Candida albicans

Sample for Candida albicans

1. Scrapings from the affected area.
2. Gram stain of the smear.
3. The culture of the material.
4. The serum of the patient is needed for an antibody test.
5. The serum or body fluid is needed for the presence of the antigens.

Definition of candida albicans

1. Candida organisms may be present as normal flora of the nasopharyngeal area or gastrointestinal tract (20% to 40%).
2. Positive culture of the vaginal secretions in asymptomatic women (10% to 15%)
3. Superficial infection is seen from the oral cavity or vagina.
4. It can be seen as a deep or disseminated infection.
5. The most common opportunistic infections are by:
   1. Candida.
   2. Aspergillosis.
   3. Mucormycosis.

Microbiology of Candida albicans

1. The most common Candida infection in humans is by Candida albicans (90%), followed by Candida tropicalis.
2. Other types are:
   1. C. stellatoidea (subtype is C.albicans).
   2.  C. tropicalis.
   3. C. krusei.
   4. C. guilliermondii.
   5. C. parapsilosis.
   6. Candidiasis is also known as moniliasis.

Characteristic features of Candida albicans:

1. Candida is a normal upper respiratory (nasopharyngeal area), gastrointestinal, and female genital tract flora (20% to 40%).
2. These are oval budding yeast measuring 3 x 6 μm.
3. These are gram-positive.
4. Elongated filament cells joined end to end are called pseudohyphae in vivo.
   1. Candida albicans are the only species to produce hyphae and pseudohyphae in vivo.
   2. Spherical to budding oval cells (3 to 5  x 5 to 10 μm).
   3. Yeast is Y-form.

Candida albicans: Candida in pus

Culture of Candida albicans:

1. These are aerobic and easy to cultivate.
2. Sabouraud’s medium may be made selective by adding the antibiotic (chloramphenicol) and is helpful for primary isolation when incubated at 37 °C for 48 hours.
   1. Other media blood agar shows colonies around the antibiotics disc, which have inhibited bacterial growth.
   2. Colonies are cream to white, flat or hemispherical, and have a waxy appearance.

Candida albicans

Pathogenicity of Candida albicans:

1. The most common areas affected are:
   1. Mucous membranes.
   2. Nails.
   3. Skin.
2. Candidiasis may be:
3. Superficial where it involves:
   1. Mucocutaneous thrush.
   2. Skin in the form of red weeping areas, particularly in the obese person.
   3. In chronic mucocutaneous lesions, there is involvement in the face and scalp.
4. Deep where it involves:
   1. Lower respiratory system.
   2. Urinary tract.
   3. The eyes, meninges, bones, and kidneys are involved in septicemia.
5. It is a yeast-like fungus and usually is present in vaginal secretion.
   1. Candida albicans are present in the upper respiratory, female genital tract, and gastrointestinal tract.
6. Candida albicans is the causative agent in 90% of the cases.
7. The rapid growth of the candida occurs in:
   1. The patients are on long-term antibiotic therapy.
   2. The patients with diabetes mellitus.
   3. The patients are on corticosteroid therapy.
   4. The female during pregnancy.
   5. The ladies on oral contraceptives.
   6. Candida growth occurs in areas not ventilated, like undergarments, and in infants in the diaper area.
   7. Candidiasis has occurred in immune-compromised patients mainly due to T-lymphocytes depression and AIDS.
   8. It may be seen in premature babies.
   9. It is identified in malignancies like leukemia and lymphoma.
   10. It is seen in extensive surgery.

Clinical manifestations of Candida albicans

1. The predisposing factors are:
   1. Aged.
   2. Cachectic or debilitated persons.
   3. People with diseases like AIDS or leukemia.
   4. Drugs are impairing the immune system.
   5. Oral antibiotic therapy.
2. Clinically there may be mucosal candidiasis characterized by laryngitis and esophagitis.
3. Female Patients may have vaginitis, cystitis, and thrush.
4. In the case of acute disease, it may involve the eyes, skin, and muscles when it spreads through blood.
5. Chronic cases have been seen in a patient with neutropenia.
6. Clinically one can see candidiasis as follows:
7. Thrush:
   1. This condition is a very common finding.
   2. It is oropharyngeal candidiasis.
   3. There are white or yellow patches on the tongue or oral cavity with a reddish base covering the mucous membranes.
   4. There is a red area that may involve the throat.
      1. It is difficult to scrape off.

Candida leading to thrush.

