Biocontrol of Vibrio harveyi in Penaeus monodon larvae rearing: 1. isolation of inhibiting bacteria

anglais. Vibrio harveyi infection is one of the serious problems in larval rearing of Penaeus monodon causing mass mortality of larvae. Control of this disease is usually done by using chemicals or antibiotics but not so effective. The use of non pathogenic bacteria living in the coastal aquaculture environment to inhibit the development of luminescent bacteria V. harveyi could be an effective and safe method in preventing the outbreak of luminescent disease in shrimp culture. This experiment was performed in Gondol Research Station for Coastal Fisheries, Bali from November 1994 to February 1995. A hundred and twenty five isolates of bacteria were isolated from sea water, pond water, rearing water of larvae and adult shrimps. Isolates of V. harveyi were obtained from larvae rearing water of P. monodon at private hatcheries. A series of inhibitory tests of 125 isolates on the growth of V. harveyi on MA medium were carried out. Result of these tests indicated that isolates GSB-95030, GSB-95033, and GSB-95040 were effective in inhibiting the growth of V. harveyi. Pathogenicity test of the isolates on larvae zoea-1 stage, indicated these isolates did not cause mortality of the larvae at a density of 10 at the power of 8 cfu/mL. The application of these non pathogenic isolates into larval rearing tanks proved to be effective in supressing the population of pathogenic V. harveyi until the level of less than 8.35 x 10 at the power of 4 cfu/mL, resulting high survival rate of shrimp larvae

indonésien. Vibrio harveyi merupakan ancaman serius pada usaha perbenihan udang windu (Penaeus monodon) yang menyebabkan kematian massal larva. Cara umum untuk pengendalian penyakit ini biasanya dengan penggunaan bahan kimia maupun antibiotik tetapi kurang efektif karena tingkat keberhasilannya masih sangat rendah. Penggunaan jenis bakteri nonpatogen yang hidup pada lingkungan budidaya pantai dan dapat menekan perkembangan V. harveyi penyebab penyakit kunang-kunang pada budidaya udang windu (P. monodon) mungkin merupakan salah satu cara penanggulangan secara biologis yang aman. Penelitian dilakukan di Loka Penelitian Perikanan Pantai Gondol, Bali dari November 1994 sampai Februari 1995. Dari hasil pengambilan contoh dari berbagai sumber, di antaranya dari air laut, air pemeliharaan larva udang windu, dan udang telah diisolasi 125 isolat bakteri penghambat. Isolat bakteri bercahaya V. harveyi diisolasi dari air pemeliharaan larva udang windu di panti benih komersial. Terhadap semua isolat bakteri dilakukan uji daya hambat dalam menekan perkembangbiakan V. harveyi pada media Marine Agar (MA). Tiga isolat (GSB-95030, GSB-95033 dan GSB-95040) mampu menghambat perkembangbiakan V. harveyi, dan dari tingkat patogenisitasnya terhadap larva udang windu ternyata sampai kepadatan 10 pangkat 8 cfu/mL tidak mematikan larva udang windu stadia zoea-1. Isolat bakteri tersebut digunakan sebagai kontrol biologi dalam air pemeliharaan larva dan mampu menekan pertumbuhan bakteri V. harveyi sehingga berada pada kondisi aman (lebih kecil dari 8,35 x 10 pangkat 4 cfu/mL) dan memberikan sintasan larva udang yang lebih tinggi dibanding kontrol