Three effective strains of Bacillus amyloliquefaciens (A), Bacillus pumilus (P) and Bacillus subtilis (S) were mixed in pairs at a ratio of 5×10⁸:5×10⁸ CFU/kg diet and coated with the prebiotic chitosan (C) at a concentration of 20 mL/kg diet. The potential synbiotic effects of a Bacillus mixture and chitosan on growth, immune responses and disease resistance against Vibrio parahaemolyticus, the causative agent of acute hepatopancreatic necrosis disease (AHPND) in Pacific white shrimp, were intensively investigated.
The main phenolic compounds related to Vibrio bacteria inhibition were naringin, vanillic acid, and rosmarinic acid, whilst hesperidin, kaempferol pentosyl-rutinoside, and rhamnetin were related to Photobacterium bacteria inhibition. Both extracts affected the swarming and swimming motility and the biofilm formation of the tested bacteria.
macrodontus flower (MIC of 50 mg/mL for all pathogens tested). and 25 mg/mL for Photobacterium spp.) and the methanol extract of S. macrodontus leaf (MIC of 50 mg/mL for Vibrio spp. The highest inhibitory activity against the four pathogens was found with the acetonic extract of S. Besides, the bacterial swimming and swarming motility and biofilm formation were determined. The polyphenol profile of those extracts showing the highest bacterial inhibition were determined. The minimum inhibitory concentration (MIC) of the extracts was determined against Vibrio parahaemolyticus, V. indica extracts were prepared using methanol, acetone, and hexane by ultrasound. Furthermore, the extracts with higher inhibitory activity were analyzed to identify compounds responsible for bacterial inhibition and evaluate their effect on motility and biofilm formation. This study aimed to evaluate the antibacterial activity in vitro of Salpianthus macrodontus and Azadirachta indica extracts against potentially pathogenic bacteria for Pacific white shrimp.
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