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Veterinary Bacteriology & Mycology > Actinobacillus > Flashcards

Actinobacillus Flashcards

1
Q

What kind of bacteria are Actinobacillus? How does it grow in TSI media? MacConkey?

A

small Gram-negative coccobacillus +/- filaments

weak fermentaters without gas —> orange

some can grow —> small, red colonies

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2
Q

What are 2 characteristics of Actinobacillus colonies on blood agar? Where are they typically found?

A
  1. colonies may be sticky
  2. some are β-hemolytic

obligate parasite of mucosal surfaces

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3
Q

What are the 4 major species of Actinobacillus and their hosts?

A
  1. A. lingnieresii - cattle, sheep, pigs
  2. A. pleuropneumoniae - pigs
  3. A. suis - pigs
  4. A. equuli subsp equuli - horses and pigs
    - subsp haemolyticus - horses
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4
Q

In what animals does Actinobacillus pleuropneumoniae cause disease? What are the 2 biovars?

A

absolutely specific for pigs

BIOVAR 1 - requires V (NAD) factor and chocolate agar
BIOVAR 2 - doesn’t require V (NAD) factor

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5
Q

How does Actinobacillus pleuropneumoniae grow on blood agar? What serotypes are most common in US?

A

hemolytic

1, 5, 7

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6
Q

What is Actinobacillus pleuropneumoniae the causative agent of? What are 3 symptoms? When is transmission common?

A

swine pleuropneumonia
1. fibrinous pleuritis and pneumonia
2. hemorrhagic and necrotic lesions
3. subclinical to acute infection

chronic infections and carriers commonly spread disease to nonimmune herds

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7
Q

What are the 5 major clinical signs of swine pleuropneumonia? What tends to happen in pigs that recover?

A
  1. trembling
  2. anorexia
  3. dyspnea
  4. fever
  5. hemorrhage from nose and mouth

may continue to carry bacteria and be a source of new infections

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8
Q

What are 4 virulence factors of Actinobacillus pleuropneumoniae?

A
  1. capsule (serotypes)
  2. lipopolysaccharides (endotoxin)
  3. 4 RTX exotoxins (lytic for red and/or white blood cells)
  4. adhesions
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9
Q

What is responsible for hemorrhagic and necrotic lesions in Actinobacillus pneumoniae infection?

A

RTX toxins

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10
Q

Why dose Actinobacillus pleuropneumonia tend to have high virulence? What are some compromising factors?

A

not all produce the same exotoxins

  • stress
  • previous infection
  • overcrowding
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11
Q

How can Actinobacillus pleuropneumoniae infection be controlled?

A

management - use closed herds and separate animals at different production stages

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12
Q

How is immunity to Actinobacillus pleuropneumoniae acquired? What tends to enhance opsonization and clearance?

A

provided by NEUTRALIZING antibodies to RTX (repeats in toxins) toxins

antibodies to capsule and somatic antigens —> can make infection worse by causing macrophages to phagocytize bacteria without exotoxin neutralization

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13
Q

Why don’t bacterins work well to develop immunity to Actinobacillus pleuropneumoniae? What is the best course?

A

cannot induce neutralizing antibodies to labile exotoxins

live attenuated vaccines - induce neutralizing antibodies to toxins

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14
Q

How do the 2 subspecies of Actinobacillus equuli compare?

A

EQUULI: resides primarily in tonsils and intestinal/reproductive tracts of horses and pigs, grows on MacConkey agar, nonhemolytic, contains RTX toxin

HAEMOLYTICUS: infects horses primarily in the respiratory tract, hemolytic, contains RTX toxin, less common

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15
Q

What is the causative agent of Sleepy Foal Disease? When is it typically obtained? What happens when co-infection occurs?

A

Actinobacillus equuli subsp. equuli

in utero or during birth - foal bacteremia

(Strongylus vulgaris in cranial mesenteric artery and its branches) - aneurysms

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16
Q

What are 4 common symptoms of Sleepy Foal Disease?

A
  1. bacteremia/septicemia
  2. enteritis (commonly only presentation in acute cases)
  3. abscesses and lesion present i kidneys and joints in less acute infections
  4. facial cellulitis
17
Q

How does Actinobacillus equuli subsp. equuli affect pigs?

