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Should we look out for necrobacillosis?

Q - We have had reports of Fusobacterium necrophorum from throat swabs. The microbiologist said it was a cause of recurrent sore throat and only needs three weeks of penicillin V, but if untreated may cause septicaemia. How serious is it and how likely to cause complications? Should we send swabs and should it always be treated?

A - F.necrophorum, part of the anaerobic normal throat flora, has a predisposition to abscess formation resulting in 'necrobacillosis'.

Necrobacillosis is rare, affecting one per million in the population.

Virulent toxin production and platelet aggregation causes internal jugular venous thrombosis (Lemierre's syndrome). Septic embolisation produces cavitating pulmonary lesions and haemoptysis. Empyemas form in 15 per cent, the pus smelling of Camembert. Septic arthritis, liver, spleen, and muscle abscesses have been described.

Detecting fusobacterial colonisation is impossible. It is prudent to culture a severe sore throat.

I would treat fusobacteria

if isolated, and alert the clinician to look out for any deterioration.

Since some strains are

?-lactamase producers, relapse of symptoms with penicillin is unsurprising. There may be advantages in prescribing a

?-lactamase inhibitor such as co-amoxiclav, as erythromycin is ineffective in up to 22 per cent of cases.

It is often suspected only when blood cultures are positive, so mistreatment as staphylococcal sepsis is common. Rapidly progressive cavitation not responding to anti-staphylococcal antibiotics should provide a clue.

When the true diagnosis is evident, prompt treatment with massive doses of clindamycin, penicillin and metronidazole is lifesaving.

Marina Morgan is consultant medical microbiologist at the

Royal Devon and Exeter Hospital

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