A 36-year-old female drug abuser has an abscess on her jaw where she lost a tooth from being struck in the face 2 weeks ago. She did not get medical help. You lance the lesion, express some lumpy material with difficulty, and send a swab of the organism to the lab for Gram stain, culture, and susceptibilities. The predominant organism in the Gram stain is a filamentous bacterium that is Gram positive, yet nothing grows in the lab. What is the most likely explanation for why it did not grow?

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Quizplus · Accepted Answer

Your organism is most likely an anaerobe, most probably Actinomyces, that did not tolerate transport aerobically. Unless you ask for specimens to be collected anaerobically or at least ask the lab to culture an abscess, it will not be cultured anaerobically, especially when you send it in on a swab. The clinical case suggests an organism from the gingival crevices and not Staphylococcus aureus as the cause. Large-bore needle biopsy with the specimen sent in the syringe and anaerobic culture should have been done instead. It will likely require debridement by an oral surgeon and antibiotics for several weeks.

A 36-Year-Old Female Drug Abuser Has an Abscess on Her