Phloroglucinol shows prophylactic and metaphylactic effects against pathogenic stressors in Macrobrachium larvae.

Vibriosis caused by Vibrio campbellii and related species is amongst the major hindrance to the sustainable expansion of giant freshwater prawn Macrobrachium rosenbergii larviculture. Induction of heat shock protein Hsp70 is a natural response of stressed organisms that protect against many insults including vibriosis in aquaculture animals. Therefore, there is a great interest in searching for natural compounds that could induce Hsp70 in animals in a non-invasive manner. Previously, in a series of in vivo studies, we have shown that the phenolic compound phloroglucinol could induce Hsp70 in aquaculture organisms Macrobrachium and Artemia. This led to a significant increase in the resistance of the animals towards subsequent challenges with V. parahemolyticus. As V. parahaemolyticus belongs to the Harveyi clade similar to V. campbellii, our above findings triggered the hypothesis that phloroglucinol is a potential anti-microbial agent that could protect the freshwater prawn against V. campbellii infection. The results presented here provide evidence that the Hsp70-inducing compound phloroglucinol could induce both metaphylactic and prophylactic effects against infection stress mediated by V. campbellii. The wide-spectrum property of the compound to both prevent the occurrence and reduce the spread of V. campbellii infection in prawn larvae without affecting the larval growth makes it a potential natural agent for health management and V. campbellii-mediated disease control in freshwater prawn larvae. Overall results add new information about the functional properties of phloroglucinol and advance our knowledge of this compound as a potential antimicrobial agent for the sustainable production of giant freshwater prawns.