Fungal culture test

This is an automatically translated article.

The article is professionally consulted by Master, Doctor Tran Thi Vuong - Doctor of Microbiology - Laboratory Department - Vinmec Hai Phong International General Hospital

1. When to test for fungal cultures?

Most fungi cause disease when the body has favorable conditions such as using a lot of antibiotics, using corticosteroids for a long time, disrupting the microbial balance leading to fungus growth or when the body is impaired. immunological methods such as HIV/AIDS, organ transplantation, use of immunosuppressive drugs...
For the method of scouring the fungus from the specimen, it only tells us whether there is a fungus or not. Fungal culture method shows that, when culturing on some suitable medium for the fungus to grow into colonies, then based on the macroscopic and microscopic characteristics of the colony to determine the species or in some cases must Based on the biochemical properties of each new species of fungi.
Test for fungal culture is indicated in patients with factors such as:
The patient has suspected fungal lesions on the internal organs, skin, hair, nails... The patient must lie down. Long-term hospital use, ventilator, catheter, urinary catheter .... Suspicious signs in high-risk subjects such as immunodeficiency, chronic disease, cancer .... Patient has fever. prolongation of unknown cause. When you see some suspicious signs such as: itchy skin, prolonged itchy head, white patches in the mouth, itching or vaginal discharge ...

2. Procedure for testing fungal culture

Currently, the process of performing a cultured fungal test is carried out according to the following steps:
Step 1: Take samples, depending on the location of the disease, the specimen will be different.
Step 2: Cultivate the fungus on Sabouraud's medium, incubated at 30°C.
If the specimen is skin, hair or nail: Cut the culture into 6 to 8 spots on the Sabouraud plate. If the specimen is mucinous: Aspirate 3-5 drops of fluid, then inoculate on Sabouraud plate. If the specimen is urine: A quantitative culture technique should be used. Step 3: Look for fresh mushrooms. When enough time to culture, conduct microscopic assessment of colony morphology, colony form
Step 4: Determine the results by observing the structure, properties, and color of the colonies.
In case of not seeing results after 4 days: negative. In case of positive, it is necessary to determine the type of fungus.
Characteristics of colonies and on microscopy of some yeasts:
Candida colonies are smooth, smooth, creamy in color and usually grow rapidly after 24 hours. On microscopy, yeast cells are round or oval, with or without budding. Smooth beige Cryptococcus colonies are usually drier than Candida and grow slowly usually after 48 hours. On microscopy, fungal cells are usually round, large in size. Characteristics of mycelium colonies: For Aspergillus fungi, the color of colonies varies depending on the species. The fungus P. marneffei, which produces a red pigment, diffuses into the medium when cultured at room temperature. After culture the fungal culture plates were discarded after 7 days of culture.

3. Meaning of culture fungal testing

Fungal testing is important in clinical practice:
In some cases, the symptoms of a fungal infection are very similar to those caused by bacteria or viruses. Whereas drugs used to treat bacterial and viral infections have no effect on fungal infections, a fungal culture helps determine if the cause is a fungal infection. From there, provide an accurate and effective treatment method. Monitoring the effectiveness of the treatment process, monitoring for re-infection can easily happen, because the fungus is difficult to completely treat in the first place. Identifying the right type of fungus, thereby using narrower spectrum drugs, thus preventing antifungal resistance due to indiscriminate use of antifungal drugs. In addition, identifying the cause of the disease helps patients to raise their awareness of preventing the spread of the disease to their loved ones and the community. Accurately distinguishing pathogenic fungi as yeast or filamentous fungi, so that appropriate antifungal tests can be conducted for each type. The fungal culture test is used to accurately identify the causative fungus, which helps to limit the use of the wrong type of antifungal drug, causing the risk of drug resistance. Especially widely used in determining the etiology of some dermatological diseases, respiratory diseases, digestive and genitourinary diseases. Therefore, testing for fungal cultures plays an extremely important role, contributing to more accurate diagnosis and treatment of diseases.
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