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Veterinary Bacteriology & Mycology > Haemophilus > Flashcards

Haemophilus Flashcards

1
Q

What 3 genera make up the family Pasteurellaceae?

A
  1. Haemophilus (Histophilus, Glasserella, Avibacterium)
  2. Actinobacillus
  3. Pasteurella (Mannheimia)
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2
Q

When is Pasteurellaceae infection most common?

A

opportunistic pathogen of farm animals —> prior infection, stress

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3
Q

What is the structure of Haemophilus? How does it grow in TSI media?

A

Gram-negative coccobacullus

weakly fermentative —> orange, weak acid

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4
Q

What 2 factors are required for Haemophilus growth? What kind of parasite is it considered?

A

(blood factors)
1. X factor - hemin
2. V factor - NAD coenzyme in ETC for respiration

obligate parasite of host mucosal surfaces —> urogenital tract and upper respiratory tract only

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5
Q

What are the main 3 Haemophilus species and their hosts?

A
  1. Avibacterium paragallinarum - chicken
  2. Glasserella parasuis - pigs
  3. Histophilus somni - cows
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6
Q

What does Glasserella parasuis require for growth? What affects serotyping?

A

V (NAD) factor only

capsule and lipooligosaccharide (LOS)

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7
Q

What is Glasserella parasuis the causative agent of? In what animals is it most common? When are they most susceptible?

A

Glasser’s Disease - polyserositis

young pigs (nursery mortalitiy)
- pigs already infected with PRRS or are from SPF herds

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8
Q

What are 2 characteristics of Glasser’s Disease?

A
  1. polyserositis, fibrinous inflammation of serous membranes (pericardium, liver)
  2. purple ears due to bacteremia
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9
Q

How can Glasser’s Disease affect older pigs? When is it most common for older pigs to become infected? What are 3 differentials?

A
  • respiratory disease
  • chronic pleurisy

following previous infection of mycoplasma or virus

P. multocida, Bordetella, Actinobacillus

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10
Q

What are the 4 main virulence factors of Glasserella parasuis? What does it lack?

A
  1. capsule
  2. lipooligosaccharide (endotoxin)
  3. adherence factors (serous membranes)
    4 membrane proteins

exotoxins

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11
Q

What are adherence factors used for in Glasserella parasuis disease? What are some examples?

A

host colonization by attachment to mucosal epithelial cells

pili, LOS, membrane proteins

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12
Q

What are lipooligosaccharides? How does each part of it affect virulence of Glasserella parasuis?

A

polysaccharide lacking O side chains in the LPS of Haemophilus

lipid A = endotoxic —> chronic inflammation —> fibrin
more oligosaccharide —> antigenic

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13
Q

What are 2 compromising factors of Glasserella parasuis infection?

A
  1. viral infection associated with respiratory disease
  2. stress is associated, but not required as newborn pigs are already compromised
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14
Q

What is Glasser’s Disease predominantly the result of?

A

host inflammation —> trying to remove a pathogen it cannot

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15
Q

How is immunity to Glasserella parasuis obtained?

A

mediated by antibodies to the capsule (15 types of capsules!)
- humoral immunity is most important

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16
Q

What are 2 vaccination options for Glasserella parasuis? In what 3 ways is it treated/controlled?

A
  1. bacterins (killed organisms) effective against homologous serotype - not very long-lasting
  2. attenuated live
  • antimicrobials (dosen’t tend to be AMR)
  • intentional exposure at 3-5 days of age with low-dose of less virulent serotypes (RISKY)
  • protection through maternal antibodies
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17
Q

What is Avibacterium paragallinarum specific for? What dose it require for growth? How does it grow on blood agar?

A

avian species

V (NAD) factor only

non-hemolytic

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18
Q

What is Avibacterium paragallinarum the causative agent of? What are 2 symptoms?

A

Fowl coryza (acute rhinitis)

  1. inflammation of turbinates and sinus epithelium
  2. air sacculitis
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19
Q

What is the morbidity and mortality of Fowl coryza?

A

(Avibacterium paragallinarum)
high morbidity, low mortality

20
Q

Fowl coryza, airsacculitis:

A

(Avibacterium paragallinarum)

21
Q

Fowl coryza, nares and URT inflammation:

A
22
Q

What are the 4 major virulence factors of Avibacterium paragallinarum? What is not recognized?

