An 85-year-old female wearing maxillary and mandibular complete dentures fabricated 5 years ago presents with 'The corners of my lips are all chapped!' She has hypertension and urinary incontinence and takes amlodipine (Norvasc®). Erythema and white patches are noted around the oral commissures with no intraoral lesions. Which main etiologic agent would be most likely responsible for her symptoms?

Correct answer: B. Fungi and bacteria

• A. INCORRECT. Viruses are not typically implicated in angular cheilitis. Herpes labialis affects the vermilion border and perioral area, but the presentation described (erythema and white patches at commissures in a denture-wearing patient) is characteristic of angular cheilitis, which has a bacterial-fungal etiology.
• B. CORRECT. Angular cheilitis (perlèche) is an inflammatory condition at the corners of the mouth caused by a mixed infection of fungi (primarily Candida albicans) and bacteria (primarily Staphylococcus aureus and beta-hemolytic streptococci). In elderly denture wearers, loss of vertical dimension causes skin folding at the commissures, creating a moist environment ideal for this polymicrobial infection.
• C. INCORRECT. Bacteria can be part of the polymicrobial picture in angular cheilitis, but viruses are not typical causative agents. The predominant organisms are Candida and bacteria.
• D. INCORRECT. Bacteria alone (without fungal involvement) are not sufficient to explain the white patches seen in this case. The white patches suggest Candida overgrowth, which requires antifungal treatment in addition to antibacterial therapy.