Three-year-old Jack has been up half the night, screaming with pain. Now, he is in the doctor's surgery, where his GP reports that Jack's eardrum is red and inflamed. The little boy's mum is pleased because that means the doctor will prescribe an antibiotic(抗菌素). And that means that Jack will get better very soon. Most of us, adults and children alike, are comfortable with antibiotics. While no one denies that many family doctors prescribe antibiotic too freely, huge quantities of the drugs are pumped into patients before, during and after surgery to prevent infection. About 70 million presciptions for them are written each year in England and Wales—the equivalent of dosing(剂量) every man, woman and child with one-and-a-half courses. We take them for everyday ailments such as acne(粉刺), infected cuts, dental abscesses(脓肿) and so on. We see them as an essential safety net to prevent a trivial complaint turning serious. But now! Everything we thought we knew. about antibiotics is being challenged by the experts. Dr. Gruneberg says: Even when the cause is bacterial, there is often no need for treatment because we can use our natural defence systems to fight Off the illness. But ills not just unnecessary prescriptions which cause problems. Apparently the actual courses of antibiotics are longer than necessary, increasing the risks of resistance to the drugs. Dr. Andrew Swan, a consultant microbiologist in Leicester, says: 'If you have recovered from your infection after a couple of days of treatment, and it wasn't too serious in the first place, carrying on with the tablets is adding to the problems of resistance.' Dr. Swan is also concerned about the growing popularity of the newer broad-spectrum antibiotics (谱抗菌素 ), which can kill a wide range of bacteria. He explains: 'The more bacteria killed off, the greater the risk that the treament will chase off harmless organisms and allow those which are resistant to drugs to multiply.' From the passage we can learn that ______.