What is Mucor or Mucormycosis? - Black Fungus

Black Fungus (Mucor or Mucormycosis) Fungal Disease

Mucormycosis is also called black mold, black fungus and mucor longum. Mucormycosis is a large genus of fungi in the Mucoridae family of the zygomycete class Mucor. It reproduces with cyst spores and conjugative spores.

Mucormycosis exists in the environment such as soil, manure, grass and air. It grows well under conditions of high temperature, high humidity and poor ventilation.

The Asian name is Mucor and the western name is Mucormycosis, also known as black mold and Mucor longum. 

The reproduction method uses cyst spores and zygospores to multiply. 

The growth environment is high temperature, high humidity and poor ventilation. It belongs to saprophytic fungi.

 

Table of Contents

1. Introduction

2. Biological traits

3. Mucor infection

4. appearance characteristics

5. Pathogenicity and immunity

6. Distribution and use

7. Microbiological examination

8. Cause disease

▪ Disease test

▪ Drug contamination

▪ Pulmonary Mucormycosis

9. Principles of Control


Introduction 

Mucor and Zygomycota are widely distributed in nature. They are saprophytic fungi with strong ability to decompose proteins and often cause food mildew. It is a conditional pathogenic fungus, which causes disease in the human body only when the body's immunity is low and extremely weak.

 

Biological Traits of Mucormycosis

Mucor is a multicellular fungus, the hypha is not separated, the branches are at right angles, sporangia stalks grow on the mycelium, and spherical sporangia are formed at the top, which contains a large number of sporangia spores.

On the SDA medium, it grows rapidly at 25°C or 37°C, forming white filamentous colonies, and the colonies become gray-brown after spore formation. Mucor has both asexual reproduction and sexual reproduction.

Mucor infectionedit

The drug treatment of mucor infection should be amphotericin B. If the central nervous system or sinuses are involved, surgical intervention can be considered to reduce the mortality rate.

Fungal Disease of Mucormycosis


What are the Shape features of Mucormycosis?

The hyphae are not septal, multinucleated, branched, and can spread widely inside and outside the substrate, without false roots or creeping hyphae. Does not produce solid colonies. 

Single, raceme-shaped or pseudo-axially branched cyst stems are directly produced on the mycelium. 

There is a spherical sporangia at the top of each branch, and there are cysts of different shapes inside, but no sac holder.

A large number of spherical, oval, thin-walled, smooth cyst spores are produced in the cyst. 

After the spores mature, the sporangia burst and release the spores. Sexual reproduction uses heterogeneous or homologous coordination to form a conjugative spore. Certain species produce chlamydospores.

The mucor mycelium is white at the beginning, and then grayish-white to black, which indicates that the sporangia are mature in large numbers. 

Mucor mycelium can extend about 3 cm per day, and the production speed is significantly higher than that of shiitake mushroom mycelium.


Mucormycosis Pathogenicity and immunity

In patients with weakened immunity, mucor infection first occurs in the nose and ears. Mucor enters through the nasal cavity and respiratory tract, and can invade the maxillary sinus and orbit, causing necrotizing inflammation and granuloma.

It can also invade the human brain through the bloodstream. Cause meningitis.

It can also spread to the lungs, gastrointestinal tract, etc. The disease has a rapid onset, rapid progress, difficult diagnosis, and high mortality.


Distribution and usage

Mucor has a wide range of uses. It often appears in alcoholic medicine. It can saccharify starch and produce a small amount of ethanol, produce protease, and has the ability to decompose soybean protein. It is mostly used to make fermented bean curd and tempeh in our country. 

Image showing Mucormycosis infection


Many Mucor molds can produce oxalic acid, lactic acid, succinic acid and glycerol, and some Mucor can produce lipase, pectinase, rennet and so on. Commonly used Mucor mainly includes Mucor rouxii and Mucor racemosus. Saprophytic, widely distributed in distiller's yeast, plant residues, decaying organic matter, animal manure and soil. 

There are important industrial applications, such as using its amylase to make koji and wine using its protease to brew fermented bean curd, tempeh, etc. Representative species such as M. racemosus, M. mucedo, M. rouxianus, etc.


What is Microbiology inspection for Mucormycosis?

Take pus, sputum, sinus aspirate or autopsy specimens, digest with 10% KOH, and then microscopically examine. If you see thick hyphae with no septum, strong refractive index, and sporangia, you can preliminarily identify them.


What diseases can Mucormycosis cause?

Diseases caused by Mucormycosis. The main strain is M. corymbifer, which can invade blood vessel walls and cause thrombosis and tissue necrosis. 

It is usually secondary to diabetes or other chronic wasting diseases, and the disease is acute; severe symptoms can be fatal. 

According to clinical manifestations:

1. Cerebral mucormycosis is caused by mucor from the nasal cavity and paranasal sinuses to reach the brain along the small blood vessels, causing thrombosis and necrosis.

2. Pulmonary mucormycosis is mainly manifested as bronchial pneumonia, but also pulmonary infarction and thrombosis.

3. Mucormycosis of the gastrointestinal tract, which is more common in the terminal ileum, cecum and colon, esophagus and stomach can also be involved.


Whats is Mucormycosis Disease Test?

Take the diseased tissue for direct microscopic examination, it can be seen that there is no septal hyphae. Compared with Aspergillus, the hyphae are thicker, have fewer branches, and have not many spores. 

The specimens are inoculated on the colonies grown on Sabol's medium, and they start to be white. 

Gradient gray-black, mycelium can grow spores, with sporangia spores at the end, and sometimes conjugative spores can be seen occasionally. 

