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  3. The Struggle Against SuperbugsA Rarely does a bacterium be

The Struggle Against SuperbugsA Rarely does a bacterium be

游客2024-01-09  8
问题                     The Struggle Against Superbugs
A  Rarely does a bacterium become the fuel for a national election campaign. Staphylococcus aureus, though, won just such a dubious distinction earlier this year when a drug-resistant form known as MRSA became a byword for the filthy state of British hospitals. As ever, the truth is more prosaic than election hype. MRSA is a global problem, as indeed is the rise of other drug-resistant "superbugs". Science  is struggling to cope. There are too few new antibiotics in the pipeline and hopes were dashed this week that a vaccine against S.aureus might be developed soon.
B  Three billion years of evolution have turned S.aureus into a pretty mean bacterium. Although it is found on human skin, its preferred habitat is up the nose. When it gets inside the body, it can manifest itself as anything from harmless, pimples to life-threatening diseases, such as endocarditis (inflammation of the heart tissue) and septicaemia. The over use of antibiotics in the past fifty years means that S.aureus is now resistant to treatment. In America alone, every year 2 million people acquire bacterial infections while in hospital and 90,000 of them die as a result, according to the Centres for Disease Control and Prevention in Atlanta. The methicillin-resistant strain of S.aureus, MRSA, is of particular concern. Infections are a growing global problem.
C  First spotted in 1961, MRSA is now endemic in many hospitals. In many Asian countries 70-80% of the strains isolated from diseased tissue have the MRSA form of S.aureus. In America, the figure is around 40%. In Britain, the percentage of death certificates mentioning it as a factor contributing to death has shown a staggering rise since 1993. The disease is also hyper- endemic in Italy, Turkey and Argentina. In a study published earlier this year, among 500 otherwise healthy children attending a hospital outpatient clinic in Nashville, 9.2% had MRSA up their noses. The same study three years earlier had put this figure at 0.8%.
D  According to the Lancet, countries that have more or less ignored MRSA, such as China, South Korea and Japan, have some of the highest rates of incidence. Meanwhile, those with a low prevalence of MRSA, such as Finland, Denmark and the Netherlands, have high levels of surveillance and strictly enforced contact precautions. The bug’s spread can be greatly reduced by scrupulous hygiene. Hospitals in the Netherlands isolate patients with MRSA and screen everyone who comes into contact with them. Once a patient has become iii with MRSA, there are only a few expensive antibiotics left that can treat it. Strains resistant to these are already emerging. It is a war between man and a bacterium, and the outcome is by no means certain.
E  Many people believe that the main stumbling block is a lack of new antibiotics. Fewer and fewer antibiotics are being discovered. Richard Wise, who chairs the committee on anti-microbial resistance for the Department of Health in Britain, is one of many who are concerned. Of those few new drugs that have emerged, he says, most are not sufficiently novel to combat resistance to old drugs. Antibiotics are not big earners for the pharmaceutical companies. Drugs for chronic conditions are far more profitable because they keep working and remain saleable, unlike antibiotics. In December this year, the British Department of Health will bring industry and academia together to try to address some of these problems in Europe. It won’t be easy. Most drug companies have cut back on their efforts. An American study last year found that out of 506 drugs in development, only five were new antibiotics.
F  Others think that vaccines might be the answer. As antibiotics attack bacteria directly, this leads to an evolutionary pressure on the bacteria to evade this. Vaccines stimulate the body to mount its own, far more deft, defences. According to Alison Holmes, director of infection control and prevention at Hammersmith Hospital in London, because vaccines reduce infection in the first place, they cut the volume of antibiotics used to treat the infection and thus would slow down the emergence of new superbugs.
G  Two companies are working on a vaccine that, in theory, would work against S.aureus. Such a vaccine could be used in one of several ways. It might be given to people who were about to undergo an invasive procedure or operation, such as cardiac surgery, which would reduce the risk of complications and need for antibiotics. Or, if the vaccine were long lasting, it might be given to people who were at a continuing risk from S.aureus infection, such as those undergoing kidney dialysis. Vaccine Research International (VRI), a small private company based in Birmingham, is about to end the first phase of a clinical trial of a vaccine aimed at Staphylococcal infections. It hopes the drug, based on a whole but inactivated organism, might be used to address the problem of infections in joint-replacement patients. The results are due in January next year.
H  Nabi Biopharmaceuticals, based in Rockville, Maryland, is further ahead with its trials. Until this week, Nabi had hoped to launch its vaccine, initially for dialysis patients, in Europe in 2006, subject to a final confirmatory clinical trial. Unfortunately, on November 1st, Nabi was forced to halt work when it failed to confirm an earlier confirmatory clinical trial that showed it protected these patients. This is not necessarily the end of the road. The problem may be a glitch in production, or the difficulties of immunising dialysis patients whose underlying conditions mean they often have weakened immune systems. Nabi says it pushed ahead with the vaccine for this group first because the clinical need was so great. Other groups of patients may be able to produce a better immune response to the vaccine.
I  The Nabi vaccine is only a portion of the actual bacterium attached to a carrier protein that stimulates the immune system. Judith Davies, a spokesperson for Vaccine Research International, argues that the history of vaccines shows that more broad-ranging and longer lasting immunity  tends to come from vaccines based on complete organisms, such as the one developed by her company. Nabi disagrees, but even if the halting of its trials is later attributed to a trivial problem, it will take several years to get to this stage again. It remains to be seen whether a vaccine against MRSA can be developed. Vaccinating against bacterial pathogens, rather than treating them with antibiotics, is a promising route forward. If they can be made to work, prevention would be, as ever, better than cure. [br] *
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