托福考试写作例文7
发布时间：2013/7/17 21:43:52 来源：城市网学院 编辑：admin
Now listen to part of a lecture in a biology class.
As soon as we developed antibiotics, new strains of bacteria appeared that were resistant to some or all of the drugs. Hospitals started using antibiotics regularly in the 1950s, but resistance started appearing within a few years. Today, one-third of the patients in hospitals are on antibiotics, but antibiotic resistance is increasing the danger of hospital infections—to the point where people are almost safer staying home than going to a hospital.
In the forties, penicillin really was a wonder drug. Back then, you could give a patient with bacterial pneumonia ten thousand units of penicillin four times a day and cure the disease. Today, you could give 24 million units of penicillin a day, but the patient might still die. Why? Well, in a way, bacteria are smarter than us. They evolve to counteract any drug we attack them with. A lot of bacteria are now #pletely resistant to penicillin.
Bacteria can evolve very effective weapons against antibiotics. Some of them develop enzymes to match every antibiotic we throw at them. All these weapons and counter-weapons match one another—just like the weapons in real military warfare. So, no matter what antibiotic we use, the bacteria will #e up with a way to make it useless.
How does this happen? Well, if you douse a colony of bacteria with an antibiotic the colony will be killed—that is, all except for a few cells. A few cells will survive because they carry a resistance gene for that particular antibiotic. The surviving cells quickly multiply and they pass along this lucky gene to their offspring. And soon you have a new strain of bacteria that’s resistant to that drug.
One consequence of antibiotic resistance is the reappearance of tuberculosis as a major illness. Twenty years ago, doctors thought tuberculosis was a defeated disease. Since then, however, new cases of tuberculosis have increased by 20 percent. And several strains of the disease are resistant to any drug we can attack them with.
Summarize the main points made in the lecture, explaining how they differ from points made in the reading.
