A 62-year-old diabetic black man presents in the emergency room with a swollen l

Question

A 62-year-old diabetic black man presents in the emergency room with a swollen left leg with areas of blanching and dark colored mottling. A "foul odor" is coming from a dressed wound. The physicians remove the dressing and a brownish fluid is seeping from a wounded area. The fluid contains what appear to be small bits of the tissue. No pus appears to be present. The wound has a strong "rotten" odor.

Five days earlier, while at his work as a farmer, he caught the leg in his hay and soil spreader, sustaining a deep, crushing, grossly dirty injury. His wife cleaned the wound as well as she could with soap and water, dressed it with clean gauze, and wrapped it tightly with an elastic bandage to stop the bleeding. The second day they redressed the wound and applied triple antibiotic ointment. The patient treated his pain with ibuprofen (Advil). He reported the pain was not very bad for the first 72 hours. In the past 24 hours, the leg swelled and the mottling began to appear. A foul odor and severe pain accompanied the swelling. His wife convinced him to come to the emergency room even though they did not have medical insurance.

THE QUESTION:

Please make a determination of the disease and the causative agent. Include the factors that lead you to the determination.

Explanation / Answer

This patient has gas gangrene. Gas gangrene is caused by the bacteria of the genus Clostridium. Clostridia are a type of infection-causing bacteria that grow in absence of oxygen. Specifically, this patient must have been infected by Clostridium perfringens which is found universally in the soil and manure (he became infected by the Clostidia when he got his leg caught in a soil spreader). During an immune response, there are cells that come out of the blood to clean up the wound, these cells bring liquid with them (the brownish fluid). As Clostridia grow, they produce poisonous toxins and gas (causes swelling and mottling) in body tissues that damages tissues (this is why small bits of tissue is found in the fluid). Drainage from the tissues will create a foul-smelling brown-red or bloody fluid (serosanguineous discharge). Serosanguineous discharge comes from the body's attempt to heal the wound. The foul smell comes from the Clostridia producing end products such as butyric acid, acetic acid, butanol and acetone, and large amounts of gas (CO2 and H2) during growth, these compounds formed give off a very foul smell.

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