Difference between revisions of "Category:Actinobacillus species"

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(Created page with '===Overview=== *Mainly pathogens of farm animals *Commensals of mucosa of upper respiratory tract and oral cavity *Cannot survive long in the environment, therefore carrier anim…')
 
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===''Actinobacillus lignieresii''===
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''[[Actinobacillus lignieresii]]''
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*Pathogenesis and pathogenicity:
 
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**Commensal in the mouth and intestinal tract of cattle and sheep
 
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**Penetrates damaged mucosa to cause chronic granulomatous inflammation of soft tissues, a condition known as Actinobacillosis
 
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**Enodogenous, sporadic infection
 
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**Lesions in the tongue, cheek, lips and sometimes in the lower gut and lungs from aspiration
 
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**Often spreads from the site of infection to lymphatics, and may cause pyogranulomatous lymphadenitis
 
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**[[Muscles Inflammatory - Pathology#Wooden tongue|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
 
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**In sheep abscesses with thick walls are produced
 
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**Feeding is impaired, causing loss of condition
 
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**Infection in the oesophageal groove can cause tympany and enlargement of the retropharyngeal lymph node, causing difficulty in swallowing and breathing
 
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**[[Bacterial skin infections - Pathology#Bacterial granulomatous dermatitis|Cutaneous lesions]] in cattle and sheep
 
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**Contamination of the environment via ulcerating lesions
 
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*Diagnosis:
 
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**Induration of tongue
 
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**Tissue sections may demonstrate pyogranulomatous foci containing club colonies
 
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**Gram negative rods may be present in smears from exudates
 
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**Cultures on blood agar and MacConkey agar, incubated for 24-72 hours
 
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**Blood agar: small, sticky, non-haemolytic clonies
 
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**MacConkey agar: slow lactose fermentation
 
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*Treatment:
 
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**Sodium iodide parenterally, or potassium iodide orally
 
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**Potentiated sulphonamides or a penicillin/streptomycin combination
 
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**Rough feed should be avoided
 
  
 
===''Actinobacillus pleuropneumoniae''===
 
===''Actinobacillus pleuropneumoniae''===

Revision as of 11:14, 10 May 2010

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


Actinobacillus pleuropneumoniae

  • Contagious porcine pleuropneumonia especially of pigs under 6 months
  • Endemic in UK
  • 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 and epidemiology:
    • Acute disease in susceptible herds with high morbidity and mortality (up to 50%)
    • 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
  • Diagnosis:
    • Haemorrhagic consolidation close to the main bronchi and fibrinous pleuritis may be suggestive
    • Specimens are cultured on chocolate agar and blood agar in 5-10% carbon dioxide for 2-3 days
    • Small colonies surrounded by clear haemolysis
    • No growth on MacConkey agar
    • Positive CAMP reaction with Staphylococcus aureus
    • Most strains are NAD-dependent (grow on Heated Blood agar)
    • Immunofluorescent- or PCR-based techniques
    • The bacteria on the palatine tonsil may remain undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
  • Treatment:
    • Antibiotics depending on the strain of bacteria
    • Prophylactic antibiotics for in-contact pigs
  • Control:
    • Killed and polyvalent bacterin vaccines as well as a subunit vaccine are available
    • Improve ventilation, avoid chilling and overcrowding

Actinobacillus equuli

  • Commensal of the equine intestinal and reproductive tract
  • Pathogenesis and clinical signs:
    • Foals infected in utero or or after birth via the umbilicus
    • Infection at birth causes severe enteritis and septicaemia within 24 hours, known as sleepy foal disease
    • Foals become pyrexic and recumbent
    • Death usually occurs within 1-2 days
    • In foals that survive neonatal infection the condition progresses to cause joint infections and purulent nephritis, enteritis or pneumonia
    • A. equuli in arthritis of horses
    • Abortion, septicaemia and peritonitis in horses
  • Diagnosis:
    • Specimens cultured on blood agar and MacConkey agar and incubated aerobically for 1-3 days
    • Sticky colonies with variable haemolysis on blood agar
    • Lactose-fermenting colonies on MacConkey agar
  • Treatment and control:
    • Antimicrobials ineffective unless early in course of disease
    • Blood trasfusion and administration of colostrum
    • Good hygiene
    • Consider prophylactic antibiotics for new-born foals
    • Bacteria susceptible to streptomycin, tetracyclines and ampicillin
  • In other animals:
    • Septicaemia in piglets
    • Arthritis and enteritis in pigs
    • Enteritis in calves
    • RTX group cytotoxin present


Actinobacillus suis

  • May be present in upper respiratory tract of sows
  • Pathogenicity and clinical signs:
    • Infection of piglets via aerosol or possibly skin abrasions
    • Fatal septicaemia in piglets 1-8 weeks old
    • Mortality up to 50% in some litters
    • Fever, respiratory distress, prostration and paddling of forelimbs seen in piglets
    • Petechial and ecchymotic haemorrhages in many organs
    • Interstitial pneumonia, pleuritis, meningoencephalitis, myocarditis and arthritis
    • 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
  • Diagnosis:
    • Specimens cultured on blood agar and MacConkey agar for 1-3 days
    • Sticky haemolytic colonies
    • Pink, lactose-fermenting colonies on MacConkey agar
  • Treatment and control:
    • Bacteria usually susceptible to ampicillin, carbenicillin, potentiated sulphonamides and tetracyclines
    • Disinfect contaminated pens
  • Other animals:
    • Septicaemia and pneumonia in foals
    • Pneumonia in pigs and horses


Actinobacillus seminis

  • Epididymitis in young rams (4-8 months)
  • Polyarthritis in lambs
  • Organism found in prepuce
  • Opportunistic infection causing abscesses in epididymides
  • May be purulent discharge onto scrotal skin
  • Specimens cultured on blood agar and incubated aerobically for 1-3 days produce pin-point haemolytic colonies which are catalase-positive; no growth on MacConkey agar


Actinobacillus actinomycetemcomitans

  • Epididymitis in rams

Pages in category "Actinobacillus species"

The following 6 pages are in this category, out of 6 total.

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