Biology subjects

St-Hilaire, S.

Publications and source records attributed to St-Hilaire, S..

3 recordsLinked to original sources

bioRxiv2023

Innovative approach for vaccinating Nile tilapia, Oreochromis niloticus against Streptococcus agalactiae using an ozone nanobubble pre-treatment, VAC in BAG and VAC in FEED

The treatment of Nile tilapia with ozone nanobubbles (ONb) prior to vaccination with an immersible heat-killed Streptococcus agalactiae (Sa) vaccine has been reported to modulate and enhance both innate and specific immunity. The efficacy of this novel vaccination strategy is explored further in field trials. This strategy involved a short-term treatment of ONb to activate the fishs immunity prior to immersion vaccination during their transportation in oxygenated plastic bags (VAC in BAG), followed by two oral boosters during the grow-out stage mixing vaccine in feed (VAC in FEED). The field trial was conducted over 112 days in open cages, comprising four groups: normal aeration control (AC), normal aeration + vaccine (AV), ONb control (NC), and ONb + vaccine (NV). The efficacy of the vaccine was evaluated by measuring specific antibodies for S. agalactiae, monitoring expressions of IgM and IgT transcripts in the gills and head kidney every two weeks, and a laboratory pathogen challenge. Results found that fish in the NV group had significant increases in anti-S. agalactiae antibodies after the primary dose, whereas fish in the AV group required an oral booster dose to produce significant anti-S. agalactiae antibodies. In the vaccinated groups (AV and NV), only IgM was observed to be upregulated at 14 days post-immersion (dpi), while this gene was upregulated in both gills and head kidney in the NC group. No statistically significant upregulation of IgT was recorded in any group at any time point. Despite a decline in the levels of specific antibodies among the vaccinated groups at the time of challenge (88 dpi), the NV and AV groups demonstrated a relative percent survival (RPS) of 50% and 46.7%, respectively, following a relatively high injection dose of S. agalactiae injection (0.1 mL of 108 CFU/mL). In summary, this ONb, VAC in BAG and VAC in FEED vaccination strategy represents a promising alternative to the undesirable handling and costly injection approach used within the Nile tilapia industry.

immunology↗

bioRxiv2021

Air-nanobubbles ineffective to reduce pathogenic bacteria in fresh and brackish waters

Nanobubble (NB) technology has been hailed as a novel way to disinfect water. Previous studies suggested that when NBs collapse, they create shock waves that result in OH- free radicals, which can damage cells, including bacteria. In this study, we investigated, through a series of 11 experiments, the potential use of air nanobubbles (128 {+/-} 44 nm, mean {+/-} SD) to reduce the concentration of various pathogenic bacteria including Aeromonas hydrophila, A. veronii, Vibrio parahaemolyticus, and Streptococcus agalactiae under controlled, tank-based laboratory conditions. Despite the high number of nanobubbles continuously added to a relatively small volume of water in experimental tanks (50-100 L), we did not observe a consistent or significant decrease in bacteria that would control disease outbreaks. Although most of the experiments were conducted in fresh water on A. hydrophila, results were consistent across fresh and brackish water experiments, Gram-negative and Gram-positive bacteria, and a range of nanobubble concentrations. This study suggests air nanobubbles on their own are inadequate to significantly reduce high levels of pathogenic bacteria in water. We propose to explore other gases for improving the disinfection properties of this technology. SIGNIFICANCE STATEMENTAir nanobubbles did not sufficiently reduce the level of bacteria in laboratory experiments.

microbiology↗

bioRxiv2020

Ozone nanobubble treatment effectively reduced pathogenic Gram positive and negative bacteria in freshwater and safe for tilapia

High concentrations of pathogenic bacteria in water usually results in outbreaks of bacterial diseases in farmed fish. Here, we explored the potential application of an emerging nanobubble technology in freshwater aquaculture. Specifically, we aimed to determine if this technology was effective at reducing the concentration of pathogenic bacteria in the water, and to assess whether it was safe for fish. An ozone nanobubble (NB-O3) treatment protocol was established based on examination of nanobubble size, concentration, disinfection property, and impact on fish health. A 10-min treatment with NB-O3 in 50 L water generated approximately 2-3 x 107 bubbles with majority sizes less than 130 nm and ozone level of [~]800 mV ORP. A single treatment with water contaminated with either Streptococcus agalactiae or Aeromonas veronii effectively reduced 96.11-97.92 % of the bacterial load. This same protocol was repeated 3 times with 99.93-99.99 % reduction in the bacterial concentration. In comparison, bacterial concentration the control tanks remained the same level during the experiments. In fish-cultured water with the presence of organic matter (e.g. mucus, feces, bacterial flora, feed, etc.), the disinfection property of NB-O3 was reduced i.e bacterial concentration was reduced by 42.94 %, 84.94 % and 99.27 % after the first, second and third treatments, respectively. To evaluate the safety of NB-O3 to fish, juvenile Nile tilapia were exposed to NB-O3 treatment for 10 minutes. No mortality was observed during the treatment or 48 h post treatment. Gill histology examination revealed that a single NB-O3 treatment caused no alteration morphology. However, damage in the gill filaments was noticed in the fish receiving two or three consecutive exposures within the same day. Results of all the experiments conducted in this study suggest that NB-O3 technology is promising for controlling pathogenic bacteria in aquaculture systems, and may be useful at reducing the risk of bacterial disease outbreaks in farmed fish.

microbiology↗