Actinobacillus species

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

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
- 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

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

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
Abortion in mares
Septicaemia in piglets
Arthritis and enteritis in pigs
Enteritis in calves
RTX group cytotoxin present