Veterinary Bacteriology & Mycology > Fusobacterium & Dichelobacter > Flashcards

Fusobacterium & Dichelobacter Flashcards

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1
Q

What is Fusobacterium? How does it respond to antibiotics?

A

obligate anaerobic, Gram-negative, filamentous rods
(fuso = fusiform = spindle-shaped/spherococoid - pleomorphic)

  • sensitive to kanamycin
  • resistant to vancomycin
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2
Q

What unique substance does Fusobacterium produce? Where is it commonly found?

A

butyric acid

normal flora at mucosal sites of the gut, urogenital tract, and oral cavity

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3
Q

What 3 species of Fusobacterium act as opportunistic pathogens?

A
  1. F. nucleatum - humans (most common oral pathogen)
  2. F. canifelium - dogs, cats (bite wounds)
  3. F. necrophorum - sheep, cattle
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4
Q

Diseases associated with Fusobacterium nucleatum in humans:

A
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5
Q

What are the 2 subspecies (biotypes) of Fusobacterium necrophorum?

A
  1. F. necrophorum subsp. necrophorum (biotype A) - virulent
  2. F. necrophorum subsp. funduliforme (biotype B) - less virulent
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6
Q

How does Fusobacterium necrophorum affect humans and sheep/cattle?

A

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

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7
Q

Fusobacterium necrophorum causes polymicrobial infections. What are 4 other associated pathogens?

A
  1. Trueperella pyogenes - G+, facultative anaerobe
  2. Porphyromonas levii - G-, obligate anaerobe
  3. Prevotella melaninogenica - G-, obligate anaerobe
  4. Dichelobacter nodosus - G-, obligate anaerobe
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8
Q

What 3 virulence factors aid in Fusobacterium necrophorum attachment to host cells?

A
  1. hemagglutinins
  2. pili
  3. outer membrane proteins (FomA)
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9
Q

What 4 toxins act as virulence factors for Fusobacterium necrophorum?

A
  1. leukotoxin - lyses leukocytes (neutrophil and macrophage apoptosis)
  2. LPS - endotoxin
  3. hemolysin - lyse erythrocytes to impair oxygen transport and create an anaerobic environment
  4. dermonecrotic toxin - lyse collagen
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10
Q

What 2 media does Fusobacterium necrophorum grow best on?

A
  1. blood agar supplemented with hemin and vitamin K1
  2. Fusobacterium selective agar (FSA)
    (in an anaerobic culture)
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11
Q

What molecular analysis is used to confirm a Fusobacterium necrophorum infection?

A

PCR - IktA gene —> codes for leukotoxin

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12
Q

How are Fusobacterium necrophorum infections treated?

A
  • antibiotic therapy (penicillin G, sulfonamides, metronidazole, ampicillin, florfenicol, ceftiofur)
  • surgical intervention to debride infected tissue
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13
Q

What is calf diphtheria? What are the most affected hosts?

A

ulcerative necrosis of the cheek, tongue, pharynx, and larynx caused by Fusbacterium necrophorum
- AKA: oral necrobacillosis, necrotic pharyngitis or laryngitis

calves under 3 months

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14
Q

What are the 2 forms of calf diphtheria?

A
  1. oral form (necrotic stomatitis) - ulceration of the oral mucosa and swelling of the cheek
  2. laryngeal form (necrotic laryngitis) - ulceration of the larynx
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15
Q

What are 3 symptoms of the oral form of calf diphtheria?

A
  1. cheek swelling
  2. salivation
  3. tongue ulceration
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16
Q

What are the clinical features of the laryngeal form of calf diphtheria? What 2 things are commonly seen on postmortem examination?

A

stridor (“roaring”) and difficulty feeding (laryngeal obstruction)

  1. caseous necrosis
  2. soft tissue swelling
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17
Q

What are the 5 steps of the pathogenesis of calf diphtheria?

A
  1. eating abrasive feeds/tube feeding
  2. abrasions/trauma
  3. invasion of Fusobacterium necrophorum
  4. inflammation
  5. necrosis, ulceration, and abscesses in oral cavity, pharynx, and larynx
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18
Q

What is expected on a bacterial culture from specimen expected to be infected with Fusobcterium necrophorum?

