Actinobacillus species

BACK TO INFECTIOUS AGENTS AND PARASITES BACK TO BACTERIA

• Cause peritonitis in horses
• A. pleuropneumoniae causes pneumonia in pigs
• Cause granulomatous inflammation.
  • E.g. Actinobacillus lignieresii causes wooden tongue in cattle -> myositis
• A. equuli in arthritis of horses

Actinobacillus characteristics

• Small Gram negative coccobacilli
• Oxidase negative
• Do not grow on MacConkey

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
• 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
• RTX group cytotoxin present