Difference between revisions of "Actinobacillus species"

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<big><center>[[Infectious agents and parasites|'''BACK TO INFECTIOUS AGENTS AND PARASITES''']]</center></big>
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#REDIRECT[[:Category:Actinobacillus species]]
<big><center>[[Bacteria|'''BACK TO BACTERIA''']]</center></big>
 
 
 
* Cause [[Peritoneal cavity - inflammatory#In horses|peritonitis in horses]]
 
 
 
===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 [[General Pathology - Chronic Inflammation#Granulomatous Inflammation|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
 
**[[Muscles - inflammatory#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
 
**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)
 
*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 [[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
 
*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 spp.|''Staphylococcus aureus'']]
 
**The bacteria on the palatine tonsil may remain 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 [[Joints - inflammatory#In Horses|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
 

Latest revision as of 11:12, 10 May 2010