Lemierre's Syndrome Bacteria Are Responsible for Many Cases of Sore Throat Among Adolescents in the US

A recent study conducted at a student health clinic in the United States found that more cases of severe sore throat (pharyngitis) among young adults were caused by the bacterium Fusobacterium necrophorum than by hemolytic streptococci or by Mycoplasma pneumoniae.

The anaerobic bacterium F. necrophorum was shown in European studies to account for about 10% of sore throats and was the primary cause of Lemierre's syndrome.

Lemierre's syndrome develops most often after a sore throat caused by some bacterium of the Streptococcus genus has created a peritonsillar abscess, a pocket filled with pus and bacteria near the tonsils. Deep in the abscess, anaerobic bacteria like F. necrophorum can flourish. The bacteria penetrate from the abscess into the neighboring jugular vein in the neck and there they cause an infected clot to form, from which bacteria are seeded throughout the body by the bloodstream. Bits of the infected clot break off and travel to the lungs as emboli where they block branches of the pulmonary artery bringing deoxygenated blood from the heart to the lungs. This causes shortness of breath, chest pain, and severe pneumonia. The syndrome affects mostly adolescents and young adults and is seen rarely in pre-adolescents. It often causes long, complex hospitalizations requiring intensive care, and although the organism is usually sensitive to penicillin and other antibiotics, about 6% of those contracting Lemierre’s syndrome die.

As there is little available data regarding F. necrophorum infection in the US, investigators at the University of Alabama (Birmingham, USA) used an in-house PCR assay to identify four different pathogenic microorganisms in throat swabs from 312 students aged 15 to 30 years presenting to a student health clinic with an acute sore throat and 180 asymptomatic students.

Results revealed that F. necrophorum was detected in 20.5% of patients and 9.4% of asymptomatic students. Group A beta-hemolytic Streptococcus was detected in 10.3% of patients and 1.1% of asymptomatic students. Group C/G beta-hemolytic Streptococcus was detected in 9.0% of patients and 3.9% of asymptomatic students. Mycoplasma pneumoniae was detected in 1.9% of patients and none of the asymptomatic students.

“This is the first study in the United States that shows that F. necrophorum causes a significant number of cases of pharyngitis in this young adult population,” said first author Dr. Robert M. Centor, professor of general internal medicine at the University of Alabama. “It is also the first to show that F. necrophorum pharyngitis and Streptococcus pharyngitis share similar clinical signs. This study bolsters our understanding that this condition is common in the US and very closely resembles strep throat.”

“It is not just about strep throat in this 15–30 age group,” said Dr. Centor. “Physicians have to consider F. necrophorum, which in our study caused more sore throats than strep. And, F. necrophorum is itself associated with a potentially devastating complication, which while rare, is a more common side effect that acute rheumatic fever. This is the first step in a series of studies that need to be done to define the prevalence and extent of F. necrophorum and how it presents clinically. A very important next step is to develop a practical and affordable point-of-care test for F. necrophorum.”

The study was published in the February 17, 2015, online edition of the journal Annals of Internal Medicine.

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