Synergistic Antimicrobial Effect of a Seaweed-Probiotic Blend Against Acute Hepatopancreatic Necrosis Disease (AHPND)-Ca
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Synergistic Antimicrobial Effect of a Seaweed-Probiotic Blend Against Acute Hepatopancreatic Necrosis Disease (AHPND)-Causing Vibrio parahaemolyticus Shen-Yin Lim 1 & Keat Wei Loo 1 & Wey-Lim Wong 1
# Springer Science+Business Media, LLC, part of Springer Nature 2019
Abstract The outbreak of acute hepatopancreatic necrosis disease (AHPND) has caused great economic losses to the shrimp culture sector. However, the use of antibiotics to fight this disease has resulted in negative impacts on human health and the environment. Thus, the use of natural alternatives to antibiotics may be a better solution. In this study, four Bacillus species obtained from the guts of shrimps (Fenneropenaeus penicillatus and Penaeus monodon) showed antimicrobial activity against the AHPND-causing Vibrio parahaemolyticus strain 3HP using the cross-streaking and agar spot methods. Two of the Bacillus isolates, B2 and BT, also showed good probiotic properties, exhibiting tolerance to bile, good adhesion to shrimp mucus, non-hemolytic, susceptibility to antibiotics and being safe towards hosts. Moreover, a seaweed-probiotic blend (a combination of Bacillus B2 and 20 mg/ml of the red seaweed Gracilaria sp.) exhibited synergistic in vitro inhibition against V. parahaemolyticus strain 3HP, with an observed inhibition zone of 5.0 mm. The broth co-culture experiment results further indicated that the seaweed-probiotic blend inhibited V. parahaemolyticus through competitive exclusion. The in vivo challenge trials also confirmed that this seaweed-probiotic blend significantly reduced the mortality of shrimps post-challenge with the AHPND-causing V. parahaemolyticus strain 3HP (p < 0.05) compared to the negative control (mortality rate = 13.88% vs 72.19%). Thus, this seaweed-probiotic blend may serve as an alternative to antibiotics in controlling the outbreak of AHPND. Keywords Antimicrobial . Early mortality syndrome . Probiotic . Seaweed . Shrimp . Synergistic
Introduction Whiteleg shrimp (Litopenaeus vannamei) is one of the most popular cultured shrimp species worldwide [1]. However, outbreaks of acute hepatopancreatic necrosis disease (AHPND) have caused significant economic losses in L. vannamei shrimp culture since 2009 [2]. AHPND was first determined to be caused by a specific strain of Vibrio parahaemolyticus in 2013 [2]. Subsequently, Lee et al. [3] demonstrated that AHPNDcausing V. parahaemolyticus carries an extrachromosomal plasmid, pVA1 (~ 70 kbp), which encodes the deadly binary toxins PirAvp/PirBvp that destroy the hepatopancreatic tissues of shrimps and causes high mortality rates [3, 4]. Later, AHPND was also demonstrated to be caused by other species of Vibrio, such as * Wey-Lim Wong [email protected] 1
Department of Biological Science, Faculty of Science, Universiti Tunku Abdul Rahman, Jalan Universiti, Bandar Barat, 31900 Kampar, Perak, Malaysia
V. campbellii [5], V. punensis [6] and V. owensii [7]. All of these species were shown to carry toxins that are highly similar to PirAvp/PirBvp. The PirAvp/PirBvp-encoding genes can
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