Development of intergrative technology for gene inactivation in Clostridium difficile

目前，公众对英国医院感染率的担忧加剧，特别是那些由所谓的超级细菌引起的感染，这些超级细菌已经对现有的抗生素产生了抗药性。艰难梭菌是一种高度耐药的细菌，是住院患者感染的主要原因。它会导致虚弱的腹泻，在极端情况下可能会导致死亡。目前，只有两种抗生素可用于治疗这种疾病，甲硝唑和万古霉素。这种疾病主要影响老年人。因此，80%的病例发生在65岁以上的人群中。随之而来的是，随着英国65岁以上人口比例的增加，这种疾病变得越来越常见。除了它造成的人类痛苦外，艰难梭菌的爆发还花费了国家卫生服务机构相当大的一笔钱。这主要是因为受感染的患者需要长时间住院。去年英国有28,819个病例，据估计，NHS每年要花费超过1.15亿英镑。此外，如果出现对甲硝唑和万古霉素耐药的菌株，情况可能会升级到失控状态。需要更有效的方法来预防这种疾病。为了控制感染，医学科学了解生物体如何导致疾病是至关重要的。在Wellcome Trust的赞助下，这种生物体的完整基因组序列(即其基因蓝图)现在已经在剑桥的桑格研究所确定。然而，尽管我们现在知道艰难梭菌染色体中每个基因的精确序列，但在大多数情况下，我们并不了解它们的确切功能。弄清楚单个基因的作用的最有效方法是突变它们(使它们失去功能)并评估后果。这种方法目前对这种细菌是不可能的，因为研究科学家无法获得导致目标基因特定突变所需的遗传工具。开发这些突变工具是本提案的总体目标。它们的可获得性应该能够识别感染所需的那些基因，这最终应该会导致更有效地控制疾病的方法。

There are currently heightened public concerns over infection rates in UK hospitals, and in particular those caused by so called superbugs that have become resistant to available antibiotics. The bacterium Clostridium difficile is a highly resistant bug that is a major cause of infections in hospitalised patients. It causes debilitating diarrhoea, which in extreme cases can cause death. Currently, only two antibiotics are available for treating the disease, metranidizole and vancomycin. The disease mainly affects old people. Thus 80 per cent of cases occur in the people who are over the age of 65. It follows, that as the proportion of the UK population that is over 65 is increasing, the disease is becoming more common. Aside from the human suffering it causes, outbreaks of C. difficile cost the National Health Service considerable sums of money. This is mainly because infected patients need to stay in hospital for extended periods of time. With 28,819 cases in the UK last year, it can be estimated to be costing the NHS over 115 million pounds per year. Moreover, there is a danger that the situation could escalate out of control should strains resistant to metranidizole and vancomycin emerge. More effective ways of preventing the disease are required. To control infections, it is crucial that medical science understands how an organism causes disease. Under Wellcome Trust sponsorship, the complete genome sequence of the organism (i.e. its genetic blueprint) has now been determined at the Sanger Institute, Cambridge. However, whilst we now know the precise sequences of every gene in the C. difficile chromosome, in the majority of cases we do not understand their precise function. The most effective method of working out what individual genes do, is to mutate them (make them non-functional) and assess the consequences. Such an approach is not currently possible with this bacterium because the genetic tools necessary to bring about the specific mutation of target genes are not available to the research scientist. The development of these mutational tools is the overall goal of this proposal. Their availability should allow the identification of those genes which are required for infection, which should eventually lead to more effective ways of controlling the disease.