2. Diaper rash:
   2. It is seen in infants.
   3. It happens when the wet diaper is left for a longer time.
   4. It is seen in the warm moist areas under diapers and the adults between skin folds (under the breast in females).
3. Genital candidiasis:
   1. It is more common in females than in men. It involves the vagina (monilia).
   2. In the female leads to candida vaginitis and is common during:
      1. Antibiotic therapy.
      2. Oral contraceptives.
      3. During menses.
      4. During pregnancy.

2. S/S of vaginitis:
   2.  There is severe itching in the vagina.
   3. There is vaginal discharge, thick, copious secretion, wetting the undergarments.
   4. On examination, the vagina is inflamed.
   5. Cottage cheese patches appear in white clumps attached to the vaginal wall.
   6. Imidazole suppository helps to treat the disease.
3. Invasive candidiasis:
   1. It takes place through the I/V or catheter when left in the body.
   2. It can enter the brain, heart, and eyes.
   3. It may involve nails and looks like onychomycosis.
   4. Candida albicans lesions are:
      1. Superficial like thrush.
         1. The skin shows a red weeping lesion.
         2. Chronic mucocutaneous candidiasis affects the face and scalp.
      2. Deep lesions are involved in the respiratory system and urinary systems.
         1. Septicemia shows eye, endocardium, meninges, kidneys, and bone lesions.
4. Candida albicans and Candida tropicalis are also seen in conditions like:
   1. Bone marrow transplantation.
   2. Leukemias.
   3. Lymphomas.

Mode of the spread of Candida albicans:

1. It is usually endogenous, but cross-infection may occur like a mother-to-baby and a baby in the nursery.
2. Infections are more common in premature babies.
3. Infection is also more common in debilitated patients and patients with diabetes mellitus.
4. Infection is more common in immunocompromised patients with AIDS, malignancy, leukemias, and lymphomas.
5. It is seen in patients with long-term treatment with antibiotics, immunosuppressive drugs, or cytotoxic drugs.

Laboratory Diagnosis of Candida albicans:

1. Wet film from the affected area can do gram stain.
2. Culture is diagnostic, and culture media used are:
   1. Sabouraud’s medium.
      1. Incubation is done at 37 °C  for 48 hours.
   2. Agar and blood agar.
3. An indirect hemagglutination test may be helpful, but these tests lack sensitivity and specificity.
4. Antigen tests like EIA are available.
   1. A titer greater than 1:8 indicates systemic infection.
   2. The positive test may be seen in mucocutaneous candidiasis or in severe vaginitis.
5. The skin test based on type VI sensitivity is a good diagnostic indicator.
6. Scrapings with KOH preparation may show candida.
   1. It will detect around 60% to 70%of vaginal secretion smears.

Diagnostic features of Candida albicans:

1. Germ tubes are seen when grown in the serum for 3 hours at 37 °C and then make a wet film.
   1. There are filamentous outgrowths like germ tubes.
2. Chlamydospores are seen when grown on a nutrient-poor medium (cornmeal agar) for 24 hours at 28 °C.
   1. There are round, thick-walled resting structures – chlamydospores, usually found at the ends of pseudohyphae deep in the agar.

Candida albicans showing chlamydospore

3. Biochemical activity is a result of fermentation.
4. Antigenic structure: This falls into two groups:
   1. Serotype A.
   2. Serotype B.
5. Antibodies are detected in most of the human sera.
6. A positive skin test is common due to a delayed hypersensitivity (type IV) reaction. This is almost universal in normal adults.
7. Summary of diagnosis:
   1. Wet-mount or stained slide preparation.
      3. KOH (potassium hydroxide) can diagnose in 60% to 70% of the cases.
      4. The use of fluorescent stain (Calcofluor white) increases the detection possibility.
      5. Papanicoula-stained slides are positive in 45% to 50% of the cases.
   2. Culture.
      1. Isolation of candida from blood and urine is suggestive of disseminated candidiasis.
   3. Serologic tests.
      1. Latex agglutination tests are available. These are easy to perform.
      2. IgG EIA procedure is positive in about 82% of the cases for sensitivity.

Treatment of Candida

1. Candida is resistant to all antibacterial drugs because this is a eukaryotic microorganism.
2. Amphotericin B is the drug of choice.
3. For topical use Imidazole  (miconazole, clotrimazole) can be used.
4. Thrush is treated with nystatin, amphotericin B, and miconazole.
5. Systemic lesion needs I/V amphotericin B, either given alone or with 5-fluorocytosine.

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