Fusobacterium & Dichelobacter Flashcards
What is Fusobacterium? How does it respond to antibiotics?
obligate anaerobic, Gram-negative, filamentous rods
(fuso = fusiform = spindle-shaped/spherococoid - pleomorphic)
- sensitive to kanamycin
- resistant to vancomycin
What unique substance does Fusobacterium produce? Where is it commonly found?
butyric acid
normal flora at mucosal sites of the gut, urogenital tract, and oral cavity
What 3 species of Fusobacterium act as opportunistic pathogens?
- F. nucleatum - humans (most common oral pathogen)
- F. canifelium - dogs, cats (bite wounds)
- F. necrophorum - sheep, cattle
Diseases associated with Fusobacterium nucleatum in humans:
What are the 2 subspecies (biotypes) of Fusobacterium necrophorum?
- F. necrophorum subsp. necrophorum (biotype A) - virulent
- F. necrophorum subsp. funduliforme (biotype B) - less virulent
How does Fusobacterium necrophorum affect humans and sheep/cattle?
HUMANS = strain B (necrobacillosis)
- Lemierre’s syndrome: sepsis after bacterial throat infection leading to pain, throat/neck swelling, and respiratory signs
SHEEP/CATTLE = strain A (necrobacillosis)
- calf diphtheria
- liver abscesses
- footrot
- metritis
Fusobacterium necrophorum causes polymicrobial infections. What are 4 other associated pathogens?
- Trueperella pyogenes - G+, facultative anaerobe
- Porphyromonas levii - G-, obligate anaerobe
- Prevotella melaninogenica - G-, obligate anaerobe
- Dichelobacter nodosus - G-, obligate anaerobe
What 3 virulence factors aid in Fusobacterium necrophorum attachment to host cells?
- hemagglutinins
- pili
- outer membrane proteins (FomA)
What 4 toxins act as virulence factors for Fusobacterium necrophorum?
- leukotoxin - lyses leukocytes (neutrophil and macrophage apoptosis)
- LPS - endotoxin
- hemolysin - lyse erythrocytes to impair oxygen transport and create an anaerobic environment
- dermonecrotic toxin - lyse collagen
What 2 media does Fusobacterium necrophorum grow best on?
- blood agar supplemented with hemin and vitamin K1
- Fusobacterium selective agar (FSA)
(in an anaerobic culture)
What molecular analysis is used to confirm a Fusobacterium necrophorum infection?
PCR - IktA gene —> codes for leukotoxin
How are Fusobacterium necrophorum infections treated?
- antibiotic therapy (penicillin G, sulfonamides, metronidazole, ampicillin, florfenicol, ceftiofur)
- surgical intervention to debride infected tissue
What is calf diphtheria? What are the most affected hosts?
ulcerative necrosis of the cheek, tongue, pharynx, and larynx caused by Fusbacterium necrophorum
- AKA: oral necrobacillosis, necrotic pharyngitis or laryngitis
calves under 3 months
What are the 2 forms of calf diphtheria?
- oral form (necrotic stomatitis) - ulceration of the oral mucosa and swelling of the cheek
- laryngeal form (necrotic laryngitis) - ulceration of the larynx
What are 3 symptoms of the oral form of calf diphtheria?
- cheek swelling
- salivation
- tongue ulceration
What are the clinical features of the laryngeal form of calf diphtheria? What 2 things are commonly seen on postmortem examination?
stridor (“roaring”) and difficulty feeding (laryngeal obstruction)
- caseous necrosis
- soft tissue swelling
What are the 5 steps of the pathogenesis of calf diphtheria?
- eating abrasive feeds/tube feeding
- abrasions/trauma
- invasion of Fusobacterium necrophorum
- inflammation
- necrosis, ulceration, and abscesses in oral cavity, pharynx, and larynx
What is expected on a bacterial culture from specimen expected to be infected with Fusobcterium necrophorum?
polymicrobial —> F. necrophorum + Trueperella pyogenes from laryngeal swabs from animals with clinical laryngitis
What are 2 options for calf diphtheria treatment?
- systemic administration of sulfonamides or tetracyclines
- NSAIDs
(early treatment is more effective)
What is the most likely causative agent of liver abscesses in feedlot cattle (and rarely feedlot lambs)?
Fusobacterium necrophorum + Trueperella pyogenes
How does Fusobacterium necrophorum cause liver abscesses?
- high carb diet
- increased SCFA/lactate in the rumen —> acidosis
- F. necrophorum flourishes in the rumen using lactate as an energy source and anchors onto the ruminal wall that maintains a neutral pH
- damage to the ruminal wall by the bacteria allow it to reach the liver via the portal vein
- invasion into the liver results in abscess formation
Clinical signs of Fusobacterium necrophorum liver abscesses are rare. What are 2 possible signs?
- reduced feed intake
- weight loss
(subclinical —> usually detected at the time of slaughter)
What are 3 major ways of preventing Fusobacterium necrophorum liver abscesses? How can it be treated?
