Vibrio Community Research Articles

Influence of Timsen™ on Vibrio populations of culture pond water and hepatopancreas and on the hemocytic activity of tiger shrimp (Penaeus monodon)

The addition of Timsen™ (alkyl dimethyl benzyl ammonium chloride-40-active) to a shrimp culture pond effectively prevented the occurrence of vibriosis in shrimp. The results indicated that Timsen™ could effectively reduce the number of total heterotrophic bacteria in water samples, but its efficacy was reduced in brackish as compared with fresh water. A significant reduction of the number of Vibrio species in brackish water samples was also observed. In the hepatopancreas of shrimp collected from a control pond, a rapid increase in the number of Vibrio was observed with the onset of disease. With prolonged exposure (120 h), Timsen™ still maintained lower Vibrio numbers in brackish water samples, with no difference in total numbers of heterotrophic bacteria between control samples and treated brackish water samples. Further analysis of the composition of the Vibrio species suggested that Timsen™ also caused a change in the components of the Vibrio community. Results also indicated that Timsen™ may affect the hemocytic activity of shrimp by enhancing the activity of phagocytosis and/or encapsulation; however, it also induces hemocyte death via apoptosis.

Relationships between disease outbreak in cultured tiger shrimp ( Penaeus monodon) and the composition of Vibrio communities in pond water and shrimp hepatopancreas during cultivation

Tiger shrimp ( Penaeus monodon) larvae were first cultivated for 1 month in the same pond and then at postlarval 43 were transferred into three different culture ponds (E2, E4, and W4). Vibrio spp. from the pond water and shrimp hepatopancreas were isolated and identified using thiosulfate-citrate-bile salt-sucrose (TCBS) agar and fatty acid methyl esters (FAME) analysis. For the initial 60 days after transfer, the composition of the Vibrio community in the pond water remained fairly diverse, but subsequently decreases in species diversity were observed in all three ponds, suggesting that the culture system was under some kind of stress. However, no clear relationship between this reduction in species diversity, and the subsequent occurrence of disease to the changes in total viable and Vibrio counts were observed. Although the Vibrio community in pond E4 remained relatively diverse, in water samples taken from E2 and W4 between Day 73 and 89, the dominant species according to FAME were Vibrio cholerae and, apparently, Vibrio furnissii/ Aeromonas spp., respectively. By Day 95, at which time all the shrimps, including those in pond E4, were dead, the microbial communities in all these ponds appeared to be dominated by Aeromonas spp. and V. furnissii. When thirty-eight of these Aeromonas spp. and V. furnissii isolates were randomly selected and re-identified using Biolog GN plates, the majority of them (58%) were reassigned either to Vibrio parahaemolyticus or the Vibrio harveyi/ Vibrio carchariae group. Vibrios were only detected once in the hepatopancreas of shrimp from pond E2. In W4 shrimp, more than 10 4 CFU of vibrios/g were detected in samples taken on Day 62 and thereafter. The average weight of shrimp collected on Day 89 from ponds W4 and E2 was 4.91 and 7.96 g, respectively, which suggests that the presence of a large number of vibrios in the hepatopancreas may be associated with growth retardation in shrimps. The Biolog system identified 53.3% of the vibrios isolated from the hepatopancreas of shrimps collected from pond W4 on Day 62, as V. harveyi and 20% as V. parahaemolyticus. One month later, immediately before mass mortality of the shrimp, Biolog results suggested that the W4 hepatopancreatic Vibrio communities were dominated by V. parahaemolyticus.

Changes in the composition of Vibrio communities in pond water during tiger shrimp ( Penaeus monodon) cultivation and in the hepatopancreas of healthy and diseased shrimp

Two batches of shrimp were cultivated in a total of 4 culture ponds from March 28 to June 13, and July 17 to September 11, 1997. Vibrio spp. were isolated from the pond water and the hepatopancreas of healthy and diseased shrimp using thiosulfate–citrate–bile salt–sucrose agar plate, and then identified using fatty acid methyl ester (FAME) analysis. In each culture pond, decreases in the diversity of the Vibrio community were observed prior to outbreaks of vibriosis. FAME analysis suggested that in diseased pond water (i.e., water from a pond in which there had been an outbreak of disease) and the hepatopancreas of diseased shrimp, V. furnissii was the major component of the Vibrio community. However, since identification confidence levels were too low (≤0.500), the identity of 48 randomly selected putative V. furnissii was further checked using the Biolog system. Of these, 27 were identified as V. harveyi/V. carchariae, six as V. parahaemolyticus, five as V. anguillarum, four as V. alginolyticus, four as V. vulnificus, and two as V. damsela, the majority of which species are known to be associated with diseased shrimp. Similar results were also found for Vibrio communities in the hepatopancreas of diseased shrimps, with 68.2% of the isolated vibrios eventually identified as V. harveyi/ V. carchariae.