Evaluation of Therapy with Hyperbaric Oxygen for Experimental Infection with

The effects of inoculum size and treatment delays on the efficacy of hyperbaric oxygen (HBO) were evaluated in a murine model of Clostridium perfringens myositis in which the infection was treated with an HBO regimen identical to that used for humans. The efficacies of treatment with penicillin, metronidazole, or clindamycin—alone or in combination with HBO—were also as-sessed. Survival was inversely related to the size of the bacterial inoculum used for challenge, and delays in treatment markedly reduced the efficacies of all single and combination regimens. When animals were challenged with>10 8 colony-forming units, survival was significantly higher among those treated with clindamycin or metronidazole than among those treated with penicil-lin. HBO alone did not improve survival at any inoculum tested. However, when administered early, HBO plus metronidazole or penicillin demonstrated significant additive efficacies in ani-mals challenged with-10 9 organisms. Clindamycin was more effective at the higher inocula than penicillin, metronidazole, or HBO, and its superior efficacy was not further enhanced by adjunc-tive therapy with HBO. Gas gangrene caused by Clostridium perfringens is a fulmi-nant infection that rapidly progresses to profound shock an