Infections caused by Candida species are the most common oral infections (candidiasis). Candida is present as a commensal intra-orally in majority of the population.
It is an opportunistic pathogen, with the most common being Candida albicans, though other Candida species have been identified. It is a dimorphic fungus, present in both yeast (blastospore) and filamentous (hyphae) forms.
Protective mechanisms against Candida
There are 3 main methods protecting the mouth from candidiasis:
- Saliva – this carries out a mechanical cleansing action as well as containing components of the immune system.
- Epithelium – this behaves as a physical barrier to microbes as well as containing immunological cells.
- Other microbes – the presence of other microbes, particularly bacteria, creates competition for the Candida and prevents infection.
If any of these systems fail, a person becomes susceptible to candidiasis.
Predisposing factors for Candidiasis
Being an opportunistic pathogen, a predisposing factor is generally present to allow infection. Sometimes, candidiasis can be referred to “as a disease of the diseased“.
- Age – the elderly and the very young, due to poor immune function or other predisposing factors as below.
- Dentures – denture wearing and poor denture hygiene are common causes. Patients who fail to clean their dentures or keep their dentures in during the night will commonly present with forms of candidiasis. Poorly constructed dentures, causing overclosure, can lead to candidiasis at the corners of the mouth.
- Xerostomia – this alters the ability of saliva to act as a mechanical cleanser as well as a part of the immune system.
- Antibiotics – particularly broad-spectrum antibiotics, eliminate the competition from bacteria intra-orally, hence favouring candidiasis.
- Immunosuppression/Immunodeficiency – any factor causing a reduction in the functioning of the body’s immune system is likely to favour candidiasis, including conditions such as HIV/AIDS. The use of steroid medication, both systemic and topical, will suppress the immune system.
- Smoking – smoking is thought to favour Candida growth.
- Diet – malnutrition, particularly in gastro-intestinal conditions and with a poor diet, will lead to deficiencies. Haematinic deficiencies (iron, B12 and folate) are commonly associated with candidiasis.
- Other – general abnormalities in the epithelium, due to conditions such as lichen planus, can favour candidiasis. Uncontrolled diabetes is also linked with candidiasis.
Forms of Candidiasis
Candidiasis can be broadly divided in to acute forms and chronic forms.
Diagnosis is usually made on clinical appearance, however further investigations can be carried out.
Management usually involves the following (any variations are stated):
Any persistent or recurrent candidal infections should be treated with caution and underlying causes should be identified – particularly the potential of deficiencies and HIV.
Acute Pseudomembranous Candidiasis (Thrush)
- The most common presentation of candidiasis (around 35% of cases).
- Can be a chronic condition in those with long-term immunosuppression.
- Presentation: creamy, white patches that can be wiped off to reveal underlying erythematous mucosa. The white patches are composed of Candida, fibrin and epithelial cells. Common locations include buccal mucosa, tongue and palate.
- Investigations: oral rinse (general Candida count); oral swab (culture and sensitivity of specific area); identify underlying cause.
- Treatment: as above.
Acute Atrophic Candidiasis
- Usually caused by antibiotics (‘antibiotic sore mouth’), chemotherapeutic agents and steroids.
- Presentation: Typically raw, erythematous and painful lesions, commonly on the dorsum of the tongue (also the palate when steroid inhalers are used). The tongue often has a depapillated appearance.
- It resembles the ‘red background’ in thrush, without the overlying pseudomembrane.
- Treatment: as above.
Chronic Atrophic Candidiasis
- Denture-related Candidiasis
- Also known as denture stomatitis. Associated with poor denture hygiene. Present in half of denture wearers. Most commonly the upper arch.
- Presentation: Usually asymptomatic, with erythema and inflammation evident across the denture-bearing area.
- Good denture hygiene – keep denture out at night, clean denture with Corsodyl or Milton’s as appropriate.
- Brush the denture-bearing areas effectively. Chlorhexidine mouthwash can also be prescribed.
- Topical agents as above.
- Median Rhomboid Glossitis
- Presentation: Rhomboid shaped, depapillated lesion on the midline dorsal surface of the tongue. There may be some erythema and be smooth. Typically asymptomatic. Patients may develop a ‘kissing lesion’ on the palate.
- Treatment: May be conservative or as above.
- HIV-related Candidiasis
- Candidal infections are a common oral infections in approx. 90% of AIDS and 25% of HIV patients. This is due to the immunocompromised state.
- Presentation: Pseudomembranous forms and erythematous forms (commonly median rhomboid glossitis) are the commonest forms. Patients may also present with linear gingival erythema, which is a linear band of gingivitis. They may also develop necrotising ulcerative periodontal conditions.
- There are many reasons for development and may even be multifactorial:
- Reduced vertical dimension – creates the ideal environment for fungal growth. This may be due to poor denture design.
- Existing oral candidal infection
- Nutritional deficiencies – particularly iron, B12 and folate.
- Stress or being rundown
- General immunosuppression – particularly if a patient is currently ill.
- Infections may also be associated with Staph. aureus.
- Presentation: Erythema, soreness with fissuring at the angles of the mouth. May be unilateral but usually bilateral.
- Investigations: oral rinse (general Candida count); oral swab (culture and sensitivity of specific area); blood tests, identify underlying cause.
- Identify and treatment underlying cause
- Anti-fungal agents as above.
- May also prescribe sodium fusidate ointment 2% QDS – this will provide cover for both bacterial and fungal components.
Chronic Hyperplastic Candidiasis
- The only premalignant lesion – 25% risk of malignant change. It is associated with tobacco and alcohol use.
- Presentation: Persistent white/speckled patch that does not rub off. Most commonly found at the oral commissures. It may be irregular, rough or nodular in appearance as well.
- Investigations: Incisional biopsy should be carried out to assess for dysplasia and malignant change, particularly if not responding to anti-fungal treatment.
- Smoking cessation advice
- Systemic anti-fungal agents as above (usually for 2 weeks and review). Rarely topical agents.
Chronic Mucocutaneous Candidiasis
- These are an extremely rare group of syndromes characterised by persistent superficial candidal infections of the mucosae, nails and skin.
- There are multiple forms including localised chronic, diffuse and candidosis-endocrinopathy types.
- Candida infections tend to occur in those with a predisposing factor e.g. immunosuppression, deficiencies or poor oral health.
- There are multiple forms that can be broadly divided in to acute and chronic forms.
- The most common form is pseudomembranous candidiasis. Chronic hyperplastic candidiasis has a 25% chance of malignant change.
- Clinical diagnosis may be sufficient, but further investigations including swabs, oral rinses and biopsies may be needed where appropriate.
- Management predominately involves identifying and treating the predisposing factor, along with potentially topical and systemic anti-fungals.