AUTHOR=Issa Elio , Salloum Tamara , Tokajian Sima 

TITLE=From Normal Flora to Brain Abscesses: A Review of Streptococcus intermedius

JOURNAL=Frontiers in Microbiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2020.00826

DOI=10.3389/fmicb.2020.00826

ISSN=1664-302X

ABSTRACT=<p><italic>Streptococcus intermedius</italic> is a β-hemolytic Gram-positive member of the <italic>Streptococcus anginosus</italic> group (SAG). Despite being a part of the normal microbiota, it is one of the most common pathogens associated with brain and liver abscesses and thoracic empyema, increasing as a result the morbidity and mortality rates in affected patients. Though there are numerous published case reports on <italic>S. intermedius</italic> infections, it is still understudied compared to other SAG members. Our knowledge of the genomic factors contributing to its dissemination to the brain and abscess development is also limited to few characterized genes. In this review, we summarize our current knowledge on <italic>S. intermedius</italic> identification methods, virulence factors, and insight provided by the whole-genome and correlate patients’ metadata, symptoms, and disease outcome with <italic>S. intermedius</italic> infections in 101 recent case reports obtained from PubMed. This combined information highlights the gaps in our understanding of <italic>S. intermedius</italic> pathogenesis, suggesting future research directions to unveil the factors contributing to abscess development.</p>