Identification of Streptococcus intermedius Central Nervous System Infection by Use of PCR and Electrospray Ionization Mass Spectrometry

We describe the utility of PCR and electrospray ionization with mass spectrometry (PCR/ESI-MS) of culture-negative cerebrospinal fluid (CSF) in order to identify Gram-positive cocci noted on a Gram stain of CSF from a previously healthy 26-year-old man with community-acquired pneumonia (CAP) and multiple brain abscesses. CSF samples were obtained 2 weeks apart, first by lumbar puncture and 2 weeks later from an external ventricular drain that was inserted into the right ventricle. Both CSF cultures were negative. A Gram stain of bronchoalveolar lavage (BAL) fluid was notable for many Gram-positive cocci (GPC), but cultures of BAL fluid and subcarinal lymph node biopsy tissue were negative. PCR/ESI-MS detected Streptococcus intermedius, a common cause of brain abscesses, in both CSF samples as well as in the fixed tissue from the biopsy. This unique case confirms S. intermedius pulmonary infection as the source of metastatic CNS infection and reveals the potential of PCR/ESI-MS to detect a streptococcal pathogen not captured by conventional cultures.