TOKSISITAS SEL UTUH DAN EXTRACELLULAR PRODUCT (ECP) Streptococcus agalactiae β-HEMOLITIK DAN NON-HEMOLITIK PADA IKAN NILA (Oreochromis niloticus)
Authors: Suhermanto Achmad , Sukenda Sukenda , Zairin Jr. Muhammad , Lusiastuti Angela Mariana , Nuryati Sri 
Published: May 2019

Bakteri Streptococcus agalactiae tipe β-hemolitik dan non-hemolitik menjadi agen penyebab infeksi streptococcosis yang mengakibatkan kematian dan kerugian besar pada budidaya ikan nila. Penelitian ini bertujuan untuk membandingkan toksisitas sel utuh dan extracellular product (ECP) bakteri b-hemolitik dan non-hemolitik yang diinjeksikan pada ikan nila. Karakterisasi S. agalactiae berdasarkan SNI dan API 20 STREP, serta pemisahan protein dengan metode SDS-PAGE. Pengujian toksisitas dilakukan dengan cara menginjeksikan sel utuh dan ECP S. agalactiae secara intraperitoneal (IP) dengan dosis 0,1 mL ekor-1. Hasil uji biokimia, dan konfirmasi dengan API 20 STREP menunjukkan bahwa semua isolat positif S. agalactiae. Fraksinasi protein pada sel utuh bakteri diperoleh pita protein masing-masing sebanyak sembilan dan tujuh pita pada tipe β-hemolitik dan non-hemolitik. Fraksinasi ECP teridentifikasi pada β-hemolitik sebanyak tujuh pita dan non-hemolitik empat pita protein. Konsentrasi protein sel utuh dan ECP b-hemolitik lebih besar dibandingkan bakteri non-hemolitik. Gejala abnormalitas lebih cepat terjadi pada ikan nila yang diinjeksi ECP bakteri b-hemolitik dan berbanding lurus dengan kematian sebanyak 91%-100% pada jam ke-13 pascainjeksi. Hasil ini menunjukkan bahwa ECP bakteri S. agalactiae β-hemolitik lebih virulen dibandingkan tipe non-hemolitik. Hingga akhir pemeliharaan tidak ada kematian pada ikan yang diinjeksi sel utuh bakteri S. agalactiae b-hemolitik dan non-hemolitik. Studi histopatologi ikan yang diinjeksi ECP S. agalactiae pada organ hati, limpa, otak, dan ginjal menunjukkan adanya kongesti, hemoragi, dan nekrosis.The β-hemolytic and non-hemolytic biotype of Streptococcus agalactiae are the agents that cause streptococcosis infection which resulted in high mortality and major losses in tilapia culture. This study aimed to compare the toxicity of whole cell and extracellular product (ECP) b-hemolytic and non-hemolytic bacteria from injected tilapia. Characterization of S. agalactiae was based on SNI and API 20 STREP and protein separation by SDS-PAGE method. Toxicity test was carried out by injecting whole cells and ECP S. agalactiae intraperitoneally with a dose of 0.1 mL fish-1. The results of biochemical tests, with confirmation by API 20 STREP showed that all isolates were positive for S. agalactiae. Protein fractionation of whole bacterial cells obtained as many as nine and seven bands of protein in b-hemolytic and non hemolytic biotype, respectively. ECP fractionation was identified in β-hemolytic biotype as many as seven bands and four protein bands in non-hemolytic. The whole cell protein concentration and ECP β-hemolytic were higher than non-hemolytic bacteria. Symptoms of abnormalities occurred faster in tilapia which was injected with ECP b-hemolytic bacteria and had positive correlation with 91%-100% mortalities at the 13th hours post-injection. This results indicated that ECP of S. agalactiae β-hemolytic are more virulent than non-hemolytic. Until the end of the trial, there were no deaths in fish injected with whole cells of b-hemolytic and non-hemolytic S. agalactiae. Histopathological studies of ECP-injected fish S. agalactiae in the liver, spleen, brain, and kidneys showed congestion, hemorrhage, and necrosis.