Actinobacillus Flashcards
What kind of bacteria are Actinobacillus? How does it grow in TSI media? MacConkey?
small Gram-negative coccobacillus +/- filaments
weak fermentaters without gas —> orange
some can grow —> small, red colonies
What are 2 characteristics of Actinobacillus colonies on blood agar? Where are they typically found?
- colonies may be sticky
- some are β-hemolytic
obligate parasite of mucosal surfaces
What are the 4 major species of Actinobacillus and their hosts?
- A. lingnieresii - cattle, sheep, pigs
- A. pleuropneumoniae - pigs
- A. suis - pigs
- A. equuli subsp equuli - horses and pigs
- subsp haemolyticus - horses
In what animals does Actinobacillus pleuropneumoniae cause disease? What are the 2 biovars?
absolutely specific for pigs
BIOVAR 1 - requires V (NAD) factor and chocolate agar
BIOVAR 2 - doesn’t require V (NAD) factor
How does Actinobacillus pleuropneumoniae grow on blood agar? What serotypes are most common in US?
hemolytic
1, 5, 7
What is Actinobacillus pleuropneumoniae the causative agent of? What are 3 symptoms? When is transmission common?
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
What are the 5 major clinical signs of swine pleuropneumonia? What tends to happen in pigs that recover?
- trembling
- anorexia
- dyspnea
- fever
- hemorrhage from nose and mouth
may continue to carry bacteria and be a source of new infections
What are 4 virulence factors of Actinobacillus pleuropneumoniae?
- capsule (serotypes)
- lipopolysaccharides (endotoxin)
- 4 RTX exotoxins (lytic for red and/or white blood cells)
- adhesions
What is responsible for hemorrhagic and necrotic lesions in Actinobacillus pneumoniae infection?
RTX toxins
Why dose Actinobacillus pleuropneumonia tend to have high virulence? What are some compromising factors?
not all produce the same exotoxins
- stress
- previous infection
- overcrowding
How can Actinobacillus pleuropneumoniae infection be controlled?
management - use closed herds and separate animals at different production stages
How is immunity to Actinobacillus pleuropneumoniae acquired? What tends to enhance opsonization and clearance?
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
Why don’t bacterins work well to develop immunity to Actinobacillus pleuropneumoniae? What is the best course?
cannot induce neutralizing antibodies to labile exotoxins
live attenuated vaccines - induce neutralizing antibodies to toxins
How do the 2 subspecies of Actinobacillus equuli compare?
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
What is the causative agent of Sleepy Foal Disease? When is it typically obtained? What happens when co-infection occurs?
Actinobacillus equuli subsp. equuli
in utero or during birth - foal bacteremia
(Strongylus vulgaris in cranial mesenteric artery and its branches) - aneurysms
What are 4 common symptoms of Sleepy Foal Disease?
- bacteremia/septicemia
- enteritis (commonly only presentation in acute cases)
- abscesses and lesion present i kidneys and joints in less acute infections
- facial cellulitis
How does Actinobacillus equuli subsp. equuli affect pigs?
- death in sows
- pyrexia, arthritis, and mortality in piglets
What animals are primarily affected by Actinobacillus equuli subsp. haemolyticus? What does this cause? How is it transmitted to other species
adult horses - abortion, stillborn fetus, metritis, mastitis, meningitis, respiratory disease*, wound infections, bacteremia, arthritis, endocarditis, inflammed rounds
wounds following horse bites
What are the 3 major virulence factors of Actinobacillus equuli?
- LPS endotoxin
- adherence factors
- one RTX toxin (weak)
What are 5 compromising factors to Actinobacillus equuli nfection?
- mare carrying A. equuli in genital tract prior to delivery (screen and treat before delivery)
- stress (overtraining)
- infection
- climate/weather
- parasitism (S. vulgaris)
What is the best way to prevent Actinobacillus equuli infection?
- greater attention to sanitation in birthing environment
- maternal antibodies in colostrum
- prebreeding culture screening
In what animals do Actinobacillus lignieresii cause disease? Where is it commonly found? What does it require for initial isolation?
predominately in cattle and sheep, but may rarely cause infection in humans
commensal of oral cavity
serum/blood + CO2
What is Actinobacillus lignieresii the causative agent of? What does this cause?
“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
What happens when Actinobacillus lignieresii infection becomes chronic?
form granules similar to those caused by Actinomyces bovis, but smaller
What are granulomas?
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)
What are 3 virulence factors of Actinobacillus lignieresii? What does its resistance to host defenses cause?
- LPS
- one RTX toxin (weak)
- dissemination ability
induction of chronic, granulomatous inflammation
What is the main compromising factor of Actinobacillus lignieresii?
invasion of tissues following wounds or trauma
- normal part of the flora
- self-inoculation of buccal epithelium by foreign material (commonly rough feed)
What is the most imporant immunity against Actinobacillus lignieresii?
cellular immuity —> Th1 response
What is recommended for Actinobacillus lignieresii treatment? How can infection be prevented?
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
Where is Actinobacillus suis commonly found? How does it grow on MacConkey agar and blood agar?
swine mucosal surfaces
will grow on MacConkey, typically sticky and adherent
hemolytic due to RTX toxins
What is Actinobacillus suis the causative agent of? How does this present?
bacteremia in piglets 1-8 weeks old
- endocarditis, pericarditis, edema, and petechiae throughout organs
- febrile respiratory distress, neurological symptoms, death
How does Actinobacillus suis infection compare in adult pigs? What causes infection? What is likely the source of infection?
lesions are more localized (arthritis, pneumonia, abscesses)
stress
upper respiratory tract with dissemination resulting in vascular hemorrhage and necrosis
What are the 4 major virulence factors of Actinobacillus suis?
- one RTX toxin
- capsule
- LPS
- adhesions
What does the RTX toxin in Actinobacillus suis typically cross-react with?
RTX toxins of A. pleuropneumoniae
How is Actinobacillus suis transmitted?
bacteria are carrier in the respiratory tract and tonsils of healthy and infected pigs and passes through the respiratory system to other young pigs
How do piglets acquire immunity from Actinobacillus suis? What is the best form of immunity?
passive immunity from colostrum
antibodies against RTX toxins
How must all Actinobacillus be isolated?
in pure culture or predominance because they are part of the normal flora
How does the growth of Actinobacillus pleuropneumoniae, lignieresii, and equuli/suis compare?
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