A
  1. capsule
  2. lipooligosaccharide
  3. adherence factors
  4. membrane proteins

exotoxins

23
Q

What are 2 compromizing factors of Avibacterium paragallinarum infection? What is disease the result of?

A
  1. viral or mycoplasma infection
  2. stress

host inflammation

24
Q

How is immunity to Avibacterium paragallinarum acquired?

A

mediated by antibodies to capsule
- humoral immunity most important

25
Q

What is the best type of vaccination for Avibacterium paragallinarum?

A

bacterins against serotypes A, B, and C —> only can work for one serotype
- produced antibodies against capsule

26
Q

What species make up Histophilus somni? What are they specific for?

A

Haemophilus somnus, Haemophilus agni, Histophilus ovis

bovines and sheep

27
Q

What does Histophilus somni require for growth? How do colonies grow on agar?

A

neither X or V factors —> requires blood and CO2

colonies are yellow when picked up with a white swab and are weakly hemolytic or nonhemolytic

28
Q

Where is Histophilus somni typically found? How does it cause infection?

A

ruminant genital and respiratory tract

dissemination via bloodstream and localizes into the brain, heart, and joints, typically due to inflammation of the endothelium

29
Q

What is hallmark of Histophilus somni infection? What is required to cause infection?

A

vasculitis due to inflammation of endothelium

stress AND viral infection —> feedlot disease, not common in cows in open pastures

30
Q

What are the 2 most common diseases that Histoophilus somni cause? 4 others?

A
  1. pneumonia (BRDC, shipping fever)
  2. myocarditis (bioflim)
  3. thrombotic meningoencephalitis
  4. reproductive failure
  5. arthritis
  6. bacteremia
31
Q

What are some common signs of thrombtic meningoencephalitis caused by Histophilus somni?

A
  • eye drooping
  • nasal discharge
  • depression
  • uveitis
32
Q

What causes myocarditis in Histophilus somni infection?

A

bacteria aggregate into biofilm structures and adhere to venous endothelium with fibrin and neutrophil invasion

33
Q

When does Histophilus somni typically form biofilms? What is the purpose?

A

under most growth conditions and in host tissue

more resistant to antibiotics and host defenses, but induces less inflammation

34
Q

What is produced by Histophilus somni when in bioflin aggregates?

A

exopolysaccharide

35
Q

What is the major virulence factor of Histophilus somni? What does it do?

A

lipooligosaccharide endotoxin

causes apoptosis of endothelial cells, leading to vasculitis

36
Q

How does the phase of lipooligosaccharides in Histophilus somni alter in vivo?

A

antigenic epitopes change and enable the bacteria to evade host immunity by taking up sialic acid (which is commonly found in the host)

37
Q

What additional receptor is present on Histophilus somni? What does it do?

A

IgG Fc receptors (IbpA) - allows bacterium to bind the Fc region of IgG, which protects it from host defenses and contains a toxic motif toxic to eukaryotic cells

38
Q

How does Histophilus somni survive within phagocytic cells?

A

inhibits phagosome-lysosome fusion

39
Q

What is the toxic motif present in IgG binding protein A of Histophilus somni target?

A

bovine endothelial cells and macrophages —> vasculitis

40
Q

What are the 2 major compromising factors of Histophilus somni? What causes disease?

A
  1. stress
  2. previous infection

host inflammation

41
Q

What is Histophilus somni virulence largely due to? What factors most into passive immunity?

A

avoiding host immune response within phagocytic cells

antibodies to fic motif

42
Q

What is the best route of vaccination available for Histophilus somni? How is it limited?

A

bacterins - best for TME

phase variation and IgG binding proteins on bacteria

43
Q

What mediates host specificity of Histophilus somni? Why can’t the bacteria infect other animals?

A

adherence and iron acquisition

host-specific bacteria obtain iron from host transferrin and can only use that specific transferrin

44
Q

What is unique about the process of isolating Haemophilus species?

A

many are part of the normal flora, so isolates need to be from sterile sites or in a pure culture on chocolate agar
- include NAD and blood/CO2 (H. somni)

45
Q

What type of serological test is used for Heamophilus species identification?

A

complement fixation test
- slide or tube agglutination isn’t very sensitive
- ELISA for outer membrane protein or exopolysaccharide

46
Q

How are Haemophilus infections typically treated?

A

antibiotics
- use least expensive
- AMR can occur, susceptibility test needed

Veterinary Bacteriology & Mycology (47 decks)

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