Haemophilus Flashcards
What 3 genera make up the family Pasteurellaceae?
- Haemophilus (Histophilus, Glasserella, Avibacterium)
- Actinobacillus
- Pasteurella (Mannheimia)
When is Pasteurellaceae infection most common?
opportunistic pathogen of farm animals —> prior infection, stress
What is the structure of Haemophilus? How does it grow in TSI media?
Gram-negative coccobacullus
weakly fermentative —> orange, weak acid
What 2 factors are required for Haemophilus growth? What kind of parasite is it considered?
(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
What are the main 3 Haemophilus species and their hosts?
- Avibacterium paragallinarum - chicken
- Glasserella parasuis - pigs
- Histophilus somni - cows
What does Glasserella parasuis require for growth? What affects serotyping?
V (NAD) factor only
capsule and lipooligosaccharide (LOS)
What is Glasserella parasuis the causative agent of? In what animals is it most common? When are they most susceptible?
Glasser’s Disease - polyserositis
young pigs (nursery mortalitiy)
- pigs already infected with PRRS or are from SPF herds
What are 2 characteristics of Glasser’s Disease?
- polyserositis, fibrinous inflammation of serous membranes (pericardium, liver)
- purple ears due to bacteremia
How can Glasser’s Disease affect older pigs? When is it most common for older pigs to become infected? What are 3 differentials?
- respiratory disease
- chronic pleurisy
following previous infection of mycoplasma or virus
P. multocida, Bordetella, Actinobacillus
What are the 4 main virulence factors of Glasserella parasuis? What does it lack?
- capsule
- lipooligosaccharide (endotoxin)
- adherence factors (serous membranes)
4 membrane proteins
exotoxins
What are adherence factors used for in Glasserella parasuis disease? What are some examples?
host colonization by attachment to mucosal epithelial cells
pili, LOS, membrane proteins
What are lipooligosaccharides? How does each part of it affect virulence of Glasserella parasuis?
polysaccharide lacking O side chains in the LPS of Haemophilus
lipid A = endotoxic —> chronic inflammation —> fibrin
more oligosaccharide —> antigenic
What are 2 compromising factors of Glasserella parasuis infection?
- viral infection associated with respiratory disease
- stress is associated, but not required as newborn pigs are already compromised
What is Glasser’s Disease predominantly the result of?
host inflammation —> trying to remove a pathogen it cannot
How is immunity to Glasserella parasuis obtained?
mediated by antibodies to the capsule (15 types of capsules!)
- humoral immunity is most important
What are 2 vaccination options for Glasserella parasuis? In what 3 ways is it treated/controlled?
- bacterins (killed organisms) effective against homologous serotype - not very long-lasting
- 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
What is Avibacterium paragallinarum specific for? What dose it require for growth? How does it grow on blood agar?
avian species
V (NAD) factor only
non-hemolytic
What is Avibacterium paragallinarum the causative agent of? What are 2 symptoms?
Fowl coryza (acute rhinitis)
- inflammation of turbinates and sinus epithelium
- air sacculitis
What is the morbidity and mortality of Fowl coryza?
(Avibacterium paragallinarum)
high morbidity, low mortality
Fowl coryza, airsacculitis:
(Avibacterium paragallinarum)
Fowl coryza, nares and URT inflammation:
What are the 4 major virulence factors of Avibacterium paragallinarum? What is not recognized?
- capsule
- lipooligosaccharide
- adherence factors
- membrane proteins
exotoxins
What are 2 compromizing factors of Avibacterium paragallinarum infection? What is disease the result of?
- viral or mycoplasma infection
- stress
host inflammation
How is immunity to Avibacterium paragallinarum acquired?
mediated by antibodies to capsule
- humoral immunity most important
What is the best type of vaccination for Avibacterium paragallinarum?
bacterins against serotypes A, B, and C —> only can work for one serotype
- produced antibodies against capsule
What species make up Histophilus somni? What are they specific for?
Haemophilus somnus, Haemophilus agni, Histophilus ovis
bovines and sheep
What does Histophilus somni require for growth? How do colonies grow on agar?
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
Where is Histophilus somni typically found? How does it cause infection?
ruminant genital and respiratory tract
dissemination via bloodstream and localizes into the brain, heart, and joints, typically due to inflammation of the endothelium
What is hallmark of Histophilus somni infection? What is required to cause infection?
vasculitis due to inflammation of endothelium
stress AND viral infection —> feedlot disease, not common in cows in open pastures
What are the 2 most common diseases that Histoophilus somni cause? 4 others?
- pneumonia (BRDC, shipping fever)
- myocarditis (bioflim)
- thrombotic meningoencephalitis
- reproductive failure
- arthritis
- bacteremia
What are some common signs of thrombtic meningoencephalitis caused by Histophilus somni?
- eye drooping
- nasal discharge
- depression
- uveitis
What causes myocarditis in Histophilus somni infection?
bacteria aggregate into biofilm structures and adhere to venous endothelium with fibrin and neutrophil invasion
When does Histophilus somni typically form biofilms? What is the purpose?
under most growth conditions and in host tissue
more resistant to antibiotics and host defenses, but induces less inflammation
What is produced by Histophilus somni when in bioflin aggregates?
exopolysaccharide
What is the major virulence factor of Histophilus somni? What does it do?
lipooligosaccharide endotoxin
causes apoptosis of endothelial cells, leading to vasculitis
How does the phase of lipooligosaccharides in Histophilus somni alter in vivo?
antigenic epitopes change and enable the bacteria to evade host immunity by taking up sialic acid (which is commonly found in the host)
What additional receptor is present on Histophilus somni? What does it do?
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
How does Histophilus somni survive within phagocytic cells?
inhibits phagosome-lysosome fusion
What is the toxic motif present in IgG binding protein A of Histophilus somni target?
bovine endothelial cells and macrophages —> vasculitis
What are the 2 major compromising factors of Histophilus somni? What causes disease?
- stress
- previous infection
host inflammation
What is Histophilus somni virulence largely due to? What factors most into passive immunity?
avoiding host immune response within phagocytic cells
antibodies to fic motif
What is the best route of vaccination available for Histophilus somni? How is it limited?
bacterins - best for TME
phase variation and IgG binding proteins on bacteria
What mediates host specificity of Histophilus somni? Why can’t the bacteria infect other animals?
adherence and iron acquisition
host-specific bacteria obtain iron from host transferrin and can only use that specific transferrin
What is unique about the process of isolating Haemophilus species?
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)
What type of serological test is used for Heamophilus species identification?
complement fixation test
- slide or tube agglutination isn’t very sensitive
- ELISA for outer membrane protein or exopolysaccharide
How are Haemophilus infections typically treated?
antibiotics
- use least expensive
- AMR can occur, susceptibility test needed
