Difference between revisions of "Category:Clostridium species"

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