Fungal Infections in the mouth are almost exclusively caused by the yeast Candida albicans. It is a normal oral parasite and is found in the oral cavity of as many as 20-50% of symptomless individuals.
Clinical fungal infection develops when the host's resistance is impaired and the natural balance of the oral flora becomes disturbed. Fungal infection is therefore a sign of either a local or systemic impairment of the host's resistance.
Local predisposing factors include the lack of normal bacterial flora in newborn babies, poor oral hygiene in denture wearers, reduced salivation, smoking and inhaled glucocorticoids.
In modern clinical practice Fungal Infections of the Mouth are considered to be either primary or secondary.
Primary Fungal Infections can be acute, chronic, associated with candidal infection or they may be keratinised lesions superinfected by fungal infection.
The most common form of the acute infections is the erythematous type where mildly painful diffuse reddish areas of varying size are seen on the oral mucosa. The acute pseudomembraneous type (oral thrush) is characterised by light-coloured patches that coat the oral mucosa to varying extent and that can be scraped off.
A chronic infection may be either erythematous or pseudomembraneous (picture 1). A chronic infection may also manifest itself as lesions with hyperplastic, nodular or plaque-like appearance that cannot be scraped away.
Conditions associated with candidal infection are denture stomatitis, angular cheilitis (picture 2) and median rhomboid glossitis (see Benign Lesions of the Tongue; picture 3).
Fungal culture sample from the oral mucosa. The sample is collected to a gel-containing transport tube (e.g. Transpocult® ) ordered from the microbiology laboratory. The patient may also visit the laboratory for sample taking.
The culture report indicates the fungal species found and their quantities on a plus scale (+, ++, +++). Two or three pluses suggest an infection to be treated. The symptoms and clinical findings should, however, be taken into account when making treatment decisions.
A smear specimen can be taken from a lesion or from the oral mucosa on a microscope slide. It is fixed with alcohol or a special fixative and sent directly to the pathology laboratory for examination. If there is a need to take a biopsy, it can be examined with PAS staining for possible candidal infection.
Commercial products for cultivating and detecting Candida at the surgery are available. The sample is incubated for e.g. 18-48 hours in an incubator, or longer in room temperature. The results are interpreted according to instructions in the package.
Treatment
If only possible, treatment is always based on the elimination of local and systemic factors that predispose the patient to candidal infections.
In patients wearing dentures, rebasing or renewal of these should be considered. Dentures should be daily brushed using e.g. a dishwashing liquid, taken out of the mouth for the night and stored dry.
During the antifungal medication, the dentures should be disinfected daily, then once a week.
Possible disinfectant agents to be used: 0.2% chlorhexidine solution, 0.02% sodium hypochlorite solution, or effervescent denture cleansing tablets. After 15-30 min of disinfection the dentures are carefully rinsed with water.
Drug therapy is prescribed if the clinical signs are suggestive of fungal infection and the patient is symptomatic, e.g. has stinging, burning or tenderness of the mouth. It is advisable to confirm the diagnosis also with culture or from a smear/biopsy.
Topical drug therapy (the most recommended); treatment is continued for at least one week after the symptoms have disappeared (the prescription can be written for e.g. 4 weeks)
Nystatin oral suspension (100 000 IU/ml) 1-5 ml 3-4 times daily
Miconazole 20 mg/g or 2% oral gel, 2.5 ml every 6 hours (may require special permit)
Note the possibility of drug interactions (e.g. with warfarin) in association with the use of miconazole gel!
Amphotericin B 10 mg lozenges, 1 tablet 4 times daily; duration of treatment usually about 2 weeks, which may be extended, as required, according to the clinical picture (may require special permit)
Primarily fluconazole 200-400 mg once on the first day, then 100-200 mg once daily for 1-2 weeks
In patients receiving treatment for cancer the doses may be larger and the duration of treatment longer. For prophylaxis in cancer patients 200-400 mg once daily.
If there is no response to fluconazole, it is recommended to take a specimen for antifungal drug sensitivity testing and to plan further treatment accordingly.
Note: azole antifungal agents may have harmful interactions with a number of other drugs, e.g. warfarin. The risk of azole resistance has to be taken into account when treating recurrent oral candidosis.
References
Pappas PG, Kauffman CA, Andes DR et al. Clinical Practice Guideline for the Management of Candidiasis: 2016 Update by the Infectious Diseases Society of America. Clin Infect Dis 2016;62(4):e1-50. [PubMed]