International Journal of Basis and Applied Biology Print ISSN: 2394-5820, Online ISSN: 2349-2539, Volume 2, Number 3; October-December, 2014 pp. 152-155 © Krishi Sanskriti Publications http://www.krishisanskriti.org/ijbab.html Antimicrobial Activity of Bioactive Herbal Extracts Against Streptococcus agalactiae Biotype 2 Manoj T. Kamble 1 , Wenresti G. Gallardo 2 , Amararatne Yakupitiyage 3 , Balu R. Chavan 4 , Rachmawati Rusydi 5 and Aulia Rahma 6 1 Ph.D. Scholar, Aquaculture and Aquatic Resource Management (AARM), Food, Agriculture and Biosystem Cluster (FABS), School of Environment, Resources and Development (SERD), Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand 2 Department of Marine Science and Fisheries, College of Agricultural and Marine Sciences Sultan Qaboos University, Oman 3 Aquaculture and Aquatic Resource Management (AARM), Food, Agriculture and Biosystem Cluster (FABS), School of Environment, Resources and Development (SERD), Asian Institute of Technology, P.O. Box 4, Klong Luang, Pathumthani 12120, Thailand 4 Marine Biological Research Station, Ratnagiri, Maharashtra-415629, India 5 Faculty of Marine and Fisheries, Syiah Kuala University, Banda Aceh, Indonesia 6 Research Staff, Dinas Kelautan dan Perikanan Provinsi Aceh, Jl.Tgk. Malem No 7 Kuta Alam, Banda Aceh 23121, Indonesia E-mail: 1 maav.manya@gmail.com, 2 wggallardo@gmail.com, 3 amara@ait.asia, 4 brc15672@gmail.com, 5 r_rusydi_thp43@yahoo.com, 6 r_rusydi_thp43@yahoo.com Abstract: Bacterial infection in aquaculture is mainly controlled by the use of antibiotics. However, indiscriminate use of antibiotics is undesirable, as this often leads to the development of drug resistance and therefore to a reduction in the efficacy of drugs. There is urgent need to look for cheaper and more environmentally friendly alternative approaches to improve the immune system of fish than can act as stimulators to control diseases for sustainable aquaculture. In this study, bioactive extracts from five herbs were extracted using aqueous, chloroform and ethanol as solvents. Antimicrobial activity of aqueous extracts of Aegle marmelos, Emblica officinalis & Moringa oleifera, chloroform and ethanol extracts of Azadirachta indica & Toona sinensis were assessed against S. agalactiae Biotype 2 by using disk diffusion assay. The minimum inhibitory concentrations (MIC) of the herbs were determined by using well diffusion method. Aqueous extract of M. oleifera leaves resulted highest antimicrobial activity with a 13.1 mm inhibition zone and Aegle marmelos leaves extracts resulted lowest antibacterial activity with a 7.9 mm inhibition zone. Chloroform-extracted bioactive substance from Toona sinenses resulted lowest MIC value (0.15 mg/mL) with high efficacy against S. agalactiae Biotype 2. M. oleifera leaves could be a potential source of antimicrobial agents for sustainable aquaculture drug formulation. Keywords: Extracts, Streptococcus agalactiae Biotype 2, Antimicrobial activity, Minimum inhibitory concentration (MIC), Moringa oleifera 1. INTRODUCTION Nile tilapia industry is facing significant losses due to the disease caused by bacterium Streptococcus agalactiae Biotype 2. S. agalactiae is a Gram-positive, non-motile, oxidase- negative, catalase-negative coccus. In unusual circumstances, S. agalactiae is also closely related groups with disease in human, dogs, cows, horses, and guinea pigs (1). Antibiotics are used to treat the diseases but indiscriminate use of antibiotics can have impacts on the environment and consumers. Herbs have been mainly utilized traditionally in human and veterinary medicine. Immunostimulants used in fish culture to control disease, as they offer an alternative to the drugs, chemicals and antibiotics. Nowadays herbs play an important role in aquaculture as good alternatives for disease resistance (2). The use of antibiotics and chemotherapeutics, are the most common strategy for prophylaxis and treatment of Streptococcus. In order to replace antibiotics, the use of natural products will get good alternatives for chemically synthesized antibiotic and growth promoters (3). Immunostimulants have achieved remarkable success as a more environmental friendly approach to fish disease management. Plants generally contain certain bioactive chemical compounds which may be applied in nutrition and as pharmacologically active agents (4). M. oleifera plants are in high demand for their medicinal value in Asia and Africa. Apart from therapeutic (medicinal) benefits, it was reported to be a good source of vitamins & amino acids (5), & also was claimed to boost immune systems (5, 6 & 7).