Risk of mortality in Fusobacterium species bloodstream infection from a large Australian cohort.

BACKGROUND

Fusobacterium species are anaerobic Gram-negative bacilli which are uncommon causes of bloodstream infection (BSI). This genus commonly colonises the gastrointestinal tract and can result in significant morbidity.

METHODS

All blood cultures with growth of Fusobacterium species among residents of Queensland, Australia (population ≈ 5 million) were retrospectively identified over a 20-year period. Clinical, microbiological and outcome information was obtained from state-wide databases.

RESULTS

377 incident Fusobacterium species BSI among 375 individuals for an age and sex-standardised incidence of 4.4 per million residents per year. Median age was 47 years (IQR, 24.9-65.8) and 156 (42%) incident episodes were in females. There was a bimodal frequency distribution with respect to age with peaks occurring around 20 and 65 years, respectively. The most identified source of infection was the abdominal (17%), followed by head and neck (12%). 8% of patients had a septic thrombus present, and 4% had an abscess associated with their BSI. Most isolates were F. nucleatum (142, 38%) and F. necrophorum (140, 37%). 9% of isolates were resistant to penicillin. Older age (aHR 1.02, 95% CI 1.01-1.05), healthcare-associated hospital onset (aHR 3.16, 95% CI 1.35-7.40), and Charlson Comorbidity index (aHR 1.20, 95% CI 1.06-1.35) were all associated with 30-day all cause case-fatality. Oropharyngeal source appeared to be a protective factor (P = 0.02).

CONCLUSIONS

Fusobacterium species BSI results in significant morbidity and can cause death in vulnerable patient groups such as the elderly and those with malignancy. An identifiable oropharyngeal source identifies a favourable host.