Brain Abscess: Streptococcus intermedius (Streptococcus anginosus group), Finegoldia magna (formerly known as Peptostreptococcus magnus) – Shipped August 10, 2016


A simulated brain abscess sample collected from a 72 year old female inpatient with headache was sent to category A laboratories.

Participants were expected to isolate, identify and report the presence of Streptococcus anginosus group (SAG) and Finegoldia magna. Susceptibility for both organisms was expected however; CMPT recognizes that many laboratories may not be able to test.


  1. Etiologic agents of brain abscesses vary depending on the original source of the infection. They are often related to oropharyngeal flora, infecting through the sinus pathways; as such, Streptococcus anginosus group and anaerobes, especially anaerobic gram-positive cocci, are often implicated.
  2. Streptococus anginosus group is a subset of the viridans group streptococci that has heightened potential for virulence and is commonly implicated in abscesses throughout the body, especially in empyemas, liver, and other intraabdominal abscesses. In such cases comments on general susceptibility may be sufficient since there are often other species associated with the infectious process. In a critical infection such as brain abscess susceptibilities should be performed to ensure that antimicrobial therapy is optimized.
  3. Finegoldia magna is a particularly virulent anaerobic gram-positive cocci. While the speciation of this organism may be difficult, the take home-message is that anaerobic gram-positive cocci should not be taken to be innocuous flora, but rather a large varied group of organisms with a wide spectrum of disease-causing potential.

Full critique (PDF)

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