Acetic acid, an active ingredient in vinegar, can be used as an inexpensive and non-toxic disinfectant against drug-resistant tuberculosis (TB) bacteria, scientists say.Acetic acid can effectively kill mycobacteria, even highly drug-resistant Mycobacterium tuberculosis, according to an international team of researchers from Venezuela, France, and the US. Work with drug-resistant tuberculosis bacteria carries serious biohazard risks.
Chlorine bleach is often used to disinfect TB cultures and clinical samples, but bleach is toxic and corrosive, researchers said. Other effective commercial disinfectants can be too expensive for TB labs in the resource-poor countries where the majority of TB occurs, they said.
"Mycobacteria are known to cause tuberculosis and leprosy, but non-TB mycobacteria are common in the environment, even in tap water, and are resistant to commonly used disinfectants," said Howard Takiff, senior author on the study and head of the Laboratory of Molecular Genetics at the Venezuelan Institute of Scientific Investigation (IVIC).
While investigating the ability of non-TB mycobacteria to resist disinfectants and antibiotics, Takiff's postdoctoral fellow, Claudia Cortesia stumbled upon vinegar's ability to kill mycobacteria. Testing a drug that needed to be dissolved in acetic acid, Cortesia found that the control, with acetic acid alone, killed the mycobacteria she wanted to study.
"After Claudia's initial observation, we tested for the minimal concentrations and exposure times that would kill different mycobacteria," said Takiff. Collaborators Catherine Vilcheze and William Jacobs, Jr at the Albert Einstein College of Medicine in New York tested TB strains and found that exposure to a 6 per cent solution of acetic acid for 30 minutes effectively kills tuberculosis, even strains resistant to almost all antibiotics. In other words, exposure to 6 per cent acetic acid, just slightly more concentrated than supermarket vinegar, for 30 minutes, reduced the numbers of TB mycobacteria from around 100 million to undetectable levels, researchers said. Takiff also tested how effective acetic acid was against M abscessus, one of the most resistant and pathogenic of the non-TB mycobacteria.
He found that M abscessus required exposure to a stronger 10 per cent acetic acid solution for 30 minutes to be effectively eliminated. The team also tested the activity under biologically 'dirty' conditions similar to those encountered in clinical situations, by adding albumin protein and red blood cells to the acetic acid and found it was still effective. "There is a real need for less toxic and less expensive disinfectants that can eliminate TB and non-TB mycobacteria, especially in resource-poor countries," said Takiff. The study is published in mBio, the journal of the American Society for Microbiology.