Decreased resistance of multiresistant mycobacteria to isoniazid during the treatment of experimental tuberculosis with ozone and isoniazid

Mycobacteria (MB) of the clinical strain resistant to streptomycin, isoniazid (IN), rifampicin and kanamycin were injected intravenously into 68 BALB/c mice. The animals were divided into 5 groups: two control groups 0 and 1 (intact and infected without subsequent treatment), group 2 (treated with IN), group 3 (treated with IN and injected intraperitoneally with dissolved ozone, or dO3), group 4 (injected with dO3). The animals started to die by month 4 after the infection. By month 5 all mice died with the exception of intact mice and those treated with dO3). By month 4 the study of MB cultures isolated from the lungs revealed a decrease in their resistance to IN in the groups undergoing treatment with dO3. Hepatic and splenic lesions were observed after treatment with IN only were greater than in the absence of treatment. After the use of IN + dO3 such lesions were the least. The mechanism of a decrease in the medicinal resistance of MB under the action of dO3 and the expediency of the simultaneous use IN and dO3 in cases of the unknown medicinal resistance of MB are discussed.     

Mechanisms of action of isoniazid

For decades after its introduction, the mechanisms of action of the front-line antituberculosis therapeutic agent isoniazid (INH) remained unclear. Recent developments have shown that peroxidative activation of isoniazid by the mycobacterial enzyme KatG generates reactive species that form adducts with NAD(+) and NADP(+) that are potent inhibitors of lipid and nucleic acid biosynthetic enzymes. A direct role for some isoniazid-derived reactive species, such as nitric oxide, in inhibiting mycobacterial metabolic enzymes has also been shown. The concerted effects of these activities - inhibition of cell wall lipid synthesis, depletion of nucleic acid pools and metabolic depression - drive the exquisite potency and selectivity of this agent. To understand INH action and resistance fully, a synthesis of knowledge is required from multiple separate lines of research - including molecular genetic approaches, in vitro biochemical studies and free radical chemistry - which is the intent of this review.