A
  • death in sows
  • pyrexia, arthritis, and mortality in piglets
18
Q

What animals are primarily affected by Actinobacillus equuli subsp. haemolyticus? What does this cause? How is it transmitted to other species

A

adult horses - abortion, stillborn fetus, metritis, mastitis, meningitis, respiratory disease*, wound infections, bacteremia, arthritis, endocarditis, inflammed rounds

wounds following horse bites

19
Q

What are the 3 major virulence factors of Actinobacillus equuli?

A
  1. LPS endotoxin
  2. adherence factors
  3. one RTX toxin (weak)
20
Q

What are 5 compromising factors to Actinobacillus equuli nfection?

A
  1. mare carrying A. equuli in genital tract prior to delivery (screen and treat before delivery)
  2. stress (overtraining)
  3. infection
  4. climate/weather
  5. parasitism (S. vulgaris)
21
Q

What is the best way to prevent Actinobacillus equuli infection?

A
  • greater attention to sanitation in birthing environment
  • maternal antibodies in colostrum
  • prebreeding culture screening
22
Q

In what animals do Actinobacillus lignieresii cause disease? Where is it commonly found? What does it require for initial isolation?

A

predominately in cattle and sheep, but may rarely cause infection in humans

commensal of oral cavity

serum/blood + CO2

23
Q

What is Actinobacillus lignieresii the causative agent of? What does this cause?

A

“wooden tongue” or Actinobacillosis

tumor-like (granuloma) lesions of the tongue and oral cavity that may ulcerate, commonly following trauma where the bacteria is able to spread to internal organs and to skin

24
Q

What happens when Actinobacillus lignieresii infection becomes chronic?

A

form granules similar to those caused by Actinomyces bovis, but smaller

25
Q

What are granulomas?

A

compact collection of mature mononuclear phagocytes which may or may not be accompanied by accessory features such as necrosis or infiltration of other inflammatory leukocytes
(common in wooden tongue / actinobacillosis)

26
Q

What are 3 virulence factors of Actinobacillus lignieresii? What does its resistance to host defenses cause?

A
  1. LPS
  2. one RTX toxin (weak)
  3. dissemination ability

induction of chronic, granulomatous inflammation

27
Q

What is the main compromising factor of Actinobacillus lignieresii?

A

invasion of tissues following wounds or trauma
- normal part of the flora
- self-inoculation of buccal epithelium by foreign material (commonly rough feed)

28
Q

What is the most imporant immunity against Actinobacillus lignieresii?

A

cellular immuity —> Th1 response

29
Q

What is recommended for Actinobacillus lignieresii treatment? How can infection be prevented?

A

sodium/potassium iodide IV or in local lesions to effectively stop the acute signs of disease (discouraged if going to slaughter

avoid feeding on coarse feedstuffs

30
Q

Where is Actinobacillus suis commonly found? How does it grow on MacConkey agar and blood agar?

A

swine mucosal surfaces

will grow on MacConkey, typically sticky and adherent

hemolytic due to RTX toxins

31
Q

What is Actinobacillus suis the causative agent of? How does this present?

A

bacteremia in piglets 1-8 weeks old

  • endocarditis, pericarditis, edema, and petechiae throughout organs
  • febrile respiratory distress, neurological symptoms, death
32
Q

How does Actinobacillus suis infection compare in adult pigs? What causes infection? What is likely the source of infection?

A

lesions are more localized (arthritis, pneumonia, abscesses)

stress

upper respiratory tract with dissemination resulting in vascular hemorrhage and necrosis

33
Q

What are the 4 major virulence factors of Actinobacillus suis?

A
  1. one RTX toxin
  2. capsule
  3. LPS
  4. adhesions
34
Q

What does the RTX toxin in Actinobacillus suis typically cross-react with?

A

RTX toxins of A. pleuropneumoniae

35
Q

How is Actinobacillus suis transmitted?

A

bacteria are carrier in the respiratory tract and tonsils of healthy and infected pigs and passes through the respiratory system to other young pigs

36
Q

How do piglets acquire immunity from Actinobacillus suis? What is the best form of immunity?

A

passive immunity from colostrum

antibodies against RTX toxins

37
Q

How must all Actinobacillus be isolated?

A

in pure culture or predominance because they are part of the normal flora

38
Q

How does the growth of Actinobacillus pleuropneumoniae, lignieresii, and equuli/suis compare?

A

A. pleuropneumoniae —> most require V (NAD) factor, chocolate agar, or blood/staph streak for growth

A. lignieresii —> requires blood and CO2 for growth with granules comonly present

A. equuli/suis —> can be isolated on MacConkey agar

Veterinary Bacteriology & Mycology (47 decks)

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