- Cause 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
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
- Commensal in the mouth of sheep and cattle
- Penetrates damaged mucosa to cause a granuloma, a condition known as Actinobacillosis
- Enodogenous, sporadic and chronic 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
- 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
- Recovery with antibiotics
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 arthritis of horses
- RTX group cytotoxin present
Actinobacillus suis
- Fatal septicaemia in pigs 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
Actinobacillus pleuropneumoniae
- Contagious porcine pleuropneumonia
- Endemic in UK
- Most strains are NAD-dependent (grow on Heated Blood agar)
- Positive CAMP reaction
- 12 serotypes causing the same disease
- Different serotypes in different regions, with serotypes 3,6 and 8 the most common in the UK
- Acute disease in susceptible herds with high morbidity and mortality
- 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
- 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
- Produce one or two RTX group cytolytic toxins
- RTX toxins:
- 'Repeat in ToXin' - named because there are 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