Sore throat more apt to be Fusobacterium than strep in young people

By Megan Brooks

NEW YORK (Reuters Health) - The cause of pharyngitis in U.S. adolescents and young adults is more apt to be Fusobacterium necrophorum than group A beta-hemolytic streptococcus, according to data from a university student health clinic.

"For years, I have personally wondered when a person looks like they have strep and they don't have strep, what do they have? This study answers part of that question," first author Dr. Robert Centor from University of Alabama at Birmingham noted in an interview with Reuters Health.

"Fusobacterium is an anaerobic bacterium, so routine throat culture will not pick it up. We've known for a while from European studies that Fusobacterium necrophorum can cause pharyngitis but nobody had previously determined what it looks like compared to strep. We found, in adolescents and young adults at least, that Fusobacterium pharyngitis looks just like strep pharyngitis and explains a lot of the people that we might want to give antibiotics to but have a negative strep test," Dr. Centor said.

He and his colleagues studied 312 students aged 15 to 30 years with an acute sore throat and 180 asymptomatic students from the UAB student health clinic.

They developed a research polymerase chain reaction (PCR) assay to detect F. necrophorum from throat swabs (and used existing PCR assays to test for M. pneumoniae and groups A, C and G beta-hemolytic streptococci).

The team obtained clinical information including history of fever; presence of cough; swollen, tender cervical lymphadenopathy; and tonsillar exudates to calculate the Centor score, which Dr. Centor developed back in the early 1980s.

According to their February 16 online report in Annals of Internal Medicine, F. necrophorum was detected in 20.5% of patients with sore throat and 9.4% of asymptomatic patients, and was the most common bacterial agent of pharyngitis.

Group A streptococcus was detected in 10.3% of patients and 1.1% of asymptomatic students; group C or G streptococcus was detected in 9.0% of patients and 3.9% of asymptomatic students; and M. pneumoniae was detected in 1.9% of patients and no asymptomatic student.

The researchers say their findings mirror those of recent European studies that suggest F. necrophorum is responsible for at least 10% of pharyngitis cases in adolescents and adults.

They say the clinical presentation of F. necrophorum pharyngitis resembled that of group A streptococcal pharyngitis.

Rates of infection with F. necrophorum, group A, C and G streptococcus increased with higher Centor scores (p<0.001). Among patients with a Centor score of 2 or higher, the probability of strep or F. necrophorum pharyngitis reached the 40% range; with a score of 4 the probability was greater than 70% for having one of these bacteria.

"These results support the Centor score as a predictor of bacterial pharyngitis caused by F. necrophorum as well as non-group A streptococcus rather than just group A streptococcal pharyngitis," the researchers say.

Currently there is no commercially available rapid test for F. necrophorum. "We are hoping that this study will convince someone to develop a rapid test for Fusobacterium," Dr. Centor said.

As for treatment, current U.S. guidelines support antibiotic therapy for known group A streptococcal pharyngitis. However, no guidelines address management of non-group A streptococcal or F. necrophorum pharyngitis.

"Should we be treating these people? There is an honest debate going on," Dr. Centor said. "I think we should because Fusobacterium can have significant complications. It is the major cause of peritonsillar abscess in this age group and it can cause the Lemierre syndrome, which is a devastating complication. If it were my child, I'd probably give them amoxicillin."

Dr. Centor said he favors treating patients with a Centor score of 3 and 4 empirically with a penicillin or cephalosporin. "Clearly, if you are going to treat empirically, you should not use a macrolide; that means don't use a Z-Pak (azithromycin) because it doesn't cover Fusobacterium and there is increasing resistance with strep," he explained.

Dr. Centor emphasized that the findings in this study do not pertain to preadolescents because "they don't seem to get Fusobacterium infection."

In a linked editorial, Dr. Jeffrey Linder from Brigham and Women's Hospital and Harvard Medical School in Boston, Massachusetts, says these new data are "interesting, but do not warrant reconsideration of pharyngitis guidelines."

"(F)rom an empiric standpoint, there is no evidence that treating F. necrophorum pharyngitis with antibiotics decreases symptoms or prevents Lemierre's disease. To be clear, Lemierre's disease can be catastrophic. F. necrophorum, Lemierre's syndrome, and other causes of pharyngitis demand attention and physicians need to avoid 'undercomplicating' complicated pharyngitis. In particular, physicians should broaden their differential diagnosis and consider additional testing for patients who have 3 or 4 Centor criteria, have a negative rapid test for GAS, and fail to improve or patients who are not improving within 24 to 36 hours of antibiotic treatment," Dr. Linder writes.

"However, the major quality problem in sore throat management remains that physicians overcomplicate uncomplicated pharyngitis. Physicians and practices should remember the prevalence of GAS in adults with sore throat is about 10%, use the Centor Criteria, selectively use rapid antigen detection testing, limit antibiotic treatment to patients most likely to have GAS, and, most of the time when prescribing antibiotics, use penicillin," Dr. Linder advises.

The study had no commercial funding and the authors have no disclosures.

SOURCE: http://bit.ly/1L0bpVb

Ann Intern Med 2015.

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