosis: depending on the location of the infection, invasion of the intestine may have vomiting, abdominal distension, bloody stools, etc. If the brain, lungs, liver, etc. are invaded, there is poor response, difficulty in breathing, jaundice and other corresponding parts are non-specific Symptoms, liver necrosis caused by umbilical wounds is a characteristic of neonatal infection, because it is often involved in multiple organs, clinically no specific symptoms, difficult to distinguish from other serious infectious diseases, and the mortality rate is extremely high.

(6) Others: Mucor may also invade the kidneys and uterus.

2. Infection caused by insects: mostly chronic inflammatory or granulomatous diseases.

The frog fever fecal infection is usually confined to the lower limbs, the subcutaneous tissue of the chest, back or hip, mainly found in male children, and begins to damage the subcutaneous nodules, which then enlarge, harden, harden, and painless swelling, which can be involved in the affected muscles. Free to move but attached to the skin, no ulcers but pigmentation, systemic damage is rare, including ulceration caused by hard palate penetration, gastrointestinal and muscle infections.

Otomegaly infection is mainly confined to the submucosal layer, characterized by polyps or obvious palpable localized granulomas, which are more common in adult males (80% of cases). The infection usually begins on the unilateral side of the nasal mucosa. Symptoms include nasal congestion and more secretions. Pain in the sinus area, subcutaneous nodules in the nasal or nasal area can cause extensive facial swelling, and the clinical subtypes that have been described include lung and systemic infections.

Early diagnosis of infection is the key to successful treatment. Only the clinical features of nasal infection are significant. Therefore, the diagnosis is mainly based on mycological examination and histopathological examination. This kind of bacteria is a common saprophytic bacteria, if it is from necrotic tissue, sputum or bronchoalveolar lavage fluid. Muscle isolation in culture should be carefully considered, but if the patient is diabetic or immunosuppressed, culture positive is important for diagnosis.

Examination of zygomycosis

Mycological examination.

1. Direct microscopic examination: large in the clinical specimens, 10 ~ 15m wide, most of the non-diaphragm, thin-walled hyphae, often focal root expansion and irregular branches, scraping, sputum and points By staining (calcofluor), direct microscopic examination from the clinical specimens of necrotic tissue, sputum or bronchoalveolar lavage fluid found that Mucor was more meaningful than culture, and the bacteria were easily distinguished from other fungi such as Aspergillus.

2. Fungal culture: Mucor has no special requirement for nutrition. It can be grown on conventional fungal medium without cycloheximide. The primary isolation medium should contain chloramphenicol or gentamicin. As a carbon source, ammonium or peptone is used as a nitrogen source. Generally, the antibiotic-containing sand castle agar is used as the primary separation medium, and potato agar is used as a strain for preservation and identification. Thiamine is the only growth factor required for some strains. For example, the genus Ophiopogons, most of the mucormycetes are abundant and grow rapidly. The whole medium can be filled in a few days and the lid can be pushed open. However, some strains such as the sarcophagus and the vascular tube Mildew identification is relatively difficult, because most of the primary separation can not be sporulated and need to pass to potato dextrose agar, sporulation can be stimulated in auxotrophic medium, such as corn flour glucose sucrose yeast extract agar.

The colony of the fungus on the sand castle agar is yellow to gray, with limited edges, thin appearance, waxy luster, radial ridges on the surface, and the spores are typical for about 10 days in culture. The wall is smooth and can be seen by the spores. The tortoise-like structure composed of hyphae shows that there are many thick-walled spores of 20 to 40 m in size during the culture, and the secondary spores are directly produced by molecular spores on the conidiophores.

Histopathology: The histopathology of Mucor infection has no obvious specificity, often edema and neutrophil infiltration, rare strong inflammatory reaction, because the patient's immunity is low, visible wide, ribbon-like hyphae, diameter 7 ~ 15m, right angle bifurcation, diagnostic value, no separation or very little hyphae, sometimes because the wall is thin, hyphae can be twisted and folded, there seems to be many compartments, sometimes hyphae is not wide, but there are still right angle branches Even thick-walled spores are seen, and blood vessels are often invaded by hyphae, leading to necrosis of adjacent tissues. Other histopathological changes include necrosis with acute and chronic infiltration, and involving blood vessels. Infiltration of blood vessels often leads to thrombosis, obstruction and vascular necrosis, sometimes Spore cysts of well-defined small columns in the sporangia can be seen in well-ventilated nasal and lung tissues.

In recent years, CT, magnetic resonance, fine needle aspiration and other techniques have been applied to the diagnosis of systemic or nasal-type hairy mold infection, and indirect enzyme-linked adsorption test for pathogen detection, but still need to accumulate experience.

Diagnosis and identification of zygomycosis

Early diagnosis of infection is the key to successful treatment. Only the clinical features of nasal brain infection are significant, so the diagnosis is mainly based on mycological examination and histopathological examination. This kind of bacteria is a common saprophytic bacteria. If the mucormycosis is isolated from necrotic tissue, sputum or bronchoalveolar lavage fluid, it should be carefully considered. However, if the patient is a diabetic or immunosuppressed patient, positive culture is important for the diagnosis.

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