Causes and Management of Oral Thrush

Primary Causative Organisms

• Candida albicans is the most common pathogen responsible for oral thrush, accounting for the majority of cases 1, 3
• Non-albicans Candida species such as C. glabrata, C. dubliniensis, and C. krusei can also cause oral thrush, particularly in cases of fluconazole resistance 1, 4
• C. dubliniensis was first identified in association with oral candidiasis in HIV-infected patients 1

Predisposing Factors

Systemic Factors

• Immunosuppression is a major risk factor, particularly in HIV infection with CD4+ counts <200 cells/μL 4, 5
• Use of corticosteroids, including inhaled steroids, can increase the risk of oral thrush 4
• Radiation therapy to the head and neck can also increase the risk of oral thrush 4

Pathophysiology

• Candida species normally exist as commensals in the oral cavity but can become pathogenic when the balance of oral microflora is disrupted 1
• Host defense mechanisms being compromised can lead to the transition from commensal to pathogen 5

Antifungal Resistance

• Acquired fluconazole resistance is related to previous exposure to these medications, particularly if repeated and prolonged in the context of profound immunosuppression 1, 2
• The emergence of non-albicans Candida species with intrinsic reduced azole susceptibility often follows repeated antifungal exposure 1, 2

Clinical Relevance

• Oral thrush can present in three main clinical patterns: pseudomembranous candidiasis, erythematous candidiasis, and angular cheilitis 1, 3
• The presence of erythematous and pseudomembranous forms in HIV-infected patients is predictive of progressive immunodeficiency 1

Prevention Strategies

• Effective antiretroviral therapy is the best prophylaxis against recurrent oral thrush in HIV-infected patients 4, 5
• While fluconazole prophylaxis can reduce the risk of mucosal candidiasis in high-risk patients, routine primary prophylaxis is not recommended due to concerns about drug resistance development 5