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Veterinary Bacteriology & Mycology > Fusobacterium & Dichelobacter > Flashcards

Fusobacterium & Dichelobacter Flashcards

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?

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?

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?

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?

A

infectious disease characterized by inflammation of the foot and subsequent lameness

  1. Fusobacterium necrophorum
  2. Porphyromonas levii
  3. Trueperella pyogenes
25
Q

What are 6 symptoms of bovine footrot?

A
  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
Q

What are 3 ways to treat bovine footrot?

A
  1. systemic antibiotics
  2. removal of necrotic tissue with a topical antibiotic
  3. footbaths containing zinc sulphate
27
Q

What are common ways that bovine footrot is prevented?

A
  • 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
Q

What is thrush?

A

chronic disease in horses by Fusobacterium necrophorum infection in the frog —> hoofrot

29
Q

What are the 4 clinical signs of thrush (hoofrot)? How is it treated?

A
  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
Q

What is metritis? What are 4 clinical symptoms?

A

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
Q

How are uterine discharges scored for metritis diagnosis?

A

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
Q

Metritis is commonly a polymicrobial infection. What are the 4 most common etiological agents?

A
  1. Fusobacterium necrophorum
  2. Bacteroides pyogenes
  3. Porphyromonas levii
  4. Helcococcus ovis
33
Q

What are the 3 outcomes of metritis in cows? How is it commonly treated?

A
  1. reduced milk production
  2. reduced reproduction
  3. increased culling
    - significant economic loss

antibiotic treatment: ceftiofu***r, ampicillin, oxytetracycline

34
Q

What is necrotic rhinitis? What are the most common causative agent and host?

A

chronic inflammation of the mucous membrane of the nose

Fusobacterium necrophorum
young pigs

35
Q

What are the 4 clinical signs of necrotic rhinitis? How is it treated?

A
  1. necrosis of the snout
  2. foul-smelling nasal discharge
  3. face swelling
  4. sneezing

sulfonamides

36
Q

Necrotic vs. atrophic rhinitis:

A
37
Q

What is Dichelobacter nodosus?

A

Gram-negative, non-motile, obligate anaerobic rods in the phylum Proteobacteria

38
Q

What is Dichelobacter nodosus a major cause of?

A

footrot in sheep and goats (+ Fusobacterium necrophorum)

39
Q

What 2 virulence factors does Dichelobacter nodosus have?

A
  1. type IV fimbriae (fimA)
  2. production of serine proteases
40
Q

Where should samples for Dichelobacter nodosus isolation be taken from? What media does it grow best on?

A

swabs from interdigital skin/lesions and tissue

anaerobic culture in fastidious anaerobe agar containing 10% horse blood > 4 days
(PCR + sequencing)

41
Q

Fusobacterium and Dichelobacter summary:

A
42
Q

Bacteroides, Porphyromonas, and Prevotella are….

a. spore-forming, Gram-positive anaerobes
b. non-spore-forming, Gram-negative anaerobes

A

B
(A = Clostridium)

43
Q

Which route is most likely associated with bacteremia caused by anaerobic bacteria?

a. bite wounds
b. ingestion of contaminated water

A

A - normal flora of the oral cavity of animals

(ingestion —> diarrhea + E. coli)

44
Q

Which of the following is the most likely to be associated with periodontal disease in dogs?

a. Prevotella
b. Porphyromonas

A

B

45
Q

Which of the following virulence factors is involved in abscess formation of anaerobic bacteria?

a. capsule
b. LPS

A

A - antiphagocytic

(B = endotoxin, septic shock)

46
Q

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?

A

3 = filamentous G- rods (phagocytized by neitrophils)

47
Q

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

A - obligate anaerobe

48
Q

What are the diseases associated with Fusobacterium necrophorum in cattle?

A

(necrobacillosis)
- calf diphtheria (<3 months)
- liver abscesses (feedlot cattle with high carb diets)
- metritis (postpartum dairy cows)
- footrot (lameness in beef cattle)

49
Q

A sheep showed lameness and necrotic lesions with a foul odor in the interdigital space. What microorganism is most likely responsible for these symptoms?

A

Dichelobacter nodosus
(+ Fusobacterium necrophorum as a secondary invader)

50
Q

What is chicken foot disease called? What microorganisms are likely responsible for these foot infections?

A
  • Bumblefoot (pododermatitis)
  • Staphylococcus aureus
  • E. coli
  • Pseudomonas

Veterinary Bacteriology & Mycology (47 decks)

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