Mucosal Candidiasis Workup

Quantitative saliva culture is useful in the diagnosis of oral candidosis. Carriers and patients with oral candidal infection can be distinguished reliably (95% confidence limits) on the basis of quantitative culture, since they harbor more than 400 colony-forming units of candidal organisms per mL of saliva. Ask the patient to rinse his or her mouth for 60 seconds with 10 mL of sterile phosphate-buffered saline (PBS; pH 7.2) or sterile water; then, return the oral rinse to the universal container. If the patient wears a denture, remove it prior to sampling. A rapid commercial system (Microstix-Candida or Oricult-N test) for diagnosing oral candidosis is useful for screening patients in the clinical setting, particularly when microbiology laboratories are not in easy access.

Because Candida species stain poorly by hematoxylin and eosin, staining with periodic acid-Schiff (PAS), Gridley stain, or Gomori methenamine silver (GMS) stain is used. In both Gridley stain and the PAS procedure, fungi appear pinkish red. GMS technique stains yeast cell walls brown-black as a result of deposition of reduced silver. Presence of blastospores and characteristic pseudohyphae or hyphae in the superficial epithelial tissues identifies the fungus as a species of Candida. GMS staining alone cannot perform the speciation of the organism; therefore, cultural studies also should be used.

Blastospores similar to those in Candida species may be seen in histoplasmosis or cryptococcosis, both of which are increasingly prevalent and may manifest orally with increasing frequency in the AIDS epidemic. If only blastospores of candidal organisms are seen in tissue sections of patients in whom infection is suspected, serial sections should be searched carefully for pseudohyphae or hyphae.

As tests of humoral immunity, the candida agglutinin test, candida complement-fixation test, candida precipitin test, immunofluorescence, and enzyme-linked immunoassay (ELISA) have been used. Immunity in superficial candidosis and in oral candidosis is predominantly cell mediated. Cell-mediated immunity to C albicans antigens can be demonstrated in most human subjects both by the appearance of delayed skin hypersensitivity to antigens and by in vitro tests of cellular immunity, such as inhibition of leukocyte migration or stimulation of lymphocyte transformation to candidal antigens.

In the serologic tests, 4 principal types of Candida antigens have been used, including (1) whole nonviable yeast cells, (2) candidal culture filtrates, (3) cell wall polysaccharides or glycoproteins, and (4) cytoplasmic antigens from mechanically disrupted yeast cells. Serologic tests for candidal organisms are not diagnostic tools, since the diagnosis can be achieved more readily by clinical evaluation and by smear or culture.

With regard to hematologic testing, because oral candidosis frequently is associated with HIV disease, nutritional deficiencies, diabetes, or blood dyscrasias, estimates of corrected whole blood folate, vitamin B-12, serum ferritin, glucose, hemoglobin, lymphocyte, and WBC counts can be important. Tests, such as lymphocyte function, serum immunoglobulins, calcium status, or parathyroid hormone levels, are unnecessary except in chronic mucocutaneous candidosis (CMC). Tests of thyroid or adrenocortical function are warranted in selected individuals, since endocrine disorders may be associated with oral candidosis. HIV testing may be indicated.

Although swabs and smears are essential for a microbiological diagnosis of a number of types of oral candidosis, when candidal leukoplakia (chronic hyperplastic candidosis) is suspected, a biopsy specimen should be taken.