Intermedius Streptococcus is a group of Streptococcus (Str. intermedius group), including 3 species, namely, intermedius Streptococcus (Str.intermedius), constellatus Streptococcus (Str.contellatus) and anginosus Streptococcus (Str.anginosus). 93% of intermedius Streptococcus are non-β-hemolytic, 38% of constellatus Streptococcus and 12% of anginosus Streptococcus are β-hemolytic. This group of bacteria mainly exists in the human oral cavity, and can be isolated from gingival crevices, dental plaque, and root canals. It also exists in the throat and nasopharynx, and colonizes in the gastrointestinal tract. This group of bacteria can cause gingival abscesses, and can lead to sepsis and endocarditis. It is worth noting that this group of streptococci can also cause brain abscesses, and often coexist with anaerobic bacteria. Peritonitis, liver abscesses, and pelvic abscesses can also be found. Inhalation of intermedius Streptococcus bacteria in the oropharynx can lead to aspiration pneumonia, which can be complicated by lung abscess and empyema, and there have been reports of mediastinitis. Other infections can also cause osteomyelitis, suppurative arthritis, sinusitis, subcutaneous abscesses, cellulitis, etc.