Lemierre’s disease, an oropharyngeal infection is MOST COMMONLY caused by which of the following organisms?
**Core Concept**
Lemierre's disease is a rare but serious post-infectious complication of oropharyngeal infections, characterized by severe neck pain, fever, and a distinct clinical presentation. It is caused by a bacterial infection that leads to the formation of a septic internal jugular vein thrombophlebitis.
**Why the Correct Answer is Right**
The correct answer is **Fusobacterium necrophorum**, a gram-negative, anaerobic bacterium that is a common inhabitant of the human oral cavity. In Lemierre's disease, F. necrophorum is thought to invade the oropharyngeal tissues and then migrate to the jugular vein, where it causes a septic thrombophlebitis. This infection can lead to severe complications, including sepsis, endocarditis, and meningitis. The bacterium produces enzymes that help it to invade and colonize host tissues, leading to tissue damage and the characteristic clinical presentation of Lemierre's disease.
**Why Each Wrong Option is Incorrect**
* **Option A:** *Streptococcus pyogenes* is a gram-positive bacterium that is more commonly associated with pharyngitis and skin infections, rather than Lemierre's disease.
* **Option B:** *Haemophilus influenzae* is a gram-negative bacterium that can cause respiratory tract infections, but is not typically associated with Lemierre's disease.
* **Option D:** *Staphylococcus aureus* is a gram-positive bacterium that can cause a wide range of infections, but is not commonly associated with Lemierre's disease.
**Clinical Pearl / High-Yield Fact**
Lemierre's disease is often misdiagnosed as a case of pharyngitis or tonsillitis, but it requires prompt recognition and treatment to prevent severe complications. The characteristic clinical presentation includes severe neck pain, fever, and a distinct "jugular venous distension" sign.
**Correct Answer: C. Fusobacterium necrophorum**