Bilateral tonsillectomy is performed on an otherwise healthy 11-year-old female with recurrent upper respiratory tract infections. On pathologcal examination of the tonsils, numerous small, yellow granules are noted. A granule crushed between two slides have a dense, gram-positive center and numerous branching filaments at the periphery. The granules are most likely composed of which of the following organisms?
Correct Answer: Actinomyces israelii
Description: Actinomyces are normal inhabitants of the gastrointestinal tract that grow under anaerobic and microaerophilic conditions. Although they are gram-positive rods, they grow as branching filaments and have been confused with fungi. The yellow colonies (sulfur granules) are found in low-oxygen niches like the tonsils and in actinomycotic abscesses. Aspergillus fumigatus may be present in the respiratory tract as an oppounistic pathogen; however, fungus balls are generally seen only in pre-existing cavities (e.g., bronchiectasis, TB), not in the tonsils. Blastomyces dermatitidis is a respiratory pathogen that is seen as thick-walled yeasts within granulomas. Candida albicans, also a normal inhabitant of the oral cavity, would present as whitish plaques and would appear microscopically as budding yeasts.
Category:
Microbiology
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