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Fusobacterium and Tonsillar Infections
Abstract & Commentary
By Dean L. Winslow, MD, FACP, FIDSA, Chief, Division of AIDS Medicine, Santa Clara Valley Medical Center; Clinical Professor, Stanford University School of Medicine, is Associate Editor for Infectious Disease Alert.
Dr. Winslow serves as a consultant for Siemens Diagnostics and is on the speaker's bureau for GSK and Cubist.
Synopsis: Eight hundred and forty-seven patients with peritonsillar abscess (PTA) admitted to Aarhus University hospitals from 2001-2006 were included in this retrospective study. Fusobacterium necrophorum (FN) was the most frequently detected bacterium (23%), followed by group A streptococci (GAS) (17%) and groups C and G streptococci (GCS/GGS) (5% combined).
Source: Ehlers T, et al. Fusobacterium necrophorum: Most prevalent pathogen in peritonsillar abscess in Denmark. Clin Infect Dis. 2009;49:1467-1472.
Eight hundred and forty-seven patients with peritonsillar abscess admitted to the ENT service at Aarhus University hospitals from 2001-2006 were included in this retrospective study. Most patients underwent tonsillectomy and/or incision and drainage. Pus aspirates and pus swab samples were cultured for routine and anaerobic cultures using standard microbiological methods.
The median age of patients studied was 21 years. FN alone was isolated from 167 patients, GAS alone from 133, GCS/GGS alone from 23, FN plus beta hemolytic strep from 24, other bacteria 58, mixed oral flora from 355, no culture was obtained in 87 patients, and a diagnosis of infectious mononucleosis was made in 26 patients.
Of the 760 patients who had cultures taken, FN was recovered from 44% of those patients with PTA who received antibiotics prior to admission and from 36% of those patients who had not received antibiotics.
The information in this paper is quite interesting. The increased isolation of FN from patients with PTA in this study vs. the relatively low prevalence of this organism in historical literature may reflect the use of better anaerobic bacteriology in the clinical setting at this institution. Brook et al, in an earlier study, found other anaerobes, including Prevotella, Porphyromonas, and Peptostreptococcus, as well as Fusobacterium in PTA and parapharyngeal abscesses.1
The big concern about FN is its association with Lemierre's syndrome (septic thrombophlebitis of the internal jugular vein following sore throat). Interestingly, the authors of this study do not comment on whether or not they saw Lemierre's in any of their patients. Late last year, there was a somewhat alarming "Perspective" article published in Annals of Internal Medicine recommending that we should stop focusing solely on GAS and "expand the pharyngitis paradigm for adolescents and young adults."2 This recommendation was made by the author based on several case reports of FN causing (or at least being isolated from patients with) pharyngitis. His recommendation to use penicillin derivatives, and to avoid macrolides, in the treatment of GAS-negative pharyngotonsillitis seemed somewhat illogical since the concern about using macrolides would seem to be related to the increased prevalence of macrolide resistance in GAS. Also, if the recommendation to always use β-lactam agents empirically for the treatment of adolescents with pharyngotonsillitis is to prevent complications of FN infection, the results of the Danish study do not support that, since penicillins were administered to 94% of the 293 antibiotic-treated patients with PTA, if anything appeared to increase the risk for isolation of FN.
Despite the frequent isolation of FN from patients undergoing tonsillectomy or incision and drainage for PTA, Lemierre's syndrome fortunately seems to be a rare complication (I have cared for only three patients with Lemierre's in my 37-year career). While FN is clearly an important pathogen capable of causing both PTA and Lemierre's syndrome, its overall importance as a cause of all cases of pharyngotonsillitis remains uncertain. In another recently published study, throat swabs were taken from 411 mostly asymptomatic university students and from 103 patients who presented with sore throat.3 The throat swabs were tested for β-hemolytic streptococci by routine culture and for EBV and F. necrophorum DNA by PCR. FN was found in 43 of 411 (10.5%) students, and this represented asymptomatic carriage in 29 of 43 (67.4%).
It is difficult to integrate all of these findings into a coherent story. Clearly, FN is a pathogen capable of causing both peritonsillar abscess (commonly) and Lemierre's syndrome (rarely). However, FN is also commonly isolated from the throats of asymptomatic adolescents and young adults. I generally prescribe antimicrobials for patients with clinically significant tonsillitis whether or not GAS is present on rapid screen or culture. Due to the common presence of FN in asymptomatic and minimally symptomatic younger patients, I am not convinced that it makes sense to routinely test patients with just pharyngitis/mild tonsillitis for the presence of FN, nor should empiric therapy be given for this organism in all cases.