LPS-Induced Mortality in Zebrafish: Preliminary Characterisation of Common Fish Pathogens

Area of Science:

• Aquatic animal health
• Bacteriology
• Immunology

Background:

• Aquaculture faces significant economic losses due to bacterial disease outbreaks.
• Gram-negative bacteria, such as Vibrio spp. and Aeromonas spp., are major pathogens in aquaculture.
• Lipopolysaccharides (LPS) from Gram-negative bacteria are known for their strong immunogenic properties in vertebrates.

Purpose of the Study:

• To investigate the effects of lipopolysaccharides (LPS) from common fish pathogens on zebrafish (Danio rerio) larvae.
• To determine the differential mortality rates induced by LPS from various bacterial species.

Main Methods:

• Lipopolysaccharides (LPS) were extracted from Aeromonas hydrophila, Vibrio harveyi, Tenacibaculum maritimum, and Photobacterium damselae using a hot-phenol procedure.
• Purified LPS were administered to 3 days post-fertilisation (dpf) zebrafish larvae at concentrations of 50, 100, 250, and 500 µg mL⁻¹ for 5 days.
• Mortality rates were recorded, and LPS structures were analyzed using gel electrophoresis.

Main Results:

• Photobacterium damselae LPS did not induce mortality in zebrafish larvae at any tested concentration.
• Aeromonas hydrophila LPS caused 15.5% mortality, and Vibrio harveyi LPS caused 58.3% mortality at 500 µg mL⁻¹.
• Tenacibaculum maritimum LPS was the most lethal, resulting in 80.6% mortality at 500 µg mL⁻¹.
• Gel electrophoresis revealed structural variations in LPS among the tested bacterial species.

Conclusions:

• Lipopolysaccharides from different fish pathogenic bacteria exhibit varying levels of toxicity to zebrafish larvae.
• Structural differences in LPS may explain the observed variations in induced mortality.
• This study provides insights into the role of LPS in fish disease pathogenesis and potential targets for disease control in aquaculture.