Vibrios associated with Litopenaeus vannamei larvae, postlarvae, broodstock, and hatchery probionts

Abstract

Several bacteriological surveys were performed from 1994 to 1996 at different Litopenaeus vannamei hatcheries (in Ecuador) and shrimp farms (in Mexico). Samples were taken from routine productions of healthy and diseased L. vannamei larvae, postlarvae, and their culture environment and from healthy and diseased juveniles and broodstock. In Ecuador, the dominant bacterial flora associated with shrimp larvae showing symptoms of zoea 2 syndrome, mysis mold syndrome, and bolitas syndrome has been determined. Strains were characterized by Biolog metabolic fingerprinting and identified by comparison to a database of 850 Vibrio type and reference strains. A selection of strains was further genotypically fine typed by AFLP. Vibrio alginolyticus is predominantly present in all larval stages and is associated with healthy nauplius and zoea stages. AFLP genetic fingerprinting shows high genetic heterogeneity among V. alginolyticus strains, and the results suggest that putative probiotic and pathogenic strains each have specific genotypes. V. alginolyticus was found to be associated with larvae with the zoea 2 syndrome and the mysis mold syndrome, while different Vibrio species (V. alginolyticus and V. harveyi) are associated with the bolitas syndrome. V. harveyi is associated with diseased postlarvae, juveniles, and broodstock. The identities of the strains identified as V. harveyi by the Biolog system could not be unambiguously confirmed by AFLP genomic fingerprinting. Vibrio strain STD3-988 and one unidentified strain (STD3-959) are suspected pathogens of only juvenile and adult stages. V. parahaemolyticus, Photobacterium damselae, and V. mimicus are associated with juvenile and adult stages.

FIG. 1

Distribution of bacteria isolated from healthy and diseased L. vannamei larvae, juveniles, and broodstock and their environment at different hatcheries in Ecuador and Mexico. H, isolates from healthy L. vannamei; D, isolates from diseased L. vannamei (isolates from shrimp with bolitas negricans, mysis mold syndrome, and zoea 2 syndrome are not included); environment H and D, isolates from inlet water, wastewater, tank water, nearshore seawater, and food of healthy and diseased larvae, respectively.

FIG. 2

AFLP fingerprints of whole genomes of representative V. alginolyticus and V. harveyi strains (previously identified by Biolog) isolated from diseased and healthy L. vannamei larvae, postlarvae, juveniles, and hatchery probionts and from Vibrio reference strains. The Pearson product moment correlation coefficient was used for comparison of the AFLP fingerprints. The isolates were grouped by UPGMA using the software package GelCompar 4.0.