This dissertation. reports the first detailed study of the
possible pathogenic mechanisms and virulence determinants of the
fish pathogen V. anguillarum carried out in association with histo-pathological
studies using electron microscopy and electrocardiography
In addition, possible infection route (s) were investigated and the
effect of environmental variables on pathogenesis examined.
Pathogenicity was found to be species specific with strains
which were avirulent in eels being highly virulent in grey mullet.
Following injection of virulent bacteria into eels all tissues were
rapidly colonised, death being characterised by severe haemorrhagic
septicaemia. In contrast, avirulent strains were rapidly eliminated
from the eel host to levels below detection. The heart was particularly
affected during pathogenesis. Vibriosis was found to be temperature
related, disease being retarded by low temperature.
Pathogenic properties investigated included production of
enzymes and haemolysins and examined in vitro phagocytosis and
growth rates. Membrane proteins were extracted by various techniques
and separated using SDS-polyacrylamide electrophoresis thereby
elucidating interstrain variation in protein profile, most strains
containing a major outer membrane protein thought to be a porin.
Ultrastructural studies revealed some bacteria to have up to three
polar flagella per cell, with multiflagellate forms only being
observed in virulent strains. Analysis of plasmid DNA revealed a
partial correlation between possession of a 47 megadalton plasmid
and colistin resistance.
Experimental vibriosis was characterised by deposition of
haemosiderin in liver tissues, thought to be a poorly studied host
defence mechanism, and large numbers of tissue bacteria surrounded
by an electron lucent zone which was non-capsular in nature. Features
of the disease included desquamation of the intestinal mucosa with
excessive loss of ions into the gut lumen.
The most likly route of infection was thought to be via the
gut, as osmoregulatory processes provided a direct means for waterborne
V. anguillarum to enter the gut, to which this bacterium was
found to be particularly well adapted. Gut traversal was thought to
be the precursor to a possible latent infection in the kidney.
Date of Award | 1981 |
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Original language | English |
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Awarding Institution | |
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PATHOGENICITY OF VIBRIO ANGUILLARUM IN FISH
CHART, H. (Author). 1981
Student thesis: PhD