The aetiology of pharyngotonsillitis in adolescents and adults – Fusobacterium necrophorum is commonly found

Sore throat is common in primary healthcare. Aetiological studies have focused on the presence of a limited number of pathogens. The aim of the present study was to investigate the presence of a wide range of bacteria and viruses, including Fusobacterium necrophorum, in patients with pharyngotonsillitis and in asymptomatic controls. A prospective case control study was performed in primary healthcare in Kronoberg County, Sweden. Patients (n = 220) aged 15 to 45 years with a suspected acute pharyngotonsillitis, and controls (n = 128), were included. Nasopharyngeal and throat swabs were analysed for β-hemolytic streptococci, F. necrophorum, Mycoplasma pneumoniae, and Chlamydophila pneumoniae, and 13 respiratory viruses. Serum samples were analysed for antibodies to Epstein-Barr virus. The patient history and symptoms, including Centor score, were analysed in relation to pathogens. In 155/220 (70.5%) of the patients, as compared to 26/128 (20.3%) of the controls (p <0.001), at least one microorganism was found. Group A streptococci, F. necrophorum, and influenza B virus were the three most common findings, and all significantly more common in patients than in controls (p <0.001, p 0.001, and p 0.002, respectively). Patients with F. necrophorum only (n = 14) displayed a lower Centor score than patients with Group A streptococcus only (n = 46), but a higher score than patients with influenza B, other viruses, or no potential pathogen (Kruskal-Wallis p <0.001). A pathogen was detected in 70% of the patients, displaying a wide range of pathogens contributing to the aetiology of pharyngotonsillitis. This study supports F. necrophorum as one of the pathogens to be considered in the aetiology of pharyngotonsillitis.