Why is it in news?

Adding vitamin C as a nutritional supplement while treating drug-sensitive tuberculosis patients with first-line TB drugs will boost the efficiency of treatment, a study by Indian researchers shows.

Details

• The increase in efficiency is not because vitamin C has antibacterial activity, as was suggested by a few researchers in 2013 from in vitro studies, but by doing the complete opposite — inducing dormancy in TB bacteria.
• A team led by Prof. Jaya Sivaswami Tyagi from the Department of Biotechnology at AIIMS, New Delhi had first proposed the dormancy-inducing ability of vitamin C in TB bacilli in 2010 and has now reconfirmed it in a comprehensive study published in the journal Redox Biology.
• The team found that vitamin C imposes multiple stresses on TB bacteria such as hypoxia, acid stress (where the pH is reduced to around 5.5), oxidative stress (through the generation of H2O2 and reactive oxygen species), reductive stress (due to cessation of aerobic respiration) and metabolic stress. Due to these stresses, there is slowing down of metabolism leading to dormancy and further progression to viable but non-culturable (VBNC) state. Together, these stresses remarkably resemble the host environment that the bacteria would face.
• In the lab, TB bacteria already exposed to vitamin C displayed resistance to two first-line drugs — isoniazid and rifampicin — as it progressed to a dormant state. Unlike these two drugs, pyrazinamide drug is capable of killing TB bacteria even in a dormant state. “The addition of vitamin C increased the population of dormant bacteria and this led to an eight-fold increase in pyrazinamide’s ability to kill the bacteria. There was also a four-fold decrease in the minimum concentration (MIC) of pyrazinamide required to kill the bacteria even in an infection model.
• The effect of vitamin C combined with TB drugs was reproduced in an intracellular model, which is akin to human infection. So, our findings acquire clinical relevance. When used along with other first-line drugs, vitamin C has the potential to shorten the treatment time.
• Besides improving the efficacy of existing TB regimen, vitamin C can help in producing subclasses of bacteria to test new drugs.
• The use of vitamin C can help in producing a population of dormant bacteria which can be used for screening drugs that inhibit efflux pumps.
• Likewise, vitamin C can be used for producing viable but non-culturable (VBNC) TB bacteria.

Conclusion

India has one of the highest burdens of Tuberculosis in the world. Discoveries like these can further help in effectively designing the treatment programmes of the disease. DOTS treatment programme can be tweaked to be more effective using the outcomes of this research. This would help in better recovery rates, lower mortality and reduce India’s TB burden.

Source

The Hindu