“Assessing the Suitability of Galleria mellonella Larvae for Vibrio harveyi Virulence Studies (7214)”

Assessing the Suitability of Galleria mellonella Larvae for Vibrio harveyi Virulence Studies

Croatian Veterinary Institute, Zagreb, Croatia

Alfier M, Grbin D, Zrnčić S, Oraić D, Zupičić I G,

Introduction: Understanding host–pathogen interactions is crucial for developing effective strategies to manage infectious diseases in aquaculture. Although vertebrate models such as zebrafish are commonly used, their application is often limited by ethical, financial, and biological constraints. Zebrafish are not useful model for marine fish due to their intolerance to salinities higher than 10ppt. As a result, alternative models are being explored. The larva of the greater wax moth (Galleria mellonella) has emerged as a promising invertebrate host due to its ease of use, low maintenance costs, and an innate immune system that functionally resembles key aspects of fish immunity. This study investigates the suitability of G. mellonella for studying the virulence of Vibrio harveyi, a major bacterial pathogen in marine aquaculture.

Methodology: A Vibrio harveyi strain, isolated from diseased European sea bass from the Adriatic Sea, was used to infect Galleria mellonella larvae. Larvae were injected with 10 μL of bacterial suspension (7 × 10⁶ CFU/mL and 7 × 10⁵ CFU/mL), supernatant, or heat-killed bacteria, and incubated in sealed Petri dishes at 24°C for up to 6 days p/i. Mortality was monitored every 24 h, and survival rates were calculated. Two control groups were included: one group received PBS injections to assess physical trauma, and a second, unmanipulated group was used to evaluate background mortality. Simultaneously, a parallel experiment was conducted on European sea bass (Dicentrarchus labrax) to determine whether similar results would be observed in fish.

Results: In larvae injected with V. harveyi suspension (7 × 10⁶ CFU/mL), 100% mortality was observed 3 days p/i, with the highest mortality occurring within the first 24 h. At the lower dose (7 × 10⁵ CFU/mL), mortality reached up to 26% while larvae injected with bacterial supernatant showed mortality of almost 50% during 6 days p/i, while no mortality was observed in groups receiving heat-killed bacteria or in control groups. Obtained results were in line with those achieved within experimental infection of European seabass fry.

Conclusion: Given increasing restrictions on vertebrate testing, alternative in vivo models are essential. Our findings indicate that Galleria mellonella is a promising alternative host for studying V. harveyi virulence.

1. Alfier, Matea, Croatian Veterinary Institute, Presenter
2. Grbin, Dorotea, Croatian Veterinary Institute, Author
3. Zrnčić, Snježana, Croatian Veterinary Institute, Author
4. Oraić, Dražen, Croatian Veterinary Institute, Author
5. Zupičić, Ivana Giovanna, Croatian Veterinary Institute, Author