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In the fast proliferating malignant tumors which are characterized by abnormal vascularisation develop non oxidized regions of a low oxygen partial pressure (pO2). Because these tumors are unsusceptible to a conventional therapy they were chosen for clostridial therapeutic gene strategies. There were presented different strategies using clostridia as selective vectors of destructive genes, e.g. cytosine deaminase and nitroreductase activating in reduced microenvironment of tumors--nonactive prodrugs towards strong cytostatics, destroying hypoxic tumor cells. In general, they form a basis for CDEPT strategy (clostridial-directed enzyme prodrug therapy) and moreover in connection with antivessel cytostatic they form COBALT strategy (combination bacteriolytic therapy). In another strategy genetically modified clostridia are transferred to the gene of TNF alpha cytokine which production regulates fractionated ionizing radiation activating a promoter include in the clostridial vector. Sat last, there were discussed new problems connected with clostridial therapeutic gene strategies.

This review describes the subject of clostridial complications in leukemia and malignant neoplasms. These complications include bacteremia and spontaneous nontraumatic gas gangrene of the muscles. The mechanism of anaerobic microenvironment formation, which is necessary for infection development in neoplastic tumors, is also demonstrated. The role of risk factors contributing to the occurrence of clostridial infections is discussed. Further, the etiology of infections, related mostly to the action of Clostridium septicum and Clostridium perfringens toxins, as well as the pathogenesis of complications and their clinical course are indicated. Present treatment strategies are also briefly described.