Fusobacterium necrophorum: most prevalent pathogen in peritonsillar abscess in Denmark.

BACKGROUND Group A streptococci are commonly regarded as the most prevalent cause of acute bacterial tonsillitis and peritonsillar abscess (PTA). However, the majority of PTA aspirates also contain strains of anaerobes, and accumulating evidence indicates that Fusobacterium necrophorum (FN) could be involved in acute tonsillitis. The purpose of the present study was to describe the epidemiology and bacteriology of PTA in Denmark, with particular emphasis on correlations between microbiological, clinical, and laboratory data. METHODS A retrospective study on all patients with PTA admitted to the ear, nose, and throat department at Aarhus University Hospitals from January 2001 through December 2006 was conducted. RESULTS In total, 847 patients were included in the study. The mean annual incidence of PTA was 41 cases/100,000 population. FN was the most frequently detected bacteria (in 23% of cultures), followed by group A streptococci (in 17%) and groups C and G streptococci (counted together, in 5%). Of the 191 FN isolates detected, 155 (81%) grew as pure culture. Patients infected with FN were significantly younger than patients infected with other strains of bacteria (P < .001). Patients with FN exhibited significantly higher neutrophil counts (P < .001) and C-reactive protein values (P = .01) than did patients infected with other bacteria. CONCLUSIONS To our knowledge, this study is the first report of FN being the most prevalent pathogen in PTA patients. The significantly higher neutrophil counts and C-reactive protein values strongly indicate the pathogenic importance of FN in PTA. The widespread reliance on rapid streptococcal antigen test in general practice to appoint patients for antibiotics and the highest PTA incidence ever reported raise concern that highly virulent bacteria may be left initially untreated.