Treatment can be amphotericin B, sometimes combined with surgical resection or drainage.


Drug Contamination

In 2009, a number of blood cancer and lymphoma patients in Hong Kong Queen Mary Hospital died of Mucormycosis infection. 

Allopurinol, a drug produced by Eurochem Pharmaceuticals in Hong Kong to treat gout and excessive uric acid, is suspected of being contaminated, and the content of Mucor is 100 times higher than the standard.


Pulmonary Mucormycosis

English name: pulmonary mucormycosis alias mucormycosis, mucormycosis, algae disease, zygomycosis, phycomycosis, zygomycosis, mucormycosis.

Overview: This disease is caused by several possible pathogens of the Mucoridae family. It often invades the blood vessel wall and vascular cavity, and causes inflammation and thrombosis. It is often complicated with diabetes. It is more common in burn patients.


Cause of Mucormycosis

Fungi that can cause pulmonary mucormycosis belong to the subphylum Zygomycota, Mucor, Mucorales, Mucorales, and occasionally from other families of Mucorales, such as Mortierellaceae, Cunninghamiaceae, caused by Kokomyceae, Phalaenopsis, etc. Among them, Rhizopus, Mucor and Absidia are the three most common types of fungi that cause pulmonary mucor.

Among the three types, Rhizopus is the most common type, especially Rhizopus and Rhizopus oryzae.

 

Principles of prevention of Mucormycosis

There are no effective preventive measures and treatment methods. Antifungal drugs such as amphotericin B can be used in the early stage, and the lesion can also be surgically removed.




Clinical case: A case of Pulmonary Mucormycosis

 Credit Authors: Department of Respiratory Medicine, Peking University First Hospital Mou Xiangdong; Wang Guangfa; Zhang Wei

 

 

X Ray chest


 

X-ray chest radiograph shows that the left lung field has decreased brightness, uneven density, and the mediastinum and trachea shifted to the left.

 

CT Scan

Chest CT showed the disappearance of the left main bronchus opening, the left lung consolidation with atelectasis, the left pleural effusion, and the huge round soft tissue in the left lung.

Fiberoptic bronchoscopy


 

Fiberoptic bronchoscopy showed that the left main bronchus was completely blocked by white gelatinous material, and the carina was white ulcers.


 

Clinical Information

A 48-year-old female patient with intermittent fever and hemoptysis style=color:blue> hemoptysis for 6 months, exacerbated with suffocation for 7 days.

 

The patient had a history of type 2 diabetes for 2 years. He developed diabetic ketoacidosis with coma 6 months ago, and developed fever 1 week later. Chest X-ray showed exudative shadow of left upper lung, chest CT showed consolidation of left upper lung with cavity formation. 

The patient did not get better after a variety of broad-spectrum antibiotics, quadruple anti-tuberculosis and itraconazole antifungal therapy and developed hemoptysis.

 

Physical examination: left trachea, left lung percussively, and breath sounds disappeared; abdomen was flat and soft, no tenderness, 4 cm below liver ribs; pitting edema of both lower limbs.

 

Auxiliary inspection:

Peripheral blood leukocytes are 22.7×109/L, neutrophils are 84%, and hemoglobin is 50 g/L.

 

Multiple sputum smears and cultures were negative, and blood cultures were negative for bacteria, fungi, and acid-fast bacilli.

 

The chest radiograph showed a large area of ​​exudate from the left lung (Figure 1). Chest CT showed consolidation of the left lung with atelectasis, pleural effusion on the left, and large round soft tissue shadows in the left lung (Figure 2).

 

Fiberoptic bronchoscopy showed that the left main bronchus was completely blocked by a white gel mass (Figure 3). The smear of bronchial secretions was negative for fungus and culture.

 

The pathology of the tumor showed a large number of hyphae in the necrotic tissue, and its morphology suggested that it was a mucor mycelium (Figure 4).

 

 

 

Diagnosis: pulmonary mucormycosis

Outcome: The patient developed massive hemoptysis (about 3000 ml) on the 7th day of hospitalization, and died after rescue.

 

 Comment

Pulmonary mucormycosis is a severe pulmonary infection caused by some pathogenic fungi in the order Mucorales of the fungal kingdom Zygomycota. It is also called pulmonary zygomycosis (pulmonary zygomycosis). 

The body's immunity is reduced (such as diabetic acidosis, hematological malignancies, and organ transplantation or application of immunosuppressive agents).

 

The most common symptoms of this disease are fever and cough. More than half of patients have hemoptysis, chest pain, and dyspnea. 

Mucor has a strong penetrating power and often erodes pulmonary arterioles, causing pulmonary embolism and pulmonary infarction. If not treated in time, most patients die of massive hemoptysis.

 

 

 

The most common imaging manifestations of this disease are progressive and homogeneous consolidation of lung lobes or lung segments. It can also be manifested as single or multiple pulmonary nodules or masses, more common in the upper lobe. Holes appear in more than 40% of cases. Air half-moon sign is less common than pulmonary aspergillosis. Its appearance suggests a tendency to massive hemoptysis, but the prognosis of the patient is relatively good.

 

It should be noted that the positive rate of culture of sputum, needle aspiration and bronchoalveolar lavage fluid for pulmonary mucormycosis is <5%, and the diagnosis often depends on histopathology. 

The characteristics of the mucor hyphae are: 7-25 μm in diameter, uneven thickness, branching at right angles, wide without separation or few separation, and thin wall.

 

Once the diagnosis is confirmed, intravenous amphotericin B should be administered immediately, and surgical resection of the lesion should be considered for those who have not improved after 2 weeks of treatment. Other commonly used antifungal drugs are ineffective.


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