Medical Microbiology and Infection

at a Glance

Fourth EditionStephen Gillespie and Kathleen Bamford

Case Studies

Case 22

A 44-year-old man who presented with an episode of collapse described a 2-week history of fatigue, agitation, confusion and left arm weakness, but no headaches, visual problems, vomiting, seizures or dental pain. On examination he is found to be febrile. He has a reduced level of consciousness.

  • 1. What is the differential diagnosis?

    Reduced consciousness and fever should make one consider bacterial meningitis, cerebral malaria, brain abscess or cerebral haemorrhage

  • 2. What does the absence of papilloedema suggest?

    The history of this presentation is short so the absence of papilloedema does not exclude raised intracranial pressure.

  • 3. What investigation is required now?

    A CT scan is necessary to determine whether there is any raised intracranial pressure.

  • More info: A CT scan showed left frontal and right parietal lobe abscesses.
  • 4. What is the most appropriate treatment?

    The patient should be commenced on a regimen that includes a third-generation cephalosporin and metronidazole.

  • 5. What additional treatment should be considered?

    For diagnosis and therapy the abscess could be drained.

  • More info: A sample of pus from a brain abscess was sent to the laboratory for microscopy and culture, where a few white blood cells and numerous Gram-positive cocci were seen. α-haemolytic streptococci grew on routine culture media. The isolate was identified by biochemical testing to be Streptococcus parasanguis. A 16S rRNA gene PCR, followed by sequencing was performed and the isolate was identified as Streptococcus intermedius.
  • 6. How would you interpret these results?

    The molecular identification is more likely to be correct. Streptococcus parasanguis is usually found as a commensal in the mouth, whereas Streptococcus intermedius is capable of causing abscesses throughout the body.

  • 7. How would these results affect the treatment?

    The streptococcus will be sensitive to the cephalosporin and treatment should continue as before.

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