Efficacