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| − | ===Overview=== | + | {{frontpage |
| | + | |pagetitle =Actinobacillus species |
| | + | |pagebody = Actinobacillus organisms are mainly pathogens of farm animals and commensals of the mucosa of upper respiratory tract and oral cavity. They cannot survive for long in the environment, so carrier animals are important in their transmission. Actinobacillus organisms are small Gram negative coccobacilli that are oxidase negative, non-motile facultative anaerobes that ferment carbohydrates to produce acid. They do not grow on MacConkey Agar. |
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| − | *Mainly pathogens of farm animals
| + | Clinically, they cause [[Granulomatous Inflammation|granulomatous inflammation]]. |
| − | *Commensals of mucosa of upper respiratory tract and oral cavity
| + | |contenttitle =Content |
| − | *Cannot survive long in the environment, therefore carrier animals are important in their transmission
| + | |contentbody =<big><b> |
| − | *Cause [[Chronic Inflammation - Pathology#Granulomatous Inflammation|granulomatous inflammation]]
| + | <categorytree mode=pages>Actinobacillus species</categorytree> |
| | + | </b></big> |
| | + | |logo =bugs-logo copy.png |
| | + | }} |
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| − | | + | [[Category:Bacterial Organisms]] |
| − | ===''Actinobacillus'' characteristics===
| + | [[Category:Gram negative bacteria]] |
| − | | + | [[Category:Coccobacilli]] |
| − | *Small Gram negative coccobacilli
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| − | *Oxidase negative
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| − | *Do not grow on MacConkey
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| − | *Non-motile
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| − | *Facultative anaerobes which ferment carbohydrates to produce acid
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| − | ''[[Actinobacillus lignieresii]]''
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| − | ===''Actinobacillus pleuropneumoniae''===
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| − | *Contagious porcine pleuropneumonia especially of pigs under 6 months
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| − | *Endemic in UK
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| − | *12 serotypes causing the same disease
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| − | *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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| − | **Damaged [[Neutrophils - WikiBlood|neutrophils]] in the lungs produce lytic enzymes
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| − | **The sustained inflammatory response causes tissue necrosis
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| − | **Lungs consolidated and necrotic with fibrinous pleuisy at post mortem
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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
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| − | ***Toxins introduce pores into cell membranes
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| − | *Clinical signs and epidemiology:
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| − | **Acute disease in susceptible herds with high morbidity and mortality (up to 50%)
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| − | **In acute outbreaks, pigs may be dyspnoeic, pyrexic or anorexic
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| − | **Blood-stained froth surrounding nose and mouth
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| − | **Cyanosis
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| − | **Pregnant sows abort
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| − | **Causes [[Respiratory Bacterial Infections - Pathology#Actinobacillus pleuropneumoniae|pneumonia]] in pigs
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| − | **Carrier herds have some immunity, protecting from acute disease, where lesions are often subclinical, and deaths sporadic
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| − | **Lung scarring and pleural adhesions in many recovered animals
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| − | **Solid immunity develops in recovered animals to all serotypes
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| − | **The disease is spread between herds by carrier pigs
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| − | *Diagnosis:
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| − | **Haemorrhagic consolidation close to the main bronchi and fibrinous pleuritis may be suggestive
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| − | **Specimens are cultured on chocolate agar and blood agar in 5-10% carbon dioxide for 2-3 days
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| − | **Small colonies surrounded by clear haemolysis
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| − | **No growth on MacConkey agar
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| − | **Positive CAMP reaction with [[Staphylococcus spp.|''Staphylococcus aureus'']]
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| − | **Most strains are NAD-dependent (grow on Heated Blood agar)
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| − | **Immunofluorescent- or PCR-based techniques
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| − | **The bacteria on the [[Tonsils - Anatomy & Physiology#Palatine|palatine tonsil]] may remain undetected by serological tests and swabbing, and can therefore cause an outbreak in naive pigs
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| − | *Treatment:
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| − | **Antibiotics depending on the strain of bacteria
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| − | **Prophylactic antibiotics for in-contact pigs
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| − | *Control:
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| − | **Killed and polyvalent bacterin vaccines as well as a subunit vaccine are available
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| − | **Improve ventilation, avoid chilling and overcrowding
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| − | ===''Actinobacillus equuli''===
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| − | *Commensal of the equine intestinal and reproductive tract
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| − | *Pathogenesis and clinical signs:
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| − | **Foals infected ''in utero'' or or after birth via the umbilicus
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| − | **Infection at birth causes severe enteritis and septicaemia within 24 hours, known as sleepy foal disease
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| − | **Foals become pyrexic and recumbent
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| − | **Death usually occurs within 1-2 days
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| − | **In foals that survive neonatal infection the condition progresses to cause joint infections and purulent nephritis, enteritis or pneumonia
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| − | **''A. equuli'' in [[Joints Inflammatory - Pathology#In Horses|arthritis of horses]]
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| − | **Abortion, septicaemia and [[Peritoneal Cavity Inflammatory - Pathology#In horses|peritonitis in horses]]
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| − | *Diagnosis:
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| − | **Specimens cultured on blood agar and MacConkey agar and incubated aerobically for 1-3 days
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| − | **Sticky colonies with variable haemolysis on blood agar
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| − | **Lactose-fermenting colonies on MacConkey agar
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| − | *Treatment and control:
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| − | **Antimicrobials ineffective unless early in course of disease
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| − | **Blood trasfusion and administration of colostrum
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| − | **Good hygiene
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| − | **Consider prophylactic antibiotics for new-born foals
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| − | **Bacteria susceptible to streptomycin, tetracyclines and ampicillin
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| − | *In other animals:
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| − | **Septicaemia in piglets
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| − | **Arthritis and enteritis in pigs
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| − | **Enteritis in calves
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| − | **RTX group cytotoxin present
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| − | ===''Actinobacillus suis''===
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| − | *May be present in upper respiratory tract of sows
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| − | *Pathogenicity and clinical signs:
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| − | **Infection of piglets via aerosol or possibly skin abrasions
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| − | **Fatal septicaemia in piglets 1-8 weeks old
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| − | **Mortality up to 50% in some litters
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| − | **Fever, respiratory distress, prostration and paddling of forelimbs seen in piglets
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| − | **Petechial and ecchymotic haemorrhages in many organs
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| − | **Interstitial pneumonia, pleuritis, meningoencephalitis, myocarditis and arthritis
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| − | **Causes abscesses in joints and lungs of older pigs
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| − | **Carried in the nasopharynx of pigs and nose of horses
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| − | **Carriage may confer immunity to the more severe pleuropneumonia
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| − | *Diagnosis:
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| − | **Specimens cultured on blood agar and MacConkey agar for 1-3 days
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| − | **Sticky haemolytic colonies
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| − | **Pink, lactose-fermenting colonies on MacConkey agar
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| − | *Treatment and control:
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| − | **Bacteria usually susceptible to ampicillin, carbenicillin, potentiated sulphonamides and tetracyclines
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| − | **Disinfect contaminated pens
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| − | *Other animals:
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| − | **Septicaemia and pneumonia in foals
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| − | **Pneumonia in pigs and horses
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| − | ===''Actinobacillus seminis''===
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| − | *Epididymitis in young rams (4-8 months)
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| − | *Polyarthritis in lambs
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| − | *Organism found in prepuce
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| − | *Opportunistic infection causing abscesses in epididymides
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| − | *May be purulent discharge onto scrotal skin
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| − | *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
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| − | ===''Actinobacillus actinomycetemcomitans''===
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| − | *Epididymitis in rams
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| − | [[Category:Bacteria]] | |
