Streptococcus intermedius (S. intermedius) (S. intermedius)

Streptococcus intermedius is a Gram-positive, facultative anaerobic bacterium and a member of the Streptococcus anginosus group (SAG), also known as the Streptococcus milleri group (StatPearls, 2023). While it is a common commensal of the human oral cavity and gastrointestinal tract, it is a significant opportunistic pathogen uniquely associated with the formation of deep-seated purulent abscesses, particularly in the brain and liver (NCBI, 2023). A key virulence factor of S. intermedius is the production of Intermedilysin (ILY), a human-specific cholesterol-dependent cytolysin that binds to the human complement regulatory protein CD59 to cause cell lysis (Journal of Bacteriology, 2003). In clinical practice, S. intermedius is not a molecular target itself but is the pathogen targeted by antimicrobial therapy. Treatment typically involves long-term administration of beta-lactam antibiotics such as penicillin or ceftriaxone, which inhibit bacterial cell wall synthesis, often in conjunction with surgical drainage of abscesses (PubMed, 2022). The organism's ability to thrive in low-oxygen environments and its synergy with other anaerobic bacteria make it a significant challenge in infectious disease management.

Other names

Streptococcus milleriStreptococcus anginosus group memberS. intermedius

Antibiotics targeting Streptococcus intermedius primarily function by inhibiting bacterial cell wall synthesis through the binding of penicillin-binding proteins (e.g., beta-lactams), inhibiting protein synthesis via the 50S ribosomal subunit (e.g., clindamycin), or disrupting DNA gyrase and topoisomerase IV (e.g., fluoroquinolones).