Identification and characterisation of the phage and host receptors in Clostridium difficile, a prerequisite for future phage therapies.

艰难梭菌（Clostridium difficile）是医院获得性腹泻和抗生素相关性腹泻的主要感染原因，在美国和欧洲，每年分别有超过50万和40万例艰难梭菌感染（CDI）新病例。CDI管理的成本相当高，目前用于治疗感染的少数抗生素由于越来越多的耐药艰难梭菌分离株的报告而受到损害。需要替代疗法。一个特别有前途的策略是噬菌体疗法。许多艰难梭菌噬菌体已被分离出来，但迄今为止它们都是温带的。虽然这排除了传统的噬菌体治疗（需要裂解噬菌体），但这种溶原噬菌体是递送致命货物的理想策略，例如针对溶原宿主的CRISPR/Cas9阵列。例如，将携带针对毒素基因的CRISPR阵列的修饰噬菌体口服到微生物组中，将消除所有易感的艰难梭菌菌株。这种方法的一个障碍是迄今为止分离的艰难梭菌噬菌体的宿主范围狭窄。虽然这可以通过合理的工程来克服，以扩大噬菌体宿主范围，但对噬菌体或宿主细胞受体的身份知之甚少。收集这些信息是这个博士项目的目标。这个项目的结果将是噬菌体和宿主细胞受体多达四个噬菌体的身份的派生和它们相互作用的性质有了更深入的了解。这些数据将为噬菌体的后续工程设计奠定基础，以扩大其宿主范围，提高其治疗潜力。

Clostridium difficile is the leading infective cause of hospital-acquired and antibiotic-associated diarrhoea with over 500,000 and 400,000 annual new cases of C. difficile infection (CDI) in the US and Europe, respectively. The cost of CDI management is considerable and those few antibiotics currently used to treat infections are compromised by increasing reports of antimicrobial resistant C. difficile isolates. Alternative therapies are required. One particularly promising strategy is phage therapy. Numerous C. difficile phages have been isolated, but to date they are all temperate. Whilst this rules out conventional phage therapy (lytic phage required), such lysogenic phage are ideal for strategies that deliver a lethal cargo, such as a CRISPR/Cas9 array targeted against the lysogenized host. Oral delivery to the microbiome of a modified phage carrying a CRISPR array directed against a toxin gene, for instance, would eliminate all susceptible C. difficile strains. An impediment to this approach is the narrow host range of C. difficile phages isolated to date. Whilst this could be overcome by rational engineering to broaden phage host range, little is known of the identity of either phage or host cell receptors. Gathering this information is the objective of this PhD project. The outcome of this project will be the derivation of the identity of the phage and host cell receptor for up to four phage and a greater understanding of the nature of their interaction. The data will lay the foundation for the subsequent engineering of phage to broaden their host range and increase their therapeutic potential.