A

polymicrobial —> F. necrophorum + Trueperella pyogenes from laryngeal swabs from animals with clinical laryngitis

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19
Q

What are 2 options for calf diphtheria treatment?

A
  1. systemic administration of sulfonamides or tetracyclines
  2. NSAIDs

(early treatment is more effective)

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20
Q

What is the most likely causative agent of liver abscesses in feedlot cattle (and rarely feedlot lambs)?

A

Fusobacterium necrophorum + Trueperella pyogenes

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21
Q

How does Fusobacterium necrophorum cause liver abscesses?

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A
  • 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
22
Q

Clinical signs of Fusobacterium necrophorum liver abscesses are rare. What are 2 possible signs?

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A
  1. reduced feed intake
  2. weight loss

(subclinical —> usually detected at the time of slaughter)

23
Q

What are 3 major ways of preventing Fusobacterium necrophorum liver abscesses? How can it be treated?

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A
  1. vaccine against leukotoxin
  2. antibiotics
  3. nutritional management - decrease carbohydrates to avoid ruminal acidosis

procaine penicillin G, oxytetracycline, ampicillin trihydrate

24
Q

What is bovine footrot? What are 3 common causative agents?

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A

infectious disease characterized by inflammation of the foot and subsequent lameness

  1. Fusobacterium necrophorum
  2. Porphyromonas levii
  3. Trueperella pyogenes
25
What are 6 symptoms of bovine footrot?
1. lameness 2. swelling of the interdigital space 3. necrotic lesions with a foul odor in the interdigital space 4. loss of appetite 5. fever, pain 6. chronic arthritis if untreated
26
What are 3 ways to treat bovine footrot?
1. systemic antibiotics 2. removal of necrotic tissue with a topical antibiotic 3. footbaths containing zinc sulphate
27
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
28
What is thrush?
chronic disease in horses by Fusobacterium necrophorum infection in the frog ---> hoofrot
29
What are the 4 clinical signs of thrush (hoofrot)? How is it treated?
1. foul smelling discharge in the frog (often black) 2. loss of frog shape 3. tenderness of the frog 4. lameness debridement, footbaths, antibiotics - prevented with environmental hygiene and hoof care
30
What is metritis? What are 4 clinical symptoms?
acute inflammation of the uterus within 21 days postpartum, commonly caused by Fusobacterium necrophorum 1. enlarged uterus 2. fetid, watery, red-brownish uterine discharge 3. fever 4. reduced milk production and appetite
31
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)
32
Metritis is commonly a polymicrobial infection. What are the 4 most common etiological agents?
1. Fusobacterium necrophorum 2. Bacteroides pyogenes 3. Porphyromonas levii 4. Helcococcus ovis
33
What are the 3 outcomes of metritis in cows? How is it commonly treated?
1. reduced milk production 2. reduced reproduction 3. increased culling - significant economic loss antibiotic treatment: ceftiofu***r, ampicillin, oxytetracycline
34
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
35
What are the 4 clinical signs of necrotic rhinitis? How is it treated?
1. necrosis of the snout 2. foul-smelling nasal discharge 3. face swelling 4. sneezing sulfonamides
36
Necrotic vs. atrophic rhinitis:
37
What is Dichelobacter nodosus?
Gram-negative, non-motile, obligate anaerobic rods in the phylum Proteobacteria
38
What is Dichelobacter nodosus a major cause of?
footrot in sheep and goats (+ Fusobacterium necrophorum)
39
What 2 virulence factors does Dichelobacter nodosus have?
1. type IV fimbriae (fimA) 2. production of serine proteases
40
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)
41
Fusobacterium and Dichelobacter summary:
42
Bacteroides, Porphyromonas, and Prevotella are.... a. spore-forming, Gram-positive anaerobes b. non-spore-forming, Gram-negative anaerobes
B (A = Clostridium)
43
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)
44
Which of the following is the most likely to be associated with periodontal disease in dogs? a. Prevotella b. Porphyromonas
B
45
Which of the following virulence factors is involved in abscess formation of anaerobic bacteria? a. capsule b. LPS
A - antiphagocytic (B = endotoxin, septic shock)
46
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)
47
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
48
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)
49
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)
50
What is chicken foot disease called? What microorganisms are likely responsible for these foot infections?
- Bumblefoot (pododermatitis) - Staphylococcus aureus - E. coli - Pseudomonas
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