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Overview of candida

Candida generally lives inside the body in places like the mouth, throat, gut, & vagina, and skin without causing any problems. Candida albicans is the most common and most pathogenic species of candida infecting humans.

Virulence factors

  • Polymorphism (Phenotypic switching): 3 phenotypic forms in the tissue yeast such as blastospores, pseudohyphae, and true hyphae.
  • Adhesins: Helps in adhesion to the skin ad mucosa.
  • Enzymes (Aspartyl proteinases and serine proteinases)-Help in tissue invasion.
  • Biofilm (also aided by adhesins).
  • Toxins: Glycoprotein extracts of the candida cell walls are pyrogenic similar to the bacterial endotoxins.
  • Pseudohyphae: Indicates active infection; phospholipase released from the hyphal tip may help in an invasion, though not proved.

Predisposing factors:

  • Physiological state: Extremes age (infancy, old age), pregnancy.
  • Low immunity: Patients on steroid or immunosuppressive drugs, post-transplantation, malignancy, HIV-infected people.
  • Patients on broad-spectrum antibiotics-suppresses the normal flora.
  • Others: Diabetes mellitus, febrile neutropenia, and zinc or iron deficiency.

Clinical features:

  • Mucosal candidiasis: The various mucosal manifestations include:
    • Oropharyngeal candidiasis (Oral thrush): It is a white, adherent, painless patch in the human mouth.
    • Candidal vulvovaginitis: It is characterized by pruritus, pain, & vaginal discharge that is generally thin, but may become whitish curd like in severe cases.
    • Balanitis and balanoposthitis (occurring in uncircumcised males).
    • Esophageal candidiasis.
    • Angular stomatitis and denture stomatitis.
    • Chronic mucocutaneous candidiasis.
  • Cutaneous candidiasis:
    • intertrigo: It is characterized via. erythema and pustules in the folds of skin; associated or related with tight fining undergarments and sweating.
    • Paronychia (involving nail-skin interface) and onychomycosis (fungal infection of the nail).
    • Diaper candidiasis: Pustular rashes, associated with the use of diapers in infants.
    • Perianal candidiasis.
    • Erosio interdigitalis blastomycetica: Web spaces of hands or toes.
    • Generalized disseminated cutaneous candidiasis (infants).
  • Invasive candidiasis: results from the hematogenous or local spread of the fungi. Various forms are:
    • Urinary trace infection.
    • Pulmonary candidiasis.
    • Septicemia (mainly by C. albicans and C. glabrata).
    • Arthritis and osteomyelitis.
    • Meningitis.
    • Ocular- keratoconjunctivitis and endophthalmitis.
    • Hepatosplenic candidiasis.
    • Disseminated candidiasis.
    • Nosocomial candidiasis (mainly by C. glabrata).

Genital yeast infection:

  • Candida albicans is the most common causative agent of genital yeast infections.
  • Scientists estimate or approximate that about 20% of women normally have Candida in the vagina without having any symptoms.
  • Candida vaginitis is associated or related to a normal vaginal pH of less than 4.5.

Clinical manifestations:

  • A burning or flaring feeling while having sex or while urinating.
  • An itchy or painful or burning feeling in or around the vagina.
  • Redness, irritation, or swelling around the vagina.
  • Abnormal vaginal discharge can be either watery or thick and white.
  • A rash around the vagina.
  • Pain during sexual intercourse.
  • A rash on the penis.

Vulvovaginal candidiasis:

  • Uncomplicated clinical candidiasis.
    • < 4 episodes in a year.
    • The symptoms are mild or moderate.
    • It is likely caused by Candida albicans.
    • There are no significant host factors such as –poor immune function.
  • Complicated;
    • ≥4 episodes of thrush in a year.
    • When severe symptoms of vulvovaginal inflammation are experienced. Also if coupled or pairing with pregnancy, poorly controlled diabetes conditions, poor immune function is not caused by Candida albicans.
  • Recurrent:
    • About 5-8% of the reproductive age female population.
    • ≥4 episodes of symptomatic Candida infection per year.
    • Results from an especially intense or severe inflammatory reaction to colonization.
    • Candida antigens can be presented or hand out to antigen-presenting cells, which may trigger cytokine production and activate lymphocytes and neutrophils that then cause inflammation and edema.

Laboratory diagnosis of Candida

Specimen collection: Depending on the site of infection,

  1. Whitish mucosal patches.
  2. Skin and nail scrapings.
  3. Sputum.
  4. Urine.
  5. Blood

Direct microscopy: Gram staining reveals gram-positive oval budding yeast cells (4-6μm size) with pseudohyphae.

Culture:

  • SDA ( incubated at 37°C).
  • Blood agar (grow in bacteriological culture media).
  • Colonies appear in 1-2 days and described or explained as creamy white, smooth, and pasty with a typical yeasty odor.

Tests for identification:

Germ tube test (Reynold’s-Braude phenomenon):

The culture of candida treated with sheep/normal human serum is incubated at 37 ◦C for 2-4 hours. No constriction is seen at the point of attachment to the yeast cell. Appear in 2 hours for C. albicans.

Dalmau plate culture: Culture on cornmeal agar can provide a clue for produces thick-walled chlamydospores.

CHROMagar: growth at 45 ◦C: C. albicans can grow.

  • Sugar fermentation test:
  • Sugar assimilation test:
  • Molecular methods: PCR.
  • The urease test is positive.

Immunodiagnosis:

  • Antibody detection: ELISA, Latex agglutination test.
  • Antigen detection: ELISA.
  • Detection of metabolites: Ab, Ag, cell wall components, enolase.
  • Animal pathogenicity/skin tests

Epidemiology:

Candidiasis is one of the three most common vaginal infections along with bacterial vaginosis and trichomoniasis. Approximately 20% of women get an infection yearly. Around 75 percent of women have at least one infection in their lifetime.

Treatment recommendations:

  • For the treatment of uncomplicated (or simple) Candida vulvovaginitis, topical antifungal agents.
  • Alternatively, a single 150-mg oral dose of fluconazole.
  • For severe acute Candida vulvovaginitis, drugs fluconazole 150 mg, given every 72 hours for a total of 2 or 3 doses.
  • For recurring or repeatedly vulvovaginal candidiasis, 10–14 days of induction therapy with a topical agent or oral fluconazole, followed by fluconazole 150 mg weekly for 6 months.
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