Gas gangrene

Gas gangrene - Photograph before right leg amputation (hemipelvectomy) of a patient with gas gangrene. The right thigh is swollen, edematous and discoloured with necrotic bullae (large blisters). An impressive crepitation is already palpable. At this juncture the patient is in shock.

 

First of all, I would like to congratulate you for not puking after watching this photo.

How did I get to this picture? I’m having Microbiology 2nd intermediate exam in two days time. It will include

1. Spore forming anaerobes which is mainly the Clostridium species
2. Non-sporing anaerobes
3. Bordetella pertussis
4. Corynebacterium diphteriae
5. Mycobacterium species which are responsible for TB, leprosy and mycobacterioses
6. Antibacterial agents, simply antibiotics

So I was reading about Clostridium pefringens and it says that it causes diseases like food poisoning and also gas gangrene.

I’ve never heard of gas gangrene before but I’ve heard of gangrene, just gangrene, without the word gas in front of gangrene. Then I  Googled for gas gangrene and thats how I got to the photo above. Wikipedia.

Here’s something about Clostridium pefringens:

Diseases:

1. Enteric diseases eg. food poisoning, necrotizing enteritis, antibiotic associated diarrhea AAD, sporadic diarrhea SD
2. Soft tissue infection eg. gas gangrene, cellulitis, fascitis

Symptoms:

1. Gas gangrene: pain, edema, pallor, tenderness, crepitation, jaundice, blood-tinged exudates,hemorrhagic bullae
2. Food poisoning: watery diarrhea, abdominal cramps, vomiting

Pathogenesis:

Gas gangrene

• C.pefringens grow in traumatized tissue/muscle –> produce many toxins like alpha toxin or lecithinase –> damage cell membranes especially of red blood cells’ –> hemolysis
• degradative enzymes–> produce gas

Food poisoning

• enterotoxin as superantigen
• C. pefringens is a member of normal flora in colon –> diarrhea

Epidemiology:

Gas gangrene

• Transmission: from spores in soil, from normal flora of colon and vagina (enter wounds)
• Risk groups: after injury/trauma (accidents, war wounds), after surgery especially of gallbladder & colon, frostbite, open fractures, people with colon cancer

Food poisoning

• spores in soil can contaminate food
• spores are heat-resistant so may survive cooking
• grow to large number in reheated foods

Laboratory diagnosis:

Gas gangrene

• Microscopic exam – gram stain (gram positive) and ink stain
• Anaerobic culture – shows double hemolysis
• PLC test – egg yolk agar is used to demonstrate presence of lecithinase

Food poisoning:

• not usually done
• no assay for the toxin

Treatment:

Gas gangrene

• Penicillin G
• Metronidazole
• Hyperbaric oxygen
• Debride wound

Food poisoning

• symptomatic treatment is given (treatment for diarrhea/vomiting/abdominal pain etc)

Prophylaxis:

Gas gangrene

• clean and debride wound
• Penicillin as prophylaxis before surgery or after getting wound

Food poisoning

• no specific preventive measure
• cook food adequately