Juvenile common thresher sharks (Alopias vulpinus) have been recently stranding throughout the California coast. Necropsy, cytology, bacteriology, and histopathology results, along with microbiome analyses, revealed otitis interna and meningoencephalitis associated with Carnobacterium maltaromaticum infection as the cause of disorientation and stranding deaths. Location and severity of the infection and inflammation suggests that pathogenesis likely involves bacterial entry through the endolymphatic ducts into the inner ear, with subsequent invasion of meninges and brain. Low prevalence of Carnobacterium in the uterine environment of two pregnant females, suggests potential inoculation while in utero. Comparative genomics analysis of nine C. maltaromaticum strains isolated from diseased thresher and salmon sharks (Lamna ditropis) revealed strains of monophylogenetic origin with genomic profiles characteristic of opportunistic pathogens. Signs of genomic degradation and the partial loss of metabolic functions suggest evolution towards a host-adapted pathogenic lifestyle along with the presence of virulence-associated genes that aid in the infection process. Future studies should consider the unique regions found in these strains to identify potential sources of this bacterium in the environment.
|Advisor:||Lowe, Christopher G.|
|Commitee:||Berlemont, Renaud, Dillon, Jesse G., Okihiro, Mark S.|
|School:||California State University, Long Beach|
|School Location:||United States -- California|
|Source:||MAI 58/05M(E), Masters Abstracts International|
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