Lemierre's disease, an oropharyngeal infection is MOST COMMONLY caused by which of the following organisms?

Postanginal septicemia or Lemierre's disease is a rare anaerobic oropharyngeal infection caused predominantly by F. necrophorum. It is commonly seen in young adults and they present as exudative tonsillitis or peritonsillar abscess. This infection can spread to lateral pharyngeal space, which contains the carotid aery and internal jugular vein. Patients are usually treated with IV antibiotics (penicillin G or clindamycin) and surgical drainage of any purulent collections if present is done.