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Skin infections

Anti-infective agents key points test

Which of the following statements is true: * Antiseptics commonly result in bacterial resistance *! Antiseptics may cause irritant contact dermatitis * Topical antibiotics rarely cause allergic contact dermatitis * Topical antibiotics are less likely than oral antibiotics to cause bacterial resistance Explanation: Antiseptics do not generally result in bacterial resistance but antiseptics and topical antibiotics they may cause irritant and allergic contact dermatitis. Topical antibiotics more commonly result in allergic contact dermatitis. Bacterial resistance is more commonly induced by topical than systemic antibiotics. Topical antifungal agents are often effective for: *! Localised pityriasis versicolor * Ectothrix infections * Endothrix infections * Complete destruction due to onychomycosis Explanation: Topical antifungal agents are ineffective for fungal hair infection because they do not penetrate to the bottom of the hair follicle. Although useful for limited distal superficial onychomycosis, they are ineffective for extensive nail infections because they do not penetrate through the nail plate to the nail bed or the skin-covered nail matrix. Which of the following statements is true: * Griseofulvin is effective for candidiasis * Itraconazole rarely interacts with other medications *! Terbinafine is available in topical and oral formulations * Ketoconazole is ineffective for pityriasis versicolor Explanation: Terbinafine is available as a topical cream and oral tablets. Azoles are useful for both yeast infections and dermatophytes. Griseofulvin is fungistatic for dermatophytes but is not effective against yeasts. Itraconazole is metabolised with the p450 mitochondrial system and interacts significantly with many drugs potentially resulting in serious adverse effects.