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Ask the doctors: Dr Luisa Dillner

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Ask the doctors: Dr Luisa Dillner

If you caught pneumonia in the pre-antibiotic era, you had only a 50 per cent chance of surviving. So it is no wonder that England's chief medical officer, Professor Sally Davies, is anxious that antibiotics don't lose their effectiveness. Last month, she warned that bacteria are becoming increasingly resistant to antibiotics. If this carries on, we will no longer have cures for common infections. Each year, about 25,000 people in Europe die from antibiotic-resistant infections.

But this isn't new. Since 1961, has been resistant to penicillin and has caused serious illness (pneumonia and skin sepsis). Methicillin-resistant is a real problem in hospitals, and there have been community outbreaks.

Different antibiotics kill bacteria in various ways. They may destroy cell walls, stop protein production, or prevent them from copying their DNA so they can't reproduce. Bacteria can evade destruction through random changes (and there is evidence that even before penicillin was discovered, some bacteria, through spontaneous mutations, were already resistant to it), or by picking up new genetic material from other bacteria. These resistant bacteria learn to deactivate antibiotics or to continue to grow despite them.

Resistance is fuelled by many things. Overprescribing is a major factor - by being constantly exposed to antibiotics, some bacteria learn how to avoid being killed - only take these drugs if you really need them. One-third of the public wrongly believe antibiotics can cure colds, but colds are caused by viruses, not bacteria.

Most antibiotics are given by doctors for upper respiratory tract infections "just in case". The patient is unlikely to need them, but the doctor wants to play safe in case the infection turns out to be bacterial rather than viral (tests to prove what bug causes common infections take a while and are usually not worth doing). Nor do we need antibiotics for most sore throats, coughs or earaches, and definitely not for flu.

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