Which of the following types of infection occurs due to superinfection of a gangrenous limb with a gas-forming organism?

Gas gangrene occurs when a limb that is already gangrenous becomes superinfected with gas-forming organisms, particularly from the Clostridium species, such as Clostridium perfringens. This type of infection is characterized by the production of gas within tissues, leading to severe tissue necrosis and rapid deterioration of the affected area. The presence of gas bubbles can be palpated and seen on imaging studies, contributing to the diagnosis of gas gangrene.

In cases of necrotizing fasciitis, while there is a rapid and severe infection of the fascia and subcutaneous tissues, it is not specifically caused by gas-forming bacteria. Cellulitis, on the other hand, is generally a more superficial skin infection without the characteristic gas formation associated with gas gangrene. Furunculosis refers to infections involving hair follicles leading to boils, which are not related to the complications seen in a gangrenous limb or gas production.

Therefore, gas gangrene is the correct answer, as it directly describes the condition resulting from the superinfection of an existing gangrenous site by gas-forming bacteria.