Overview
- Organisms present in the soil, alimentary tract and faeces
- Endospores may be present in liver and may be reactivated to cause disease
- Neurotoxic clostridia, Clostridium tetani and Clostridium botulinum affect neuromuscular function but cause no tissue damage
- Histotoxic clostridia cause localised lesions in tissues and may cause toxaemia
- C. perfringens cause inflammatory lesions in the gastrointestinal tract and enterotoxaemias in sheep
Characteristics
- Large Gram-positive rods
- Obligate anaerobes
- Fermentative, catalase negative, oxidase negative
- Straight or slightly curved
- Motile by flagellae
- Require enriched media for growth
- Produce endospores which vary in shape and location and cause bulging of mother cell
Pathogenesis and pathogenicity
- Produce extracellular digestive enzymes and toxic substance known as exotoxins
- Exotoxins cause necrosis, haemolysis and death
- Collagenase, hyaluronidase and DNase enymes facilitate spread through tissues
Diagnosis
- Anaerobic transport medium
- Culture on blood agar enriched with yeast extract, vitamin K and haemin
- Anaerobic culture with hydrogen supplement and 5-10% carbon dioxide for 48 hours
- Colonies of C. perfringens are 5mm diameter, circular, flat and grey and surrounded by a zone of double haemolysis
- Positive cAMP test with Streptococci agalactiae
- Biochemical tests
- Toxins identified in body fluids by toxin neutralisation or protection tests in lab animals
- Nagler reaction to detect alpha toxin - plate neutralisation test
- Fluorescent antibody tests for histotoxic clostridia
- ELISA, PCR for toxin detection
- Sudden death in unvaccinated farm animals may suggest C. perfringens types B, C and D
- Post mortem
- Gram positive rods present on intestinal smears suggests clostridial enterotoxaemia