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Microbiology

Pathogens

Question 3 of 180

Clostridium perfringens primarily causes which of the following infectious diseases:

Answer:

Clostridium perfringens is the most common cause of gas gangrene. C. perfringens is also implicated in food poisoning, cellulitis, enteritis necrotican (life-threatening infection involving ischaemic necrosis of the jejunum), and rarely, CNS infections such as meningitis and encephalitis.

Clostridium Perfringens

Microorganism Clostridium Perfringens
Gram stain Gram positive
Shape Rod
Oxygen requirements Obligate anaerobe
Additional features Spore-forming, Produces exotoxin
Reservoir Soil & intestinal flora
Diseases Gas gangrene, food poisoning

Clostridium perfringens is capsulated and produces a range of exotoxins. It is implicated in gas gangrene and enterotoxin-mediated food-poisoning.

Transmission

It is commonly present in the normal intestinal flora, in faeces and in soil and it may cause endogenous or exogenous infection. Transmission may occur via wound contamination with soil or gastrointestinal contents, or via ingestion of contaminated food.

Clostridial Gas Gangrene

C. perfringens is the most common organism implicated in gas gangrene, although gas gangrene is almost always a polymicrobial infection involving anaerobes and facultative organisms. The condition is prevented by good management of potentially infected, devitalised wounds.

Pathogenesis

Predisposing factors to gas gangrene include:

  • Tissue damage with contamination with clostridial spores and pyogenic organisms
  • Presence of foreign bodies including soil
  • Impaired tissue perfusion with tissue hypoxia
  • Host factors e.g. vascular insufficiency, diabetes mellitus, old age, debility, major surgery to the hip or lower limb

When clostridial infection has been initiated in a focus of devitalised tissue (by germination of clostridial spores), the organisms multiply rapidly and produce a range of exotoxins, resulting in tissue damage and necrosis, creating a more anaerobic environment and further progression of infection.

Clinical Disease

The disease usually occurs within 3 days of injury, and is characterised by:

  • pain in the wound,
  • rapidly spreading oedema,
  • myositis,
  • necrosis of tissues,
  • gas production with crepitus,
  • and profound toxaemia.

By Engelbert Schröpfer, Stephan Rauthe and Thomas Meyer. [CC BY 2.0 , via Wikimedia Commons

Gas Gangrene. (Image by Engelbert Schröpfer, Stephan Rauthe and Thomas Meyer. [CC BY 2.0 , via Wikimedia Commons)

Diagnosis

Diagnosis of gas gangrene is clinical and treatment must not wait for laboratory confirmation.

Management

Management of gas gangrene should involve:

  • prompt and radical surgical debridement of necrotic and devitalised tissue,
  • fasciotomy to release tension,
  • removal of foreign bodies,
  • thorough wound cleansing and packing (wound left open),
  • appropriate antibiotic therapy (e.g. combination of penicillin, gentamicin and metronidazole),
  • and consideration of hyperbaric oxygen therapy.

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  • Biochemistry
  • Blood Gases
  • Haematology
Biochemistry Normal Value
Sodium 135 – 145 mmol/l
Potassium 3.0 – 4.5 mmol/l
Urea 2.5 – 7.5 mmol/l
Glucose 3.5 – 5.0 mmol/l
Creatinine 35 – 135 μmol/l
Alanine Aminotransferase (ALT) 5 – 35 U/l
Gamma-glutamyl Transferase (GGT) < 65 U/l
Alkaline Phosphatase (ALP) 30 – 135 U/l
Aspartate Aminotransferase (AST) < 40 U/l
Total Protein 60 – 80 g/l
Albumin 35 – 50 g/l
Globulin 2.4 – 3.5 g/dl
Amylase < 70 U/l
Total Bilirubin 3 – 17 μmol/l
Calcium 2.1 – 2.5 mmol/l
Chloride 95 – 105 mmol/l
Phosphate 0.8 – 1.4 mmol/l
Haematology Normal Value
Haemoglobin 11.5 – 16.6 g/dl
White Blood Cells 4.0 – 11.0 x 109/l
Platelets 150 – 450 x 109/l
MCV 80 – 96 fl
MCHC 32 – 36 g/dl
Neutrophils 2.0 – 7.5 x 109/l
Lymphocytes 1.5 – 4.0 x 109/l
Monocytes 0.3 – 1.0 x 109/l
Eosinophils 0.1 – 0.5 x 109/l
Basophils < 0.2 x 109/l
Reticulocytes < 2%
Haematocrit 0.35 – 0.49
Red Cell Distribution Width 11 – 15%
Blood Gases Normal Value
pH 7.35 – 7.45
pO2 11 – 14 kPa
pCO2 4.5 – 6.0 kPa
Base Excess -2 – +2 mmol/l
Bicarbonate 24 – 30 mmol/l
Lactate < 2 mmol/l

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