US scientists have uncovered a defence mechanism¹ in bacteria that allows them to fend² off the threat of antibiotics⁴.

美国科学家发现细菌的防御机制，可以使其低档抗生素的威胁。

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MRSA highlights the problem of antibiotic resistance

It is hoped the findings could help researchers boost the effectiveness of existing treatments.

The study published in Science found that nitric oxide⁵（氧化一氮） produced by the bacteria eliminates some key effects of a wide range of antibiotics（抗生素）.

One UK expert said inhibiting⁶ nitric oxide synthesis（合成，综合） could be an important advance for tackling tricky⁷ infections.

Antibiotic resistance, for example with MRSA, is a growing problem and experts have long warned of the need to develop new treatments.

The latest research, done by a team at New York University, showed that in bacteria the production of nitric oxide - a small molecule⁸ made up of one nitrogen and one oxygen atom - increased their resistance to antibiotics.

They found the enzymes¹⁰（酵素） responsible for producing nitric oxide were activated¹¹ specifically in response to the presence of the antibiotics.

They also showed that nitric oxide alleviates¹²（减轻，缓和） damage caused by the drugs as well as helping¹³ to neutralise many of the toxic¹⁴（有毒的） compounds within the antibiotic.

The researchers then showed that eliminating nitric oxide production in the bacteria allowed the antibiotics to work at lower, less toxic doses.

More effective

Study leader, Dr Evgeny Nudler, said developing new medicines to fight antibiotic resistance, such as that seen with MRSA is a "huge hurdle¹⁵（障碍）".

"Here, we have a short cut, where we don't have to invent new antibiotics.

"Instead we can enhance the activity of well-established ones, making them more effective at lower doses.

Dr Matthew Dryden, consultant¹⁶ in microbiology and communicable disease at Royal Hampshire County Hospital and general secretary of the British Society for Antimicrobial Chemotherapy, said if the enzyme⁹ which creates nitric oxide could be inhibited¹⁷（羞怯的，内向的）, it could suppress the ability of the bacteria to counteract¹⁸（抵消，阻碍） antibiotics.

"This would be a useful therapeutic¹⁹（治疗的） advance, especially as we are running out of new classes of antibiotics and there is less antibiotic development in general."