NAME: Fusobacterium spp.
SYNONYM OR CROSS REFERENCE: Pathogenic species in the genus Fusobacterium include: F. necrophorum, F.nucleatum, F. canifelinum, F. gonidiaformans, F. mortiferum, F. naviforme, F. necrogenes, F. russii, F.ulcerans, F. varium (1). Taxa formerly in the genus Fusobacterium include: Filifactor alocis, Faecalibacterium prausnitzii, Eubacterium sulci.
Even though it is not found in the natural flora of the human gastrointestinal tract F. canifelinum can cause infections in humans when transferred by dog bites (2)
CHARACTERISTICS: Fusobacterium are anaerobic gram-negative bacilli, non-sporulating, slender cells with tapered ends or pleomorphism (3). They exhibit irregular staining.
PATHOGENICITY/TOXICITY: Fusobacterium spp., are part of the normal flora of the oropharyngeal, gastrointestinal and genital tracts (3). Infections may occur after surgical or accidental trauma, edema, anoxia, tissue destruction, and animal bites (3).
F. necrophorum is the most virulent species and may cause severe infections in children and young adults (i.e. pharyngotonsillitis) (3). It is commonly isolated from peritonsillar abscesses. It is also associated with Lemierre disease, which presents as acute jugular vein septic thrombophlebitis, often with complications including sepsis, and metastastic abscesses in the lungs, liver, joints and pleural spaces. Fusobacteria are encountered in intra-abdominal and pulmonary infections, as well as infections resulting from animal bites.
EPIDEMIOLOGY: Worldwide distribution. Infections are infrequent, and reporting is not consistent (4). F. nucleatum is the most common source of infection, while F. necrophorum is the most virulent species (3). The highest reported prevalence of infection by Fusobacterium was in Denmark where 6.24 cases/1,000,000 population/year during 1998-2001, although worldwide reports range from 0.6 to 6.24 cases /1,000,000 population /year (4). Higher incidences of 14.4 cases/1,000,000 population were observed in Demark for subjects aged 15-24 years.
HOST RANGE: Humans and animals, including horses, cattle, sheep, goats, pigs, fowl (5).
INFECTIOUS DOSE: Unknown
INCUBATION PERIOD: Not clearly defined. Incubation period has not been studied as Fusobacteria are part of the normal flora of humans.
ZOONOSIS: Yes - Fusobacterium can be passed to humans from animal bites or handling of animals with open sore (3).
DRUG SUSCEPTIBILITY: Treatment of Fusobacterium infections depend on the site of infections. Metronidazole, piperacillin/tazobactum, ticarcillin/clavulanate, amoxicillin/sulbactum, ampicillin/sulbactum, ertupenem, imipenem, meropenem, clindamycin, and cefoxitin are all used therapeutically to treat infections associated with Fusobacterium (6, 10)
SUSCEPTIBILITY TO DISINFECTANTS: Fusobacteria are susceptible to solutions of 1% sodium hypochlorite, 0.2% chlorhexidine, 70% ethanol, 2% glutaraldehyde, 3% hydrogen peroxide, formaldehyde, phenolics, iodophores, calcium hydroxide, formocresol, and triclosan (3, 11-13).
The minimum bactericidal concentration is 1562.5μg/ml for calcium hydroxide, 62500.0μg/ml for ethanol, and 1480.0μg/ml for formocresol (11).
PHYSICAL INACTIVATION: Fusobacterium can be inactivated by UV light with a wavelength 254nm (14). Fusobacterium is also susceptible to moist heat of 121°C for at least 15 minutes and dry heat of 170°C for at least 1 hour (15).
SURVIVAL OUTSIDE HOST: Fusobacteria have been known to persist in soil for up to 18 weeks (16). They survive well in wet soil with high manure content (17), however, studies of aerated fecal slurry showed that the levels of Fusobacterium were below the level of detection after 24 hours (18). In non-aerated fecal slurry, no change in Fusobacterium levels were observed in the first 24 hours, and Fusobacteria were no longer present after 6 days. Survival on BHIA medium exposed to air ranges from six hours to seven days depending on species (19).
Note: All diagnostic methods are not necessarily available in all countries.
FIRST AID/TREATMENT: Surgical drainage and/or treatment with appropriate antibiotics (6). If infection is discovered to be caused by F. nucleatum or F. necrophorum, treatment should be started promptly as these two species have been linked to deaths as a result of severe cases of Lemierre’s disease.
PROPHYLAXIS: None know for humans, although increased use of antimicrobials may be associated with reduced reports of infections with Fusobacterium spp. (3). Antimicrobials are used in cattle to reduce the risk of Fusobacteria-associated liver abscesses (21). The antimicrobials most commonly used for animal prophylaxis are bacitracin, methylene disalicylate, chlortetracycline, oxytetracycline, tylosin, and virginiamycin.
LABORATORY-ACQUIRED INFECTIONS: One case of a laboratory acquired infection with Fusobacterium fusiforme has been reported as of 1976 (9).
PRIMARY HAZARDS: Accidental parenteral inoculation and direct contact of mucous membranes constitute the primary hazards when dealing with Fusobacterium spp in the laboratory (7).
SPECIAL HAZARDS: None
RISK GROUP CLASSIFICATION: Risk Group 2 (24). This risk group applies to the genus as a whole, but does not necessarily reflect the risk group classification of every species within the genus.
CONTAINMENT REQUIREMENTS: Containment Level 2 facilities, equipment, and operational practices for work involving infectious or potentially infectious materials, animals, cultures. These containment requirements apply to the genus as a whole, and may not apply to each species within the genus.
PROTECTIVE CLOTHING: Lab coat. Gloves when direct skin contact with infected materials or animals is unavoidable. The use of needles, syringes, and other sharp objects should be strictly limited. Additional precautions should be considered with work involving animals or large scale activities (25).
OTHER PRECAUTIONS: All procedures that may produce aerosols, or involve high concentrations or large volumes should be conducted in a biological safety cabinet (BSC) (25). Additional precautions should be considered with work involving animals or large scale activities (25).
SPILLS: Allow aerosols to settle and, wearing protective clothing, gently cover spill with paper towels and apply suitable disinfectant starting at the perimeter and working towards the centre. Allow sufficient contact time before clean up (25).
DISPOSAL: Decontamination using steam sterilization, chemical disinfection, or incineration must be performed before disposal of infectious waste (25).
STORAGE: All infectious materials should be stored in sealed containers bearing the appropriate labelling (25).
REGULATORY INFORMATION: The import, transport, and use of pathogens in Canada is regulated under many regulatory bodies, including the Public Health Agency of Canada, Health Canada, Canadian Food Inspection Agency, Environment Canada, and Transport Canada. Users are responsible for ensuring they are compliant with all relevant acts, regulations, guidelines, and standards.
UPDATED: July, 2010
PREPARED BY: Pathogen Regulation Directorate, Public Health Agency of Canada.
Although the information, opinions and recommendations contained in this Pathogen Safety Data Sheet are compiled from sources believed to be reliable, we accept no responsibility for the accuracy, sufficiency, or reliability or for any loss or injury resulting from the use of the information. Newly discovered hazards are frequent and this information may not be completely up to date.
Public Health Agency of Canada, 2010