Candidiasis

Candidiasis
Agar plate culture of Candida albicans

Candidiasis Main page
Patient Information
Overview
Causes
Classification
Pathophysiology

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1];Associate Editor(s)-in-Chief: Ahmed Younes M.B.B.CH [2]

Overview

Candida is a normal commensal of the skin and mucous membranes. The balance between the virulence of the fungus and the host immune defense is responsible avoiding opportunistic infection of candida. Deficiency of cell-mediated immunity or poor general status are the main risk factors for having opportunistic candidiasis. Candidiasis is usually localized to skin and mucous membranes. In rare cases, candidiasis can spread causing candidaemia and distant infection. These cases are usually associated with deficient immunity C. albicans is the main species causing infection in humans more than any other candida species.

Causes

Candida Albicans is responsible for the majority of Candida infections.

Localized candidiasis

Oral and esophageal candidasis:

• Candida albicans accounts for majority of the cases followed by some non albicans species as C. krusei and C. glabrata.

Candida vulvovaginitis:

• Candida albicans: These strains are isolated in 85 to 95% patients with yeast infection.
• Candida non albicans: Candida glabrata is the most common isolated pathogen in this group affecting 10 to 20% of women and is associated with recurrent Candida vulvovaginitis.

Chronic mucocutaneous candidiasis:

• C. albicans are the most isolated species.

Invasive candidasis

Candidaemia:

• C. albicans is the most common isolated organism. However, some non C. albicans species were isolated beside C. albicans.
• In severely immuno-copromised patients, non C. albicans species were isolated alone.

Candida endocarditis:

• Among causes of fungal endophthalmitis, Cadida albicans and non candida albicans species are the 2 most common causes. However, Non albicans species are slightly more prevalent.

Candida osteoarticular disease:

• C. albicans is the most common cause. However, C. glabrata and C. tropicalis are also involved.

Classification:

Candidiasis can be classified according to the site of infection into:

Candidiasis

Localoized mucocutaneous candidiasis

Invasive Candidiasis

Oropharyngeal candidiasis

Esophageal candidiasis

Candida vulvovaginitis

Chronic mucocutaneous candidiasis

Candidaemia

Candida endophthalmitis

Candida endocarditis

Candida osteoarticular disease

Pathophysiology

Candida is a normal commensal of skin and mucous membranes. A competent immune system and an intact regenerating healthy skin prevent the virulence of Candida.

Candida Virulence factors

The main virulence factors that mediate the infection:

• Secreting molecules that mediate adherence into host cells
• Production of hydrolases which has a lytic effect on tissues and facilitate the invasion by the fungus.
• Polymorphism: Candida has the ability to grow either as pseudohyphae (elongated ellipsoid form) or in a yeast form (rounded to oval budding form. While the role of polymorphism is not clearly understood in the virulence of Candida, it’s noted that the species that are capable of producing the most severe form of the disease has this ability.
• Biofilm production: which means the ability to form a thick layer of the organism on the mucosal surfaces or even on catheters and dentures.

Patients with candida vulvovaginitis were found to have decreased levels of mannose binding lectins (MBL) . Further investigations revealed that 2 genetic mutations in genes responsible for MBL and IL4 production increase the host susceptibility of getting recurrent candida vulvovaginitis.

Host immune defects

Any condition that compromises cell mediated immunity, worsens the general status of the patient or provide a favorable medium for Candida to form biofilms put the patient at increased risk for having candidiasis.

Conditions that compromises cell mediated immunity:

• T cell deficiencies as in DiGeorge syndrome, Wiscott-Aldrich syndrome and Ataxia-telangiectasia.
• Bone marrow transplant
• Leukaemias
• Corticosteroids use or immunosuppresive drugs.

Conditions that worsens the general condition:

• Malignancies
• Recent chemotherapy
• Trauma
• Recent surgery
• Prolonged hospitalization
• Broad-spectrum antibiotics
• Renal failure
• Haemodialysis (especially if prolonged)

Dentures that provide a favorable media for forming biofilms:

• Prolonged central venous catheters insertion
• Prolonged foley’s catheter insertion
• Prolonged mechanical ventilation