Difference between revisions of "Actinobacillus species"

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**Virulent strains possess capsules which are antiphagocytic and immunogenic
 
**Virulent strains possess capsules which are antiphagocytic and immunogenic
 
**Fimbriae allow the bacteria to attach to cells of the respiratory tract
 
**Fimbriae allow the bacteria to attach to cells of the respiratory tract
 +
**Damaged neutrophils in the lungs produce lytic enzymes
 +
**The sustained inflammatory response causes tissue necrosis
 +
**Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
 
**Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX)  cytolysin family
 
**Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX)  cytolysin family
 
**RTX toxins:
 
**RTX toxins:
Line 69: Line 72:
 
***ApxIII is a cytotoxin
 
***ApxIII is a cytotoxin
 
***Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
 
***Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
*Acute disease in susceptible herds with high morbidity and mortality
+
***Toxins introduce pores into cell membranes
*Causes [[Bacterial infections#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
+
*CLinical signs
*Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
+
**Acute disease in susceptible herds with high morbidity and mortality
*Lung scarring and pleural adhesions in many recovered animals
+
**In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
*Solid immunity develops in recovered animals to all serotypes
+
**Blood-stained froth surrounding nose and mouth
*The disease is spread between herds by carrier pigs
+
**Cyanosis
*The bacteria on the palatine tonsil are undetected by serologucal tests and swabbing, and can therefore cause an outbreak in naive pigs
+
**Pregnant sows abort
*Killed and bacterin vaccines are available   
+
**Causes [[Bacterial infections#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
 +
**Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
 +
**Lung scarring and pleural adhesions in many recovered animals
 +
**Solid immunity develops in recovered animals to all serotypes
 +
**The disease is spread between herds by carrier pigs
 +
**The bacteria on the palatine tonsil are undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
 +
**Killed and bacterin vaccines are available   
  
  

Revision as of 19:08, 20 December 2007

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Overview

  • Mainly pathogens of farm animals
  • Commensals of mucosa of upper respiratory tract and oral cavity
  • Cannot survive long in the environment, therefore carrier animals are important in their transmission
  • Cause granulomatous inflammation


Actinobacillus characteristics

  • Small Gram negative coccobacilli
  • Oxidase negative
  • Do not grow on MacConkey
  • Non-motile
  • Facultative anaerobes which ferment carbohydrates to produce acid


Actinobacillus lignieresii

  • Pathogenesis and pathogenicity:
    • Commensal in the mouth and intestinal tract of cattle and sheep
    • Penetrates damaged mucosa to cause chronic granulomatous inflammation of soft tissues, a condition known as Actinobacillosis
    • Enodogenous, sporadic infection
    • Lesions in the tongue, cheek, lips and sometimes in the lower gut and lungs from aspiration
    • Often spreads from the site of infection to lymphatics, and may cause pyogranulomatous lymphadenitis
    • Myositis and formation of fibrous tissue in the lesions lead to hardening of the tissue, hence the condition is known as 'wooden tongue' in cattle
    • In sheep abscesses with thick walls are produced
    • Feeding is impaired, causing loss of condition
    • Infection in the oesophageal groove can cause tympany and enlargement of the retropharyngeal lymph node, causing difficulty in swallowing and breathing
    • Cutaneous lesions in cattle and sheep
    • Contamination of the environment via ulcerating lesions
  • Diagnosis:
    • Induration of tongue
    • Tissue sections may demonstrate pyogranulomatous foci containing club colonies
    • Gram negative rods may be present in smears from exudates
    • Cultures on blood agar and MacConkey agar, incubated for 24-72 hours
    • Blood agar: small, sticky, non-haemolytic clonies
    • MacConkey agar: slow lactose fermentation
  • Treatment:
    • Sodium iodide parenterally, or potassium iodide orally
    • Potentiated sulphonamides or a penicillin/streptomycin combination
    • Rough feed should be avoided


Actinobacillus pleuropneumoniae

  • Contagious porcine pleuropneumonia especially of pigs under 6 months
  • Endemic in UK
  • Most strains are NAD-dependent (grow on Heated Blood agar)
  • Positive CAMP reaction
  • 12 serotypes causing the same disease
  • Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
  • Pathogenesis and pathogenicity:
    • Virulent strains possess capsules which are antiphagocytic and immunogenic
    • Fimbriae allow the bacteria to attach to cells of the respiratory tract
    • Damaged neutrophils in the lungs produce lytic enzymes
    • The sustained inflammatory response causes tissue necrosis
    • Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
    • Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX) cytolysin family
    • RTX toxins:
      • Several peptide repeats within the molecules
      • Produced by various Gram-negative bacteria
      • Possess four contiguous genes, A, B, C and D
      • A is the structural gene; B and D are required for secretion; C allows post-translational activation of the gene product of A into a functional product
      • ApxI is a strong haemolysin with cytolytic activity
      • ApxII is a weak haemolysin
      • ApxIII is a cytotoxin
      • Different Actinobacillus pleuropneumonia serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
      • Toxins introduce pores into cell membranes
  • CLinical signs
    • Acute disease in susceptible herds with high morbidity and mortality
    • In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
    • Blood-stained froth surrounding nose and mouth
    • Cyanosis
    • Pregnant sows abort
    • Causes pneumonia in pigs
    • Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
    • Lung scarring and pleural adhesions in many recovered animals
    • Solid immunity develops in recovered animals to all serotypes
    • The disease is spread between herds by carrier pigs
    • The bacteria on the palatine tonsil are undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
    • Killed and bacterin vaccines are available


Actinobacillus equuli

  • Commensal of the equine intestinal mucosa
  • Infection at birth causes severe enteritis and septicaemia within 24 hours, known as sleepy foal disease
  • In foals that survive neonatal infection the condition progresses to cause joint infections and purulent nephritis
  • A. equuli in arthritis of horses
  • Abortion in mares
  • Septicaemia in piglets
  • Arthritis and enteritis in pigs
  • Enteritis in calves
  • RTX group cytotoxin present


Actinobacillus suis

  • Fatal septicaemia in piglets 1-8 weeks old
  • Causes abscesses in joints and lungs of older pigs
  • Carried in the nasopharynx of pigs and nose of horses
  • Carriage may confer immunity to the more severe pleuropneumonia
  • Septicaemia and pneumonia in foals
  • Pneumonia in pigs and horses


Actinobacillus seminis

  • Epididymitis in rams
  • Polyarthritis in lambs


Actinobacillus actinomycetemcomitans

  • Epididymitis in rams