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17 Cards in this Set

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  • Back
What kind of bacteria is Bacteroides fragilis? (gram? spore?)
Bacteroides species are anaerobic, bile-resistant, non-spore-forming, gram-negative rods.

neonatal diarrhea in foals, calves, piglets, lambs. bovine abortion feline, canine abscesses.
Is bacteroides fragilis a commensal? Is it opportunistic? Is it pathogenic?
- Typically part of the beneficial commensal flora. Helps maintaining intestinal immunity.
- But can also cause disease when there is commensal flora imbalance.
- Main pathogenic species of the genus Bacteroides due to its potent virulence factors.
- Constitutes ~ 2% of normal colonic population in humans.
What disease is Bacteroides fragilis associated with? How is it well suited for these pathogenicities?
- Associated with intra-abdominal abscesses, soft tissue infections and bacteremias.
- The variable surface antigens allows high adaptability to GI microenvironments.
- Its ability to tolerate and use oxygen, allows better growth in mucosal surfaces, where partial tension of oxygen is higher than in the lumen.
What are the virulence factors of bacteroides fragilis?
- Adherence to tissues (Fimbriae and agglutinins; capsule is the most important, pili in those without capsule).
- Protection from the host immune response (Polysaccharide capsule, LPS and variety of enzymes responsible for tissue destruction).
- Destruction of tissues (Capsule is responsible for abscess formation, and histolytic enzymes for tissue destruction, BFT).
What does the capsule of Bacteroides fragilis induce?
- Capsule: formed by polysaccharides A & B induces intra-abdominal abscesses
- Most important virulence factor
associated with adhesion to
epithelial surfaces.
- Polysaccharide A and B (PA & PB).
- PA & PB possess zwitterionic motifs necessary for activity of these molecules.
What is the function of BFT? (hint, it's an enterotoxin)
Bacteroides fragilis enterotoxin (BFT) or fragelysin:

-  Destroys zonula adherence tight junctions in the intestinal epithelium by cleaving E-cadherin.
-  Leak of epithelial barrier resulting in diarrhea.
-  BFT also induces fluid secretion of intestinal epithelial cells.
Match saccharolytic and asaccharolytic with Prevotella and Porphyromonas.
Prevotella genus (saccharolytic)
Porphyromonas genus (asaccharolytic)
What kind of bacteria are Prevotella and Porphyromonas (gram)?

What kind of disease do they cause?
Gram neg anaerobes

- Species of Prevotella and Porphyromonas are mainly associated with oral and bite-wound infections.
- Periodontal disease is the most common oral disease of adult animals including: gingivitis, periodontitis and periodontal abscesses.

-Porphyromonas gulae strains cause animal gingival sulcus.
-Prevotella melaninogenica isolated from footrot, works in synergy with Fusobacterium necrophorum to produce infection.
What are the virulence factors of Prevotella and Porphyromonas?
- Anaerobic protection (catalase, superoxide dismutase,
hemolysin and LPS)
- Immune protection (capsule, complement degradation,
proteases that degrade IgA & IgG)
- Attachment (capsule, pili, hemagglutanin)
- Invasion (collagenase, protease, RNase, DNase, and phospholipase)
What kind of bacterium is fusobacterium necrophorum? (gram?)

What kind of pathogenicity does it cause?
Gram neg anaerobe

Causative agent of variety of necrotic infections in animals with severe economical impact:
- Necrotic bacillosis (liver abscesses)
- Necrotic laryngitis (Calf diphteria)
- Involved in early invasion of the hood and development of footrot
What are the reservoirs of Fusobacterium necrophorum?
Mouth, GI and urogenital tracts and also soil.
What are the two main virulence factors of fusobacterium necrophorum?
Has many, but the main ones are:

Leukotoxin: Protects against neutrophil phagocytosis also cytotoxic to neutrophils, macrophages, hepatocytes, and rumen epithelial cells.

Endotoxin: Creates anaerobic environment. (Lipopolysaccharide cell-wall component.) Has necrotic effect and induces disseminated
intravascular coagulation.
What is the success of inducing immunity against fusobacterium necrophorum?
- Serum antibodies against F. necrophorum are present in both, healthy and infected animals, therefore, the importance of immunity in F. necrophorum disease is unclear.
- Leukotoxin is highly immunogenic and elicits a high leukotoxin antibody titer when leukotoxin toxoid is injected into animals, provides significant protection. So has potential to be a part of the successful vaccine.
What kind of bacterium is dichelobacter nodosus? What does this bug cause of importance in vet med?

What is the main reservoir of this bacteria?
Gram neg. anaerobe

Major infectious agent of ovine footrot, affecting sheep and goats.

Causes significant economic losses
Environmental reservoir:
- Infected sheep and goat are main reservoir
- Transport trucks contaminated with infected soil and feces
- D. nodosus does not survive more than two weeks on pasture.
What is the main virulence factor of Dichelobacter nodosus?
Type IV pili: forms a series of pilis on the surfaces. Twitching of type IV pili of D. nodosus gives it motility. The pili give the bacterium ability to colonize.

Knocking out the function of type IV pili abolishes the motility and adherence of the bacterium.

As if all that wasn't enough, type IV pili also is involved in protease secretion that is involved in separating the skin from the horn. It is thought that the pili pushes out the protease as a piston.
How many recognized serotypes of type IV pili of Dichelobacter nodosus are there?
9 recognized serogroups (A-I) have been identified.
Are you able to vaccinate against Dichelobacter nodosus?
- Weak immune response of sheeps upon challenge
- Immunization is serogroup specific
- Coarse-wooled British breeds are more resistant than Merino sheep.