Application of predatory bacteria (Bacteriovorax sp.) as a biocontrol agent against the pathogenic Vibrios in Pacific whiteleg shrimp (Penaeus vannamei)

Abstract

Vibriosis, a bacterial disease, is considered a significant threat to the sustainability and economic viability of shrimp production. The present study evaluated the application of a predatory bacterium to control the population growth of pathogenic Vibrios in Pacific whiteleg shrimp (<i>Penaeus vannamei</i>). The predatory bacterium was identified as <i>Bacteriovorax</i> sp. OP175948.1 based on the 16S rRNA sequence. The <i>Vibrio</i>-inhibitory activity of <i>Bacteriovorax</i> sp. was evaluated using two independent trials with <i>P. vannamei</i>, exposed to two pathogenic Vibrios, including <i>Vibrio parahaemolyticus</i> and <i>Vibrio harveyi</i>. Each trial was conducted in five treatments, including a negative control, a positive control, and a treatment with <i>Bacteriovorax</i> sp. applied at 10², 10⁴, and 10⁶ plaque-forming units mL⁻¹ (PFU mL⁻¹). Results indicated that shrimp infected with <i>V. parahaemolyticus</i> and <i>V. harveyi</i>, and then treated with <i>Bacteriovorax</i>, showed a 6-fold increase in survival for <i>V. parahaemolyticus</i> and a 3-fold increase for <i>V. harveyi</i>, relative to the control. The shrimp treated with 10⁴ to 10⁶ <i>Bacteriovorax</i> sp. improved survival associated with a significant decline in <i>Vibrio</i> spp. counts in the shrimp tissues and rearing water. The <i>Bacteriovorax</i> sp. should be used as a practical strategy to prevent <i>Vibrio</i>-associated mortalities in <i>P. vannamei</i> aquaculture.