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Title: Studies on the pathogenicity of chitinolytic bacteria isolated from shell disease infected edible crabs, Cancer pagurus
Author: Costa-Ramos, C.
Awarding Body: University of Wales Swansea
Current Institution: Swansea University
Date of Award: 2004
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Bacterial shell disease syndrome, which is characterised by the appearance of black spot lesions on the carapace of affected crustacean species, has been found to affect wild populations of the edible crab, Cancer pagurus, in the Gower region, in South Wales. A previous study isolated nine bacterial isolates (11-19) from lesions of diseased edible crabs. The current study further characterises these isolates and possible modes of action. Pathogenicity studies were performed for all isolates by injection into disease-free crabs and from the initial screening of the nine isolates, two (14 and 17) were studied in further detail due to their high pathogenicity towards edible crabs. These isolates were identified as Stenotrophomonas maltophilia (14) and Pseudoalteromonas atlantica (17). Both caused high mortalities upon injection but with distinct modes of action. S. maltophilia appeared to kill crabs by septicaemia, with bacteria being rapidly removed from the haemocoel, only to reappear close to time of death. Studies with P. atlantica showed that this isolate caused crab mortality as a result of the action of toxic extracellular products (ECP). When injected into crabs these were found to produce the same symptoms as live bacteria (e.g. limb tremors followed by paralysis). Due to the nature of the symptoms, which suggested a neurotoxic action, and due to the heat-stability that the ECP showed, LPS was isolated from live P. atlantica bacteria and from ECP. Such preparations when injected into crabs caused high mortalities and similar symptoms as observed following the challenge with live bacteria or ECP. Overall it was concluded that the main virulence factor of P. atlantica for edible crabs is LPS either alone or in combination with other heat-stable factors. Despite these studies, the potential synergistic roles of these and other bacterial isolates in shell disease syndrome is unresolved.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available