Pinanong Na-Phatthalung1, Sasitorn Chusri2, Naraid Suanyuk3, Supayang Piyawan Voravuthikunchai1. 1. Department of Microbiology and Excellence Research Laboratory on Natural Products, Faculty of Science and Natural Product Research Center of Excellence, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. 2. Faculty of Traditional Thai Medicine, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand. 3. Department of Aquatic Science, Faculty of Natural Resources, Prince of Songkla University, Hat Yai, Songkhla 90112, Thailand.
Abstract
PURPOSE: Rhodomyrtustomentosa is a Thai medicinal plant that has been attracting attention for its remarkable antibacterial properties against Gram-positive pathogenic bacteria. The purpose of this study was to evaluate the antibacterial properties of R. tomentosa leaf extract against Streptococcus agalactiae and Streptococcus iniae isolated from infected tilapia. METHODOLOGY: The anti-streptococcal activity of R. tomentosa was determined using broth microdilution assays. RESULTS: The extract demonstrated strong antibacterial activity against the fish pathogens, with minimum inhibitory concentrations (MICs) ranging from 7.8‒62.5 µg ml-1. It was found to possess a dose-dependent bacteriostatic effect on this organism. Scanning electron microscopy revealed irregular and long chains of swollen cells, as well as corkscrew shapes andincomplete separation of cell division of S. agalactiae cells following the treatment at sub-MIC. Moreover, S. agalactiae cells pre-treated with the extract became more sensitive to oxidative stress induced by H2O2 than the untreated cells. Based on the mortality of Nile tilapia after intraperitoneal infection of S. agalactiae at median lethal dose (LD50), the pre-treated cells caused a significant (P<0.01) reduction in mortality of S. agalactiae-infected Nile tilapia. CONCLUSION: The results suggested that R. tomentosa could be further developed as a simple and effective agent for the treatment of streptococcosis in Nile tilapia.
PURPOSE:Rhodomyrtustomentosa is a Thai medicinal plant that has been attracting attention for its remarkable antibacterial properties against Gram-positive pathogenic bacteria. The purpose of this study was to evaluate the antibacterial properties of R. tomentosa leaf extract against Streptococcus agalactiae and Streptococcus iniae isolated from infected tilapia. METHODOLOGY: The anti-streptococcal activity of R. tomentosa was determined using broth microdilution assays. RESULTS: The extract demonstrated strong antibacterial activity against the fish pathogens, with minimum inhibitory concentrations (MICs) ranging from 7.8‒62.5 µg ml-1. It was found to possess a dose-dependent bacteriostatic effect on this organism. Scanning electron microscopy revealed irregular and long chains of swollen cells, as well as corkscrew shapes andincomplete separation of cell division of S. agalactiae cells following the treatment at sub-MIC. Moreover, S. agalactiae cells pre-treated with the extract became more sensitive to oxidative stress induced by H2O2 than the untreated cells. Based on the mortality of Nile tilapia after intraperitoneal infection of S. agalactiae at median lethal dose (LD50), the pre-treated cells caused a significant (P<0.01) reduction in mortality of S. agalactiae-infected Nile tilapia. CONCLUSION: The results suggested that R. tomentosa could be further developed as a simple and effective agent for the treatment of streptococcosis in Nile tilapia.
Authors: François Chassagne; Tharanga Samarakoon; Gina Porras; James T Lyles; Micah Dettweiler; Lewis Marquez; Akram M Salam; Sarah Shabih; Darya Raschid Farrokhi; Cassandra L Quave Journal: Front Pharmacol Date: 2021-01-08 Impact factor: 5.810