부산대학교 도서관

Cholera is a persistent threat to public health and is endemic in many countries. Of late, there is an emergence of antibiotic resistance in Vibrio cholerae and treatment is effective only if given early, thus there is a need for rapid and more effective treatment of cholera. One such treatment could be the use of bacteriophages. During infection, V. cholerae adheres to the surface of enterocytes but does not invade the host. They are therefore not protected from bacteriophage infection. The study presented in this dissertation evaluates the potential of bacteriophage being used as a biocontrol for V. cholerae. The aim of this project was isolation and in vitro characterisation of bacteriophages, selection of a candidate bacteriophage for biocontrol and its use in an infant rabbit model to assess its therapeutic efficacy. Seven phages were isolated in China, attempts to isolate in the UK environments were unsuccessful and five more phages were obtained from various sources. In total twelve phages were characterised for the one step growth curves following their host strain growth curves, their lytic spectra, electron microscopy, PFGE, restriction analysis and annotation of sequenced genomes. These in vitro characterisations could help in selecting the candidate bacteriophage for in vivo phage therapy trials. Amongst the phages studied, the phage Φ1 most nearly fitted the selection criteria. Its burst size was 43 ± 5.5; while the latent period was 12 ± 0.0 and it had broad host range as it could lyse 67 % of the total 91 strains; while its genome did not show any undesirable genes associated with lysogeny/antibacterial resistance or any cholera toxin genes upon genome annotation. In therapeutic trials using an infant rabbit model, Φ1 reduced the bacterial numbers significantly (4.7 log10 reduction with P < 0.001) and treated animals showed no symptoms of disease.