Difference between revisions of "Actinobacillus species"

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#REDIRECT[[:Category:Actinobacillus species]]
 
 
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===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 - 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
 
**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
 
**[[Bacterial skin infections - Pathology#Bacterial granulomatous dermatitis|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
 
*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 [[Respiratory Bacterial Infections - Pathology#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'']]
 
**Most strains are NAD-dependent (grow on Heated Blood agar)
 
**Immunofluorescent- or PCR-based techniques
 
**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
 
*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 [[Joints Inflammatory - Pathology#In Horses|arthritis of horses]]
 
**Abortion, septicaemia and [[Peritoneal Cavity Inflammatory - Pathology#In horses|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
 

Latest revision as of 11:12, 10 May 2010