NATURAL COMPONENTS TO COMBAT DISEASES.  PARTIM 2: synergistic mix OF ANTIMICROBIAL COMPOUNDS REDUCES VIBRIO PATHOGENS IN SHRIMP

Patrick Lavens*, Eva Bequé, Mathias Corteel, Mathieu Wille, Margriet Drouillon, Peter Bossier, Geert Rombaut
 
INVE Technologies, Hoogveld 93, 9200 Dendermonde (Belgium)
e-mail: p.lavens@inveaquaculture.com

Loss of production due to bacterial and viral infections has been a recurring problem in aquaculture for decades now. The fact that mortality is often perceived as uncontrollable, is mainly due to a lack of a holistic approach in developing control strategies. Often, broad-spectrum disinfectants or antibiotics are employed, which temporarily suppress pathogens. However, the root cause why opportunistic r-strategic bacteria can rise to power in aquaculture systems in the first place, is a suboptimal and immature microbial flora. Hence, we advocate for the application of targeted, selective, and natural antimicrobials that specifically inhibit pathogenic bacteria, and immediately re-colonize their empty niche with probiotic bacteria.

In a joint IWT research project between IAQ and Ghent University, a variety of compounds from plant origin were tested, which show a selective bactericidal action against pathogenic Vibrio. A gnotobiotic Artemia model was used for the proof of concept of microbial management strategies, including quorum sensing interference (QSi). Treatments with the compounds resulted in a doses-related bactericidal or bacteriostatic effect against pathogenic isolates of V. harveyi, V. campbellii, V. anguillarum and V. parahaemolyticus. However, and unexpected, the underlying mechanism was not QSi but inhibition. In bacterial challenges of Artemia, therapeutic application of the compounds significantly increased the survival from 30±5% to 60±7% (Fig.1). Based on this, a mix of natural components was developed to reduce the Vibrio load of P. vannamei post larvae during transport, thereby limiting the risk of transferring pathogens to the ponds or nursery tanks.

In conclusion, through extensive scientific research and development, different applications for selective antibacterials based on synergistic mixes of natural components were formulated. These components successfully manage the microbial community by selectively suppressing pathogenic bacteria whilst not disturbing the established microbial flora and thereby leaving the system less vulnerable to recolonizations of new pathogenic bacteria.