Another reason to eat more citrus fruits. Vitamin C boosts efficacy of TB drugs

Giving vitamin C with tuberculosis drugs could reduce the unusually long time it takes these medicines to eradicate the deadly pathogen, a study suggests.

Researchers at Albert Einstein College of Medicine in the US treated Mycobacterium tuberculosis-infected mice with anti-tuberculosis drugs or vitamin C alone, or the drugs and vitamin C together. They measured M tuberculosis (Mtb) organ burdens at four and six weeks post treatment.

Vitamin C had no activity by itself, but in two independent experiments, the combination of vitamin C with the first-line TB drugs, isoniazid and rifampicin, reduced the organ burdens faster than the two drugs without vitamin C.

Experiments in infected tissue cultures demonstrated similar results, shortening the time to sterilisation of the tissue culture by seven days, researchers said.

“Our study shows that the addition of vitamin C to TB drug treatment potentiates the killing of Mtb and could shorten TB chemotherapy,” said William R Jacobs, principal investigator of the research published in the journal Antimicrobial Agents and Chemotherapy.

That is important because treatment of drug susceptible tuberculosis takes six months, “resulting in some treatment mismanagement, potentially leading to the emergence and spread of drug-resistant TB,” said Jacobs.

Such long-term treatment is needed for tuberculosis because a subpopulation of Mtb cells can form Mtb persister cells, dormant cells that are virtually impervious to antimicrobials, researchers said.

In earlier studies, the investigators discovered that while high levels of vitamin C will kill actively dividing cells, lower concentrations will stimulate respiration and prevent the formation of persisters, said Jacobs. Then, in the presence of TB drugs, that increased respiration will lead to rapid death of the cells.

“Thus in our new paper, we postulate that vitamin C is stimulating respiration of the Mtb cells in mice, thus enabling the action of isoniazid and rifampicin,” said Jacobs.

Tuberculosis is a major worldwide public health problem, infecting the lungs and other organ systems, researchers said. In 2016, the disease sickened more than 10 million people worldwide, and killed 1.7 million, they said.

Treatment of multi-drug resistant TB takes at least two years, and requires use of toxic second-line TB drugs with severe side effects.