Monday, November 21, 2011

Bacteria have survival mode for antibiotic resistance

When bacteria are unable to find enough food to supply them with energy, they are able to switch to a survival mode, which renders them capable of sustaining themselves with far less In addition, bacteria that transform themselves into this low-energy mode are found to have a far greater resistance to antibiotics. While scientists have argued that this is caused by a lack of metabolism needed for the drugs to work, a recent study has shown that this feature is actually acquired by means of an active process. This is an important discovery, because resistance to antibiotics is an emerging problem that renders our drugs ineffective.

Researchers from the University of Washington discovered that bacteria that are unable to send the required chemical warning signals to induce 'starvation mode' are much more sensitive to bacteria that are able to do so. Both types were cultured in a nutrient-deprived medium, which severely slows down the metabolic rate. Because the bacteria in 'starvation mode' are still able to resist antibiotics, it must be attributed to an active protection process induced by the bacterium, instead of merely a lack of metabolism that renders drugs ineffective.

When the scientists experimented to uncover the mechanism behind starvation-induced antibiotic resistance, they found that bacteria are better equiped to protect themselves against oxygen radicals. These chemical compounds damage the cell, and are found in most life forms, including ours. Cells can generate protective chemicals that are dubbed antioxidants, but the scientists did not state whether the starved bacteria produced more of these. It is known that several forms of antibiotics work by inducing a surplus of oxygen radicals, thereby destroying the bacterial cell: this serves as a possible explanation for the resistance in bacteria dormant in survival mode.

The findings are important for treating patients with a bacterial infection. In several diseases, populations of bacteria in survival mode are found, and are therefore able to resist most forms of treatment. With the newly discovered mechanism in mind, treatment can be altered, so that the mode of action involves something else than induction of oxygen radicals. In addition, the findings serve as a new angle for the development of new anti-bacterial compounds. This could save lives, now and in the future, because antibiotic resistance is the cause of more and more deaths each year. 

Groups of starved bacteria are found in various places in the body, such as biofilms (ecosystems of bacteria and their 'homes') and in certain wounds. One of the reason for induction of the survival mode is competition for nutrients: in thick layers, not all of the bacteria are able to reach the food, which sets off the starvation response. It is known that patients with the deadly disease cystic fibrosis have bacterial groups in their lungs that are able to resist treatment. This often results in death, which shows that finding a way to kill this special set of bacteria is much needed.

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