BURGENTS, J.E.*; BURNETT, K.G.; STABB, E.V.; BURNETT, L.E.; College of Charleston; College of Charleston; Univ. of Georgia; College of Charleston: The Clearance and Tissue Distribution of a Live, Pathogenic Vibrio sp. in the Pacific White Shrimp, Litopeneaus vannamei
Although numerous mechanisms of immune defense have been described in crustaceans, including anti-microbial peptides, the prophenoloxidase cascade, and respiratory burst, the coordination of these mechanisms in response to pathogen challenge remains unclear. Several published reports suggest that injected bacteria are cleared rapidly from the hemolymph with the gill serving as the major site of subsequent accumulation. Few, if any, of these studies have focused on quantifying the tissue distribution and fate of live injected bacteria within the host. In the current study Litopenaeus vannamei were injected in the third abdominal segment with 2×104/g body weight of a pathogenic strain of Vibrio sp. that expresses green fluorescent protein (GFP) and resistance to kanamycin (gfp-kanR-VC). Culturable gfp-kanR-VC were quantified in the hemolymph, gills, heart, lymphoid organ, hepatopancreas, and injection site at 15, 60, and 240 minutes post injection (p.i.). At 15 minutes p.i. the injection site contained the greatest amount of recoverable bacteria (75%). In the hemolymph, the percent of recoverable live bacteria decreased from approximately 15% at 15 minutes p.i. to 2% at 60 minutes. Of the remaining tissues, the majority of live bacteria were recovered from the gill and hepatopancreas (3% each at 15 min p.i.). Low amounts of live bacteria were recovered at 15 minutes from the lymphoid organ (0.5%), which has been suggested by others as a possible site of accumulation. The amount of bacteria recovered from the injection site did not decrease over 240 minutes suggesting an absence of killing at this site. In each of the remaining tissues total culturable bacteria decreased over time, becoming undetectable by 240 minutes p.i. (NSF IBN-0212921.)
