Vitamin C could be panacea for drug-resistant TB

Vitamin triggers reaction which eventually kills off bacteria; could help shorten drug therapy

By Kundan Pandey
Published: Wednesday 22 May 2013

TB bacteriaAn unexpected discovery can bring relief to millions of people suffering from multi-drug resistant tuberculosis (MDR-TB) across the globe. A study by an American research team reports that vitamin C can kill the bacteria Mycobacterium tuberculosis that causes MDR-TB.

The report published on Tuesday says, “Vitamin C, a compound known to drive the Fenton reaction, sterilizes cultures of drug-susceptible and drug-resistant Mycobacterium tuberculosis, the causative agent of tuberculosis.”

Researchers at the Albert Einstein College of Medicine, New York, found that the vitamin C effectively kills drug-resistant TB bacteria under laboratory conditions. It also suggests that vitamin C can shorten the duration of drug therapy.

Domino effect

In a statement, the college mentioned that the discovery was made during research into how TB bacteria become resistant to isoniazid, a potent first-line TB drug. The research team observed that isoniazid-resistant TB bacteria were deficient in a molecule called mycothiol.

Drug resistance decoded
Multi-drug-resistant TB (MDR-TB): TB that does not respond to isoniazid and rifampicin, the two most potent anti-TB drugs

Extensively drug-resistant TB (XDR-TB): TB that is resistant to rifampicin and isoniazid, as well as to any member of the quinolone family of antibiotics and at least one of four second-line injectable anti-TB drugs
“We hypothesized that TB bacteria that can’t make mycothiol might contain more cysteine, an amino acid,” says William Jacobs, lead investigator and senior author of the study.  “So, we predicted that if we added isoniazid and cysteine to isoniazid-sensitive M. tuberculosis in culture, the bacteria would develop resistance. Instead, we ended up killing off the culture— something totally unexpected,” he says.

The research team suspected that cysteine was helping kill TB bacteria by acting as a reducing agent that triggers the production of reactive molecules containing oxygen, sometimes called free radicals. These highly reactive molecules can react with and damage important cellular components like DNA, and can thus cause the ageing and death of cells.

"The combination of isoniazid and vitamin C sterilised the M tuberculosis culture. We were then amazed to discover that vitamin C by itself not only sterilised the drug-susceptible TB, but also sterilised MDR-TB and XDR-TB strains," says Jacob. Vitamin C induced what is known as a Fenton reaction, causing iron to react with other molecules to create the reactive oxygen species that kill the TB bacteria.

In 2011, TB affected some 8.7 million people and cost about 1.4 million lives, according to the World Health Organization (WHO). Infections that fail to respond to TB drugs are a growing problem. About 650,000 people worldwide now have multi-drug-resistant TB (MDR-TB), nine per cent of who have extensively drug-resistant TB (XDR-TB).TB is especially acute in low- and middle-income countries, which account for more than 95 per cent of TB-related deaths, according to WHO.
The study, titled Mycobacterium tuberculosis is extraordinarily sensitive to killing by a vitamin C-induced Fenton reaction, was published in online journal Nature Communications on Tuesday.


Global tuberculosis report 2012

Totally drug-resistant tuberculosis (TDR-TB) in India: every dark cloud has a silver lining

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