Microbiology
Pathogens
Regarding gas gangrene, which of the following statements is CORRECT:
Answer:
Gas gangrene usually occurs within 3 days of injury, and is characterised by pain, rapidly spreading oedema, myositis, necrosis, palpable crepitus and systemic toxicity. Diagnosis is clinical and laboratory confirmation should not delay urgent surgical intervention. Hyperbaric oxygen therapy can be considered in addition to surgery and antibiotic therapy, to stop toxin production and inhibit bacteria from replicating and spreading (as Clostridium spp. are obligate anaerobes).Clostridium Perfringens
Microbiology / Pathogens / Clostridial Infection
Last Updated: 29th July 2024
| 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.
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 |
