Analysis of the tonsillar microbiome in young adults with sore throat reveals a high relative abundance of Fusobacterium necrophorum with low diversity.

Fusobacterium necrophorum (Fn), a gram-negative anaerobe, is increasingly implicated as an etiologic agent in older adolescents and young adults with sore throat. Inadequately treated Fn pharyngitis may result in suppurative complications such as peritonsillar abscess and Lemierre's syndrome. Data from the literature suggest that the incidence of life-threating complications in these age groups from Fn pharyngitis (Lemierre's syndrome) in the United States exceeds those associated with group A beta-hemolytic streptococcal (GAS) pharyngitis (acute rheumatic fever). Using real-time PCR, we previously reported about a 10% prevalence of Fn in asymptomatic medical students and about 20% in students complaining of sore throat at a university student health clinic (p = 0.009). In this study, a comprehensive microbiome analysis of the same study samples confirms that Fn pharyngitis was more common than GAS pharyngitis. Eighteen patients were found to have Fn OTU values exceeding an arbitrary cutoff value of 0.1, i.e. greater than 10% of total sequences, with five subjects reaching values above 0.7. By contrast only 9 patients had GAS OTU values greater than 0.1 and none exceeded 0.6. When the data were analyzed using five separate assessments of alpha diversity, in each case for Fn there were statistically significant differences between Fn positive_high (OTU abundance > 0.1) vs control, Fn positive_high vs Fn negative (OTU abundance = 0), Fn positive_high vs Fn positive_low (OTU abundance > 0 and < 0.1). When the data were analyzed using three beta diversity indexes (Bray-Curtis, weighted unifrac, and unweighted unifrac), there were statistically significant differences between Fn positive_high (OTU abundance ≥ 0.1) vs control for all three. Statistically significant differences remained if we chose somewhat different OTU abundance cutoffs of 0.05 or 0.15. We conclude that Fn appears to play a dominant role in bacterial pharyngitis in the older adolescent and young adult age groups and that the development of a productive mucosal infection with Fn is linked to a significant decrease in the diversity of the associated tonsillar microbiome.

The clinical presentation of Fusobacterium-positive and streptococcal-positive pharyngitis in a university health clinic: a cross-sectional study.

BACKGROUND: Pharyngitis guidelines focus solely on group A ß-hemolytic streptococcal infection. European data suggest that in patients aged 15 to 30 years, Fusobacterium necrophorum causes at least 10% of cases of pharyngitis; however, few U.S. data exist. OBJECTIVE: To estimate the prevalence of F. necrophorum; Mycoplasma pneumoniae; and group A and C/G ß-hemolytic streptococcal pharyngitis and to determine whether F. necrophorum pharyngitis clinically resembles group A ß-hemolytic streptococcal pharyngitis. DESIGN: Cross-sectional. SETTING: University student health clinic. PATIENTS: 312 students aged 15 to 30 years presenting to a student health clinic with an acute sore throat and 180 asymptomatic students. MEASUREMENTS: Polymerase chain reaction testing from throat swabs to detect 4 species of bacteria and signs and symptoms used to calculate the Centor score. RESULTS: Fusobacterium necrophorum was detected in 20.5% of patients and 9.4% of asymptomatic students. Group A ß-hemolytic streptococcus was detected in 10.3% of patients and 1.1% of asymptomatic students. Group C/G ß-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 0 asymptomatic students. Infection rates with F. necrophorum, group A streptococcus, and group C/G streptococcus increased with higher Centor scores (P < 0.001). LIMITATIONS: The study focused on a limited age group and took place at a single institution. Asymptomatic students-rather than seasonal control participants-and a convenience sample were used. CONCLUSION: Fusobacterium necrophorum-positive pharyngitis occurs more frequently than group A ß-hemolytic streptococcal-positive pharyngitis in a student population, and F. necrophorum-positive pharyngitis clinically resembles streptococcal pharyngitis. PRIMARY FUNDING SOURCE: University of Alabama at Birmingham and the Justin E. Rodgers Foundation.