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

<ncl style=compact maxdepth=4 headings=bullet headstart=2 showcats=1 showarts=1>Category:Clostridium species</ncl>

Enteropathogenic and Enterotoxaemic Clostridia

C. piliforme

• Spore-forming filamentous Gram negative intracellular pathogen
• Only grows in tissue culture or embryonated eggs
• Causes Tyzzer's disease - severe hepatic necrosis
• Sporadic disease in foals, calves, dogs, cats
• Foals under 6 weeks, found dead or comatose
• Incubation period up to 1 week
• Depression, anorexia, fever, jaundice, diarrhoea
• Hepatomegaly and necrosis on post mortem
• Diagnosis: Warthin-Starry silver impregnation technique demonstrates organisms in hepatocytes

C. difficile

• Dogs with chronic diarrhoea
• New born foals with haemorrhagic enterocolitis
• Possibly associated with acute colitis in adult horses following antibiotic therapy or grain overload

C. colinum

• Enteritis in poulty and game birds
• Shed in faeces of clinically affected and carrier birds
• Intestinal ulceration and hepatic necrosis
• Therapeutic antibiotics in drinking water

C. spiroforme

• Spontaneous and antibiotic-induced enteritis in rabbits
• Enterotoxaemia, fatal within 48 hours
• Oral antibiotics upset the intestinal flora, allowing overgrowth of clostridia