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p. makridis, s. martins, t. vercauteren, k. van driessche, o. decamp and m.t. dinis. 2005.The aim of this study was to evaluate the effect of six bacterial strains on gilthead sea bream larvae (Sparus aurata).Six bacterial strains isolated from well-performing live food cultures were identified by sequencing fragments of their 16s rDNA genome to the genus level asCytophagasp.,Roseobactersp.,Ruergeriasp.,Paracoccussp.,Aeromonassp. andShewanellasp. Survival rates of gilthead sea bream larvae transferred to seawater added these bacterial strains at concentrations of 6 ± 0·3 × 105 bacteria ml−1 were similar to those of larvae transferred to sterilized seawater and showed an average of 86% at 9 days after hatching, whereas, survival rates of larvae transferred to filtered seawater were lower (P < 0·05), and showed an average of 39%, 9 days after hatching.Several bacterial strains isolated from well-performing live food cultures showed a positive effect for sea bream larvae when compared with filtered seawater.The approach used in this study could be applied as anin vivoevaluation method of candidate probiotic strains used in the rearing of marine fish larvae. [ABSTRACT FROM AUTHOR]

Tilapia lake virus (TiLV) causes an emerging viral disease associated with high mortality and economic damage in tilapia farming around the world. The use of probiotics in aquaculture has been suggested as an alternative to antibiotics and drugs to reduce the negative impact of bacterial and viral infections. In this study, we investigate the effect of probiotic Bacillus spp. supplementation on mortality, viral load, and expression of immune-related genes in red hybrid tilapia ( Oreochromis spp.) upon TiLV infection. Fish were divided into three groups, and fed with: control diet, 0.5% probiotics-supplemented diet, and 1% probiotics-supplemented diet. After 21 days of experimental feeding, the three groups were infected with TiLV and monitored for mortality and growth performances, while organs were sampled at different time points to measure viral load and the transcription modulation of immune response markers. No significant difference was found among the groups in terms of weight gain (WG), average daily gain (ADG), feed efficiency (FE), or feed conversion ratio (FCR). A lower cumulative mortality was retrieved from fish fed 0.5% and 1% probiotics (25% and 24%, respectively), compared to the control group (32%). Moreover, fish fed with 1% probiotic diet had a significantly lower viral load, than those fed with 0.5% probiotic and control diet at 5, 6, 9, and 12 days post infection-challenge (dpc). The expression patterns of immune-related genes, including il-8 (also known as CXCL8), ifn-γ , irf-3 , mx , rsad-2 (also known as VIPERIN) showed significant upregulation upon probiotic treatment during the peak of TiLV pathogenesis (between 9 and 12 dpc) and during most of the study period in fish fed with 1% probiotics-supplemented diet. Taken together, these findings indicate that dietary supplementation using Bacillus spp. probiotics may have beneficial effects to strengthen tilapia immunity and resistance against TiLV infections. Therefore, probiotic treatments may be preventively administered to reduce losses caused by this emerging viral infection in tilapia aquaculture.

Changes in the viability of Vibrio cholerae 0139 Bengal, estimated by cellular membrane integrity, in batch culture over 35 days, were investigated. Data indicated an initial period of rapid growth with up to 30% of bacterial mortality, followed by a period of slower growth, lower culturability but higher viability, from day 7 onwards. The size of viable bacteria significantly decreased during the incubation time, whilst the size of dead bacteria showed a less pronounced decrease. V. cholerae 0139 changed from a straight or curved rod shape to a spherical shape. This study shows that BacLight dyes are a fast and useful tool to examine health risk-associated bacteria, providing useful information about their viability and concentration.