PCR shows there is more than meets the eye in some sore throats

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PCR shows there is more than meets the eye in some sore throats

If you go to the doctor with pharyngitis, you will most probably be told that it’s “just a sore throat“, and more often than not it is – a simple strep throat, or perhaps a viral infection. However, studies using the polymerase chain reaction (PCR) have shown that Fusobacterium necrophorum is more often the cause than streptococcus of a severe sore throat that worsens in young adults. The research, from the University of Alabama at Birmingham, was published in Annals of Internal Medicine.

Strep throat

Source: James Heilman, MD

The researchers looked at 312 students aged 15 to 30 years who attended a student health clinic with an acute sore throat, and compared them with 180 asymptomatic students. The students were tested for F necrophorum, Mycoplasma pneumoniae, and group A and C/G ?-haemolytic streptococcal pharyngitis, using PCR tests from throat swabs, and their signs and symptoms recorded to calculate a Centor score.

F necrophorum pharyngitis is hard to recognize, with very similar signs and symptoms to those of strep throat. However, F necrophorum pharyngitis is the leading cause of a rare but potentially very dangerous condition known as Lemierre’s syndrome, which is sometimes referred to as the forgotten disease. This is a serious infection, causing an infected abscess on the tonsils that can lead to an infected thrombosis that seeds infection throughout the body, and pneumonia if emboli travel to the lungs. It affects mostly adolescents and young adults, and is seen in around one in 70,000 adolescents/young adults each year. It often causes long, complex hospitalizations requiring intensive care. The mortality rate is 4-12%. Lemierre’s syndrome has been making a comeback in the past 10 years as antibiotic use has slowed due to fears of antibiotic resistance.

The challenge for doctors is that the symptoms of F necrophorum pharyngitis are similar to those of a severe strep throat, and while there is a rapid test for strep, there is no a routine, commercially available rapid test for F necrophorum.

“It is not just about strep throat in this 15-30 age group. Physicians have to consider F necrophorum, which in our study caused more sore throats than strep. For an infection caused by F necrophorum, aggressive therapy with antibiotics is appropriate, as the bacterium responds well to penicillin and other antibiotics,” said Robert M Centor, professor in the Division of General Internal Medicine in the UAB School of Medicine. “We suspect that many physicians would prescribe antibiotics for patients with F necrophorum pharyngitis if there were a point-of-care diagnostic test that proved its presence.”

The PCR test results were:

  • F necrophorum – 20.5% of patients and 9.4% of asymptomatic students
  • Group A ?-haemolytic streptococcus – 10.3% of patients and 1.1% of asymptomatic students
  • Group C/G ?-haemolytic streptococcus – 9.0% of patients and 3.9% of asymptomatic students
  • M pneumoniae – 1.9% of patients and 0 asymptomatic students.

In the student population, infection with F necrophorum in severe sore throats is around twice as common as either group A ?-haemolytic streptococcus or group C/G ?-haemolytic streptococcus. Those with higher Centor scores were more likely to be infected with F necrophorum, group A streptococcus, or group C/G streptococcus increased (P < 0.001). Clinically, F necrophorum-positive pharyngitis was similar to streptococcal pharyngitis.

“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,” says Centor. “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.”

“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,” Centor said. “A very important next step is to develop a practical and affordable point-of-care test for F necrophorum.”

While xxpress PCR technology wasn’t used for this project, the system’s fast turnaround of results, convenient size and high accuracy means that it has potential for near patient testing.

The xxcloud is our exciting new software release, enabling users to programme and analyse results remotely, from a PC or laptop.

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