Infectiology & General Medicine
Oral thrush - Thrush
Oral candidiasis - commonly known as thrush - is an opportunistic fungal infection of the oral mucosa caused mainly by Candida albicans, a commensal yeast naturally present in the oral, digestive and genital flora of 30 to 60 % healthy adults. Under normal physiological conditions, the growth of Candida albicans is controlled by the balance of the commensal bacterial flora, by local immunity mechanisms (secretory IgA, neutrophils, macrophages) and by the conditions of the oral environment (pH, salivary flow, mucosal integrity). Oral candidiasis occurs when this balance is upset - by disturbance of the flora (broad-spectrum antibiotic therapy), reduced immunity (HIV/AIDS, corticosteroid therapy, chemotherapy, poorly controlled diabetes) or altered local conditions (xerostomia, dental prostheses, corticosteroid inhalation). Oral candidiasis is extremely common in certain populations: it affects 5 to 7 % of infants in the first few weeks of life (contamination via the genital tract, colonized in 25-35 % of pregnant women), 10 to 15 % of patients with dental prostheses, 30 to 40 % of patients undergoing chemotherapy or cephalic radiotherapy, and up to 90 % of patients with advanced AIDS (CD4 < 200/mm³) before the era of antiretrovirals. While oral candidiasis is generally a benign superficial infection in immunocompetent subjects, it can be a sentinel sign of undiagnosed underlying immunodepression in adults without any obvious triggering factor, and can progress to esophageal candidiasis (dysphagia) or systemic disseminated candidiasis (potentially fatal) in severely immunocompromised patients.
Risk factors
- Broad-spectrum antibiotic therapy: the most common cause of oral candidiasis in current practice - antibiotics destroy the commensal oropharyngeal bacterial flora that normally competes with Candida for nutritional resources and mucosal adhesion sites → uninhibited fungal growth (dysbiosis); the risk is proportional to the duration and breadth of the antibiotic spectrum; broad-spectrum beta-lactams (amoxicillin-clavulanate), fluoroquinolones, 3rd-generation cephalosporins and carbapenems are the most concerned
- Inhaled corticosteroid therapy (asthma, COPD): oropharyngeal candidiasis due to local deposition of the inhaled corticosteroid on the buccal and pharyngeal mucosa → local immunosuppression (inhibition of local macrophages and neutrophils) → proliferation of Candida ; prevalence of 5 to 15 % depending on molecule and inhalation technique; prevention: systematic rinsing of mouth and throat after each inhalation, use of an inhalation chamber (spacer)
- Systemic corticosteroid therapy and immunosuppressants: oral or IV corticosteroids in doses > 10-20 mg/day prednisone equivalent for more than 2 weeks → systemic immunosuppression → oral candidiasis and risk of dissemination; immunosuppressants (cyclosporine, tacrolimus, mycophenolate mofetil - transplant recipients) ; biotherapies (anti-TNF, anti-IL-17, anti-IL-23 - anti-IL-17s such as secukinumab or ixekizumab are particularly associated with mucosal candidiasis, as IL-17 is a key cytokine in anti-ILF immunity).Candida)
- HIV/AIDS and severe immunodepression: oropharyngeal candidiasis is the most frequent opportunistic infection of HIV - affecting up to 90 % of AIDS patients (CD4 < 200/mm³); its presence in an adult with no obvious risk factor should systematically prompt HIV screening; other severe immunodepressions: leukemias and lymphomas, post-chemotherapy neutropenia (CD4 and polymorphonuclear cells < 500/mm³), stem cell allografts
- Poorly balanced diabetes mellitus: hyperglycemia promotes the proliferation of Candida (glucose is the fungus' main energy substrate), alters the function of neutrophils and macrophages (phagocytic dysfunction) and modifies the composition of saliva (high salivary glucose levels, reduced salivary flow); recurrent oral candidiasis may reveal undiagnosed or poorly controlled diabetes.
- Xerostomia (dry mouth): saliva plays a major antifungal role - it contains lactoferrin, lysozyme, peroxidases, secretory IgA and protective mucus; a reduction in salivary flow (< 0.1 mL/min at rest) favours colonization of the mucosa by Candida ; causes: Sjögren's syndrome, salivary gland radiotherapy (doses > 26 Gy → permanent xerostomia), anticholinergic drugs (tricyclic antidepressants, antihistamines, antimuscarinics, some antipsychotics), chronic dehydration
- Removable dental prostheses: the underside of the prostheses - in contact with the palatal mucosa - forms an enclosed, warm, moist space that is difficult to clean, where Candida incorporates into the denture biofilm; subprosthetic candidiasis (prosthetic stomatitis) affects 15 to 65 % of wearers of removable dentures; aggravating factors: wearing the denture 24 hours a day (including at night), inadequate cleaning, poorly fitted denture causing microtrauma to the mucosa
- Infants and the elderly: infants have immature mucosal immunity and an as yet unestablished oral flora → frequent thrush (5-7 %) in the first few weeks; the elderly often have a combination of several factors: drug-induced xerostomia, prostheses, polypharmacy including corticoids or antibiotics, immunosenescence
Clinical forms
| Clinical form | Description and presentation | Population concerned |
|---|---|---|
| Pseudomembranous candidiasis (classic thrush) | Whitish or creamy deposits easily detachable with a tongue depressor, revealing an underlying erythematous and sometimes hemorrhagic mucosa; located on the tongue, palate, cheeks, gums and pharynx; metallic or bitter taste, burning, difficulty swallowing; acute form (antibiotic therapy, onset of immunodepression) or chronic form (HIV, long-term immunosuppressive therapy). | All ages, especially infants and the immunocompromised |
| Erythematous (acute atrophic) candidiasis | Painful erythematous areas without whitish deposits - often on the back of the tongue (lingual depapillation - smooth, red, shiny tongue) or on the hard palate; most frequent form after antibiotic therapy and on inhaled corticosteroids; often underdiagnosed because absence of white deposits wrongly rules out the diagnosis. | Adults on antibiotics or inhaled corticosteroids |
| Prosthetic stomatitis (chronic atrophic candidiasis) | Chronic erythematous palatal mucosa under the prosthesis - asymptomatic in 90 % of cases (incidental discovery during dental examination); sometimes slight burns; Newton classification (type I: localized erythema around salivary gland orifices; type II: diffuse erythema; type III: granular or papillary surface) | Removable denture wearers |
| Angular cheilitis (candidiasis) | Fissures, erythema, scabs and maceration at the labial commissures - often bilateral; can be mixed (candidal + bacterial) Staphylococcus aureus); favored by worn prostheses that reduce bite height (sagging of the commissures), saliva maceration, iron, vitamin B12 or zinc deficiency | Elderly people, prosthesis wearers, nutritional deficiencies |
| Chronic hyperplastic oropharyngeal candidiasis | Thick, firm, non-detachable whitish plaques (unlike classic thrush), localized on the cheeks - may be confused with precancerous leukoplakia; biopsy often required to confirm diagnosis and exclude epithelial dysplasia; systemic antifungal treatment required; often in the context of chronic immunosuppression or heavy smoking | Adults, smokers, chronic immunocompromised patients |
| Esophageal candidiasis (extension) | Extension of oropharyngeal candidiasis to the oesophagus - painful dysphagia with solids and liquids, odynophagia (pain on swallowing), retrosternal burning sensation; may occur without obvious oral thrush in HIV patients or those on heavy immunosuppressants; diagnosis by endoscopy (adherent white patches on friable mucosa) or by response to empirical antifungal therapy; oral or IV systemic treatment depending on tolerance | HIV (CD4 < 200), transplant patients, chemotherapy |
ℹ️
Oral candidiasis in adults with no apparent risk factors (no recent antibiotic therapy, no corticosteroids, no dental prostheses) should be investigated for underlying undiagnosed immunosuppression - in particular HIV infection (HIV serology), diabetes (fasting blood glucose), haematological malignancy (CBC) or unrecognized immunosuppressive therapy. Do not treat empirically without assessing the underlying cause.
Diagnosis
- Clinical diagnosis: in the vast majority of cases, diagnosis is clinical - appearance of detachable whitish deposits on tongue depressors (pseudomembranous form) or characteristic erythematous areas in patients with identified risk factors; the tongue depressor detachment sign (deposits withdraw, leaving a red mucosa) helps distinguish thrush from leukoplakia (non-detachable) or aphthae
- Mycological examination: smear of the oral mucosa with a sterile swab → direct microscopic examination after PAS (periodic acid-Schiff) or calcofluor white staining - visualization of budding yeasts and pseudohyphae (filaments) characteristic of the invasive form of Candida albicans ; culture on Sabouraud medium (results in 48-72 hours) - identification of species and antifungi if resistance suspected; positive cultures alone do not distinguish colonization from infection (context-dependent diagnostic value of smear)
- Biopsy: reserved for chronic hyperplastic forms to exclude dysplasia or squamous cell carcinoma.
- Etiological workup (if candidiasis without obvious factors): fasting blood glucose (diabetes), CBC (hemopathy, neutropenia), HIV serology, immunoglobulin assay, cortisol and adrenal workup if adrenal insufficiency suspected.
Treatment
| Clinical situation | Treatment and dosage |
|---|---|
| Mild to moderate oral candidiasis (immunocompetent) | Nystatin oral suspension (100,000 U/mL) - 1-2 mL mouthwash 4 times/day, 2 minutes before swallowing, for 7 to 14 days; effective in 80 % of cases in immunocompetent patients; alternative: miconazole oral gel 2 % (Daktarin) - 2.5 mL 4 times/day in the mouth; local and slightly systemic action; important drug interactions (warfarin - increased INR, antidiabetics, statins). |
| Moderate to severe or recurrent oral candidiasis (immunocompetent) | Fluconazole oral 150 mg single dose OR 100 mg/day for 7 to 14 days - reference systemic treatment; spectrum on C. albicans (excellent) and most Candida non-albicans except C. krusei (intrinsic resistance) and C. glabrata (reduced sensitivity); well tolerated; drug interactions (warfarin, some statins, benzo) via CYP450 2C9/3A4 |
| Oral candidiasis on inhaled corticosteroids | Nystatin or local miconazole in 1st intention; optimize inhalation technique (spacer inhalation chamber mandatory) and systematic mouth/throat rinsing after each inhalation; if recurrent despite local measures: fluconazole 100 mg/week as discontinuous prophylaxis. |
| Thrush | Nystatin suspension 100,000 U/mL - 1 mL 4 times/day after feedings, for 7 days (apply with dropper to lesions); miconazole oral gel not recommended before 4 months (risk of choking) and contraindicated before 6 months according to new recommendations; simultaneous treatment of the mother's genital or mammary candidiasis if breast-feeding. |
| Prosthetic stomatitis | Nystatin or local miconazole 14-28 days + daily disinfection of the prosthesis (soak 30 min in a solution of chlorhexidine 0.1 % or chlorhexidine gluconate); removal of the prosthesis at night mandatory; replacement or relining of the prosthesis if poorly adjusted - treatment of the mechanical cause essential; almost systematic recurrence without treatment of the prosthesis. |
| Angular cheilitis | Local antifungal cream (nystatin or miconazole) ± antibacterial cream (fucidic acid or mupirocin) if bacterial superinfection is suspected; correct the contributing factors (adapt the prosthesis, supplement with iron/B12/zinc if deficiency is documented). |
| Oral candidiasis in HIV or severely immunocompromised patients | Fluconazole 100-200 mg/day 7-14 days - reference treatment; if resistance to fluconazole (C. glabrata, C. krusei): itraconazole oral solution 200 mg/day, voriconazole 200 mg ×2/day or posaconazole 400 mg ×2/day; echinocandins (caspofungin, micafungin, anidulafungin IV) if severe form, refractory esophagus or candidemia; secondary prophylaxis with fluconazole weekly if recurrences > 3/year; optimization of antiretroviral treatment (immune reconstruction) - most effective measure to prevent recurrences. |
| Esophageal candidiasis | Fluconazole oral 200-400 mg/day 14-21 days - reference treatment; alternatives: itraconazole 200 mg/day, voriconazole 200 mg ×2/day; if severe dysphagia preventing oral intake: fluconazole IV 200-400 mg/day; follow-up endoscopy if unfavourable evolution under treatment. |
Signs requiring rapid medical assessment
Seek immediate medical attention if thrush is accompanied by dysphagia or odynophagia (difficulty or pain in swallowing) - which may indicate esophageal extension requiring systemic treatment; if symptoms persist or worsen after 7 to 14 days of well-managed local antifungal treatment; if oral candidiasis is recurrent with no identified cause (more than 2 episodes per year) - systematic etiological work-up required; or if you are severely immunocompromised (HIV, chemotherapy, transplant) with associated fever - risk of disseminated candidemia requiring hospitalization and IV systemic antifungal treatment.
Consult at Clinique Omicron
Clinique Omicron's physicians diagnose and treat oral candidiasis, prescribe antifungal agents adapted to the severity and clinical context, perform an etiological workup in cases of recurrent candidiasis or candidiasis without obvious triggers, and screen for HIV, diabetes or other underlying immunodepressions. Consultations are available at our points of service in Quebec, as well as via telemedicine. To book an appointment, visit cliniqueomicron.ca.
The contents of this page are provided for information purposes only and do not replace the advice of a qualified healthcare professional. Recurrent or treatment-refractory oral candidiasis always warrants medical investigation to identify and treat the underlying cause.
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