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Actinobacillus species (view source)

Revision as of 15:18, 20 December 2007

236 bytes added , 15:18, 20 December 2007

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===''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

*Most strains are NAD-dependent (grow on Heated Blood agar)

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*12 serotypes causing the same disease

*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

*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

*Killed and bacterin vaccines are available

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*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

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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

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