Fusobacterium necrophorum as the cause of recurrent sore throat: comparison of isolates from persistent sore throat syndrome and Lemierre's disease.

OBJECTIVE: Fusobacterium necrophorum is a well established cause of Lemierre's disease (LD); a syndrome characterised by severe sore throat, septicaemia, multiple abscesses and jugular vein thrombosis. There is no published data concerning the role of F. necrophorum in recurrent sore throats. As the result of an index case of persistent sore throat attributable to this organism being diagnosed in our laboratory, a subsequent case controlled study (not yet published) isolated F. necrophorum from 21% (P=0.0001) of cases of persistent, recurrent and chronic sore throats. The object of this study was to compare isolates of F. necrophorum from cases of systemic disease with isolates from cases of persistent sore throat syndrome (PSTS) to ascertain whether strains of similar type were responsible for both throat and systemic disease or whether different strains were involved in these presentations.

METHODS: Throat swabs were cultured on GN anaerobe medium (Oxoid) and incubated at 37 degrees C for 5 days. Seventeen PSTS isolates were identified phenotypically. These were compared to 17 strains isolated from blood cultures which were referred to the Anaerobe Reference Unit, (ARU) cardiff, using enterogenic repetitive intergenic consensus-polymerase chain reaction (ERIC-PCR). The control strains Fusobacterium necrophorum ssp. necrophorum (JCM 3718(T)) and Fusobacterium necrophorum ssp. funduliforme (JCM 3724(T)) from the Japanese Collection of Microrganisms (JCM) were tested in parallel with the clinical isolates.

RESULTS: At least 12 separate types were identified. Four of 17 PSTS isolates and seven of 17 blood culture isolates grouped together with the F. necrophorum ssp. funduliforme control strain. There were also similarities between other proposed strains and clinical types but no comparison with the F. necrophorum ssp. necrophorum control.

CONCLUSION: These results show that clinical disease caused by F. necrophorum has a wider spectrum than first anticipated. Similar strains are able to cause either chronic local or acute systemic disease suggesting that genetic factors such as those relating to major histocompatibility complex (MHC) class may be influencing the outcome of the disease in each patient. Further work is required to produce a more accurate typing scheme and to ascertain the mechanisms of disease caused by this organism. An age correlation between the high risk groups for onset of infectious mononucleosis (IM), peritonsillar abscess (PTA), LD and PSTS has been noted in adolescents and young adults. Further work is required to investigate whether IM is associated with the onset of PTA caused by F. necrophorum which may lead to either PSTS or LD.