Fungus, Fungal infections, Diagnosis of Fungal infection
Sample
- The sample can be taken by the pathologist from the patient lesion site.
- The sample can be taken from the following sites.
- SKIN: Scrape the area with a glass slide or knife and get an adequate amount of scrapings on the slide.
- HAIRs: Pluck the hairs with tweezer with roots because the fungus is deep-seated and is near the roots of hairs.
- NAILS: Get from the nail undersurface areas and not from the outer surface.
- Ulcer scrapings.
- Pus.
- Cerebrospinal fluid.
- Blood.
- Bone marrow.
- Urine.
- Stool.
- Bronchial washings.
- Sputum.
- Prostatic secretion.
- Tissue biopsy.
- Blood sample for the antibody test.
Indication
- This procedure is done to diagnose fungal infection.
Pathology
- Fungi are eukaryotic. The fungus nucleus contains multiple chromosomes and the cytoplasm has the mitochondria and ribosomes.
- Chromosomes are surrounded by membranes.
- Growth pattern:
- Many fungi grow sexually (meiosis).
- Some of the fungi grow in filaments (hyphae) and form a mesh called Mycelium.
- Some of the fungi produce buds like yeast is an exception.
- Few of these are pathogenic.
- Fungi are aerobic and can grow on simple media.
- Fungi are classified into:
- Yeast
- These are round to oval unicellular fungi and these can reproduce by budding.
- These reproduce asexually.
- Few may produce pseudohyphae.
- Very few can form true hyphae.
- Examples are Candida, Cryptococcus, and Candida glabrata.
- Yeast
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- Filamentous fungi.
- These are a group of fungi that cause the infection of skin, nails, and hairs.
- These fungi do not involve living tissue.
- These are Trichophyton, Microsporum, and Epidermphyton.
- Filamentous fungi.
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- Dimorphic fungi.
- This exists in two from as molds (mycelial form) and yeast.
- The yeast form is found in the infected tissue and on artificial media at 37 °C.
- Filamentous fungi are present in the soil and grow on artificial media at 22 to 25 °C.
- These are Blastomycosis, Coccidodioides, Histoplasmosis, and Sporothrix.
- Dimorphic fungi.
- Fungal infections are classified into:
- Superficial infection:
- The mucosa leading to Thrush in the mouth by yeast.
- The infection of the nails, skin, and hairs is caused by the filamentous fungi e.g ringworm.
- Subcutaneous infection is caused by the trauma and gives rise to the sinus.
- Systemic infections (mycosis) are serious and fatal for the patient.
- Mycotoxicosis is due to eating the infected food by these fungi and is due to their toxic metabolites e.g. is due to aflatoxin.
- An allergic reaction like type I and type III is mostly due to fungal spores.
- Superficial infection:
Methods to identify the fungus
- Wood’s light (Ultraviolet rays) to see directly fungus over the hairs.
- Then it is examined in the darkroom where infected hair gives fluorescence of bright yellow-green light.
- Phase-contrast microscopy:
- This is quick and no need for any special stains.
- There is a very good identification of fungi.
- Direct microscopic examination:
- Clean the skin with 70% ethyl alcohol.
- The different sites are:
- Make scrapings from the edge of the lesion.
- Pluck the hairs.
- Take a sample from the underneath of the nails, not the outer surface.
- Procedure :
- Add Potassium hydroxide (KOH) 10 to 20% solution.
- Leave this scraping for 10 to 20 minutes for the keratin to be digested.
- Cover with coverglass and can press it to make a thin smear.
- Then under the microscope can see fungal elements like spores or mycelia.
- The culture of various fluids:
- Blood culture: Blood is collected in the special fungal culture media.
- Urine culture: Collect the morning sample which has a good yield.
- Cerebrospinal fluid can be collected for the culture.
- Sputum culture: The sample can be obtained by bronchoscopy or alveolar lavage.
- Culture can be done to identify the fungus on Sabouraud’s media. This is good for the cutaneous or vaginal sample.
- Add antibiotics like chloramphenicol to suppress the growth of bacteria (selective media).
- Brain-heart infusion media with antibiotics and antifungal will prevents bacterial growth and the rapidly growing fungi.
- The fungi are a slow-growing organism.
- Examine daily up to 21 days and daily check the growth.
- Identify the colony’s appearance and pigmentation.
- Transfer the colony to slide and stain with lactophenol cotton blue and cover with the cover glass.
- Examine under the microscope.
- Serological test:
- These are not highly reliable.
- Antibodies are present in 70 to 80% of the patients.
- There may be cross-reaction of the antibodies.
- These serological tests cannot tell recent or old infection.
- with a titer greater than 1: 32 indicate a fungal infection.
- A complement test can be done for the diagnosis of Histoplasmosis and coccidioidomycosis.
- The immunodiffusion test is helpful for the diagnosis of Blastomycosis.
- These are not highly reliable.
- Biopsy of the tissue can be stained with:
- Periodic acid-Schiff (PAS) reaction.
- Silver stain (Gamori’s methenamine silver).
Types of Fungal diseases
- Dermatophytosis where there is the involvement of superficial skin e.g. Athlete’s foot, and Ringworm.
- Other examples are:
- Tinea versicolor.
- Tinea nigra.
- Piedra (white piedra).
- Black Piedra.
- Other examples are:
- Subcutaneous mycosis where there is the involvement of deeper tissue and muscles.
- These will give rise to chronic granulomatous inflammation.
- Sporotrichosis.
- Chromomycosis.
- Mycetoma.
- Systemic mycosis where there is the involvement of deeper tissues and organs.
- Examples are:
- Blastomycosis.
- Histoplasmosis.
- Coccidioidomycosis.
- Paracoccidioidomycosis.
- Examples are:
Treatment
- The superficial infection can be treated by the Clotrimazole or Miconazole.
- A local application like Benzoic acid was also used.
- For severe infection, oral Griseofulvin used for 4 to 6 weeks.
- In the case of hairs used for 3 to 6 months.
- In the case of nails for one year.
- Oral Terbinafine and Itraconazole are also effective.
The information on this web-sit is perfect, and i will pass it on.
Do you know where or who will do these type of blood test in California?
You can try these techniques if facilities are available in California.