Importance of a siderophore in the pathogenesis and virulence of Photobacterium damsela subsp. pisci...

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" Importance of a siderophore in the pathogenesis and virulence of Photobacterium damsela subsp. piscicida in hybrid striped bass (Morone saxatili x Morone chrysops) "
J. P. Hawke R. L. Thune

Document Type	:	Latin Dissertation
Language of Document	:	English
Record Number	:	1113091
Doc. No	:	TLpq304245223
Main Entry	:	J. P. Hawke
	:	R. L. Thune
Title & Author	:	Importance of a siderophore in the pathogenesis and virulence of Photobacterium damsela subsp. piscicida in hybrid striped bass (Morone saxatili x Morone chrysops)\ J. P. HawkeR. L. Thune
College	:	Louisiana State University and Agricultural & Mechanical College
Date	:	1996
student score	:	1996
Degree	:	Ph.D.
Page No	:	155
Abstract	:	Photobacterium damsela subsp. piscicida, formerly Pasteurella piscicida, is an important new pathogen of hybrid striped bass cultured in brackish water on Louisiana mariculture farms. Louisiana isolates compared with strains of P. damsela subsp. piscicida from Greece, Japan, Israel and Chesapeake Bay, USA and were found to be identical in biochemical phenotype and enzymic activity. Small plasmids of 8 and 5 kb were unique to Louisiana strains. Sequential daily bacteriology and histopathology on hybrid striped bass experimentally infected by immersion revealed that following high doses (13,000 CFU/ml) the gills and spleen are colonized first as early as 24 hours PI, followed by the blood at 48 hours and the liver at 72 hours. Bacteria reached levels as high as usd5.7\times10\sp9usd CFU/gram in the spleen and usd8.6\times10\sp8usd in the blood of moribund fish. The spleen contained a significantly higher number of cells than any other organ at all sampling time periods. Histological examination of the gills using semi-thin sections showed high numbers of bacteria invading and colonizing the gill lamellae at 24 hours PI. Death of the fish appeared to result from respiratory failure due to necrosis of the gill lamellae and blockage of blood flow to the gills by masses of bacteria in the capillaries. Pathogenic isolates of P. damsela subsp. piscicida were shown to produce an iron siderophore. A wild type strain 91-197, was mutagenized by introduction of a transposon on pEIS, a suicide delivery plasmid by electroporation. A stable mutant (LSU-P1) deficient in siderophore biosynthesis was generated using this system. LSU-P1 evaluated in an immersion infection model for hybrid striped bass and also by IP injection was found to be non-virulent. The insertion of the transposon into the genome of P. damsela subsp. piscicida in LSU-P1 was confirmed by PCR analysis using primers to the kan gene in the transposon.
Subject	:	Aquaculture
	:	Biological sciences
	:	Fish production
	:	Microbiology
	:	Veterinary services
	:	Zoology