- vaccine against leukotoxin
- antibiotics
- nutritional management - decrease carbohydrates to avoid ruminal acidosis
procaine penicillin G, oxytetracycline, ampicillin trihydrate
What is bovine footrot? What are 3 common causative agents?
infectious disease characterized by inflammation of the foot and subsequent lameness
- Fusobacterium necrophorum
- Porphyromonas levii
- Trueperella pyogenes
What are 6 symptoms of bovine footrot?
- lameness
- swelling of the interdigital space
- necrotic lesions with a foul odor in the interdigital space
- loss of appetite
- fever, pain
- chronic arthritis if untreated
What are 3 ways to treat bovine footrot?
- systemic antibiotics
- removal of necrotic tissue with a topical antibiotic
- footbaths containing zinc sulphate
What are common ways that bovine footrot is prevented?
- environmental hygiene (bacteria found in feces)
- good nutrition with vitamin A, D, and zinc
- keeping feet clean and dry
- removal of the sources of foot injuries
- footbaths with antiseptics and astringent solution
What is thrush?
chronic disease in horses by Fusobacterium necrophorum infection in the frog —> hoofrot
What are the 4 clinical signs of thrush (hoofrot)? How is it treated?
- foul smelling discharge in the frog (often black)
- loss of frog shape
- tenderness of the frog
- lameness
debridement, footbaths, antibiotics
- prevented with environmental hygiene and hoof care
What is metritis? What are 4 clinical symptoms?
acute inflammation of the uterus within 21 days postpartum, commonly caused by Fusobacterium necrophorum
- enlarged uterus
- fetid, watery, red-brownish uterine discharge
- fever
- reduced milk production and appetite
How are uterine discharges scored for metritis diagnosis?
1 = clear discharge
2 = cloudy discharge with specks of pus
3 = purulent discharge
4 = bloody, purulent discharge
5 = foul-smelling, brown-red, watery discharge (metritis)
Metritis is commonly a polymicrobial infection. What are the 4 most common etiological agents?
- Fusobacterium necrophorum
- Bacteroides pyogenes
- Porphyromonas levii
- Helcococcus ovis
What are the 3 outcomes of metritis in cows? How is it commonly treated?
- reduced milk production
- reduced reproduction
- increased culling
- significant economic loss
antibiotic treatment: ceftiofu***r, ampicillin, oxytetracycline
What is necrotic rhinitis? What are the most common causative agent and host?
chronic inflammation of the mucous membrane of the nose
Fusobacterium necrophorum
young pigs
What are the 4 clinical signs of necrotic rhinitis? How is it treated?
- necrosis of the snout
- foul-smelling nasal discharge
- face swelling
- sneezing
sulfonamides
Necrotic vs. atrophic rhinitis:
What is Dichelobacter nodosus?
Gram-negative, non-motile, obligate anaerobic rods in the phylum Proteobacteria
What is Dichelobacter nodosus a major cause of?
footrot in sheep and goats (+ Fusobacterium necrophorum)
What 2 virulence factors does Dichelobacter nodosus have?
- type IV fimbriae (fimA)
- production of serine proteases
Where should samples for Dichelobacter nodosus isolation be taken from? What media does it grow best on?
swabs from interdigital skin/lesions and tissue
anaerobic culture in fastidious anaerobe agar containing 10% horse blood > 4 days
(PCR + sequencing)
Fusobacterium and Dichelobacter summary:
Bacteroides, Porphyromonas, and Prevotella are….
a. spore-forming, Gram-positive anaerobes
b. non-spore-forming, Gram-negative anaerobes
B
(A = Clostridium)
Which route is most likely associated with bacteremia caused by anaerobic bacteria?
a. bite wounds
b. ingestion of contaminated water
A - normal flora of the oral cavity of animals
(ingestion —> diarrhea + E. coli)
Which of the following is the most likely to be associated with periodontal disease in dogs?
a. Prevotella
b. Porphyromonas
B
Which of the following virulence factors is involved in abscess formation of anaerobic bacteria?
a. capsule
b. LPS
A - antiphagocytic
(B = endotoxin, septic shock)
This picture shows an abscess fluid smear from a 40 year old man with pyogenic liver abscesses caused by Fusobacterium necrophorum. Which one indicated F. necrosporum?
3 = filamentous G- rods (phagocytized by neitrophils)
Which of the following etiologies of bacterial pharyngitis is not detected by routine aerobic throat cultures?
a. Fusobacterium necrosporum
b. Streptococcus pyogenes
c. Trueperella pyogenes
A - obligate anaerobe
What are the diseases associated with Fusobacterium necrophorum in cattle?
(necrobacillosis)
- calf diphtheria (<3 months)
- liver abscesses (feedlot cattle with high carb diets)
- metritis (postpartum dairy cows)
- footrot (lameness in beef cattle)
A sheep showed lameness and necrotic lesions with a foul odor in the interdigital space. What microorganism is most likely responsible for these symptoms?
Dichelobacter nodosus
(+ Fusobacterium necrophorum as a secondary invader)
What is chicken foot disease called? What microorganisms are likely responsible for these foot infections?
- Bumblefoot (pododermatitis)
- Staphylococcus aureus
- E. coli
- Pseudomonas
