Quorum quenching potential of Enterococcus faecium QQ12 isolated from gastrointestinal tract of Oreochromis niloticus an
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VETERINARY MICROBIOLOGY - RESEARCH PAPER
Quorum quenching potential of Enterococcus faecium QQ12 isolated from gastrointestinal tract of Oreochromis niloticus and its application as a probiotic for the control of Aeromonas hydrophila infection in goldfish Carassius auratus (Linnaeus 1758) Divya Haridas Vadassery 1,2
&
Devika Pillai 1
Received: 26 September 2019 / Accepted: 13 January 2020 # Sociedade Brasileira de Microbiologia 2020
Abstract Quorum quenching (QQ), the obstruction of quorum sensing, is the most attractive way to break down the N-acyl-homoserine lactones (AHL) molecules. This work was focused at isolating AHL degrading bacteria from gastrointestinal tract of Oreochromis niloticus, with abilities appropriate for use as probiotic in aquaculture. The presence of an autoinducer inactivation (aiiA) homolog gene and AHL inactivation assay showed that Enterococcus faecium QQ12, which was one among the 20 isolates, could rapidly degrade synthetic C6-HSL in vitro and hampered violacein production by Chromobacterium violaceum. It had excellent biodegrading ability of natural N-AHL produced by Aeromonas hydrophila, suggesting that it can be used as a potential quencher bacterium for disrupting the virulence of A. hydrophila. It was susceptible to all the five antibiotics tried out. The isolate grew well at pH 3.0ā7.0, was resistant to high level of bile salts (0ā0.9%) and 0.5% of phenol. QQ12 also exhibited high degree of auto-aggregation and co-aggregation, confirming that it possessed good probiotic attributes. Goldfish fed diet incorporated with 108 and 1010 CFU gā1 of the QQ12 for 30 days showed 76.66ā86.66% survival when challenged with A. hydrophila. The study indicates that Enterococcus faecium QQ12 could be used as a non-antibiotic feed additive in aquaculture to control bacterial diseases. Keywords Enterococcus faecium . N-acyl-homoserine lactones . Probiotic . Quorum sensing . Quorum quenching
Introduction Aeromonas hydrophila, a Gram-negative, motile rod is regarded as one of the most important aquaculture pathogen causing motile aeromonas septicemia or ulcer disease in fish [1, 2]. This disease affects large number of tropical or ornamental fish. The unlimited use of antibiotics for the control of bacterial infection in aquaculture can lead to the development of antibiotic resistance in pathogenic bacteria. Alternative
Responsible Editor: Waldir P. Elias. * Divya Haridas Vadassery [email protected] 1
Department of Aquatic Animal Health Management, Kerala University of Fisheries and Ocean Studies, Kochi, Kerala, India
2
School of Biosciences, Mahatma Gandhi University, Kottayam, Kerala, India
biocontrol strategies are therefore needed for sustainable development of the aquaculture industry. One such approach that is as equally functional as antibiotics is to impede the bacterial signaling pathways controlling the production of virulence factors. Quorum sensing (QS) is a mechanism by which majority of microorganisms communicate with each other and make response collectively to a dynamic
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