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===''Actinobacillus pleuropneumoniae''===
 
===''Actinobacillus pleuropneumoniae''===
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*Contagious porcine pleuropneumonia
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*Contagious porcine pleuropneumonia especially of pigs under 6 months
 
*Endemic in UK
 
*Endemic in UK
 
*Most strains are NAD-dependent (grow on Heated Blood agar)
 
*Most strains are NAD-dependent (grow on Heated Blood agar)
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*12 serotypes causing the same disease
 
*12 serotypes causing the same disease
 
*Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
 
*Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
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*Pathogenesis and pathogenicity:
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**Virulent strains possess capsules which are antiphagocytic and immunogenic
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**Fimbriae allow the bacteria to attach to cells of the respiratory tract
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**Produce three cytotoxins which belong to the repeats-in-structural-toxin (RTX)  cytolysin family
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**RTX toxins:
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***Several peptide repeats within the molecules
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***Produced by various Gram-negative bacteria
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***Possess four contiguous genes, A, B, C and D
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***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
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***ApxI is a strong haemolysin with cytolytic activity
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***ApxII is a weak haemolysin
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***ApxIII is a cytotoxin
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***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
 
*Acute disease in susceptible herds with high morbidity and mortality
 
*Causes [[Bacterial infections#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
 
*Causes [[Bacterial infections#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
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*The bacteria on the palatine tonsil are undetected by serologucal tests and swabbing, and can therefore cause an outbreak in naive pigs
 
*The bacteria on the palatine tonsil are undetected by serologucal tests and swabbing, and can therefore cause an outbreak in naive pigs
 
*Killed and bacterin vaccines are available   
 
*Killed and bacterin vaccines are available   
*Produce one or two RTX group cytolytic toxins
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*RTX toxins:
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**'Repeat in ToXin' - named because there are several peptide repeats within the molecules
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**Produced by various Gram-negative bacteria
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**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
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**Different ''Actinobacillus pleuropneumonia'' serotypes secrete a particular combination of toxins; American serotypes secrete ApxI and II; European serotypes secrete ApxII and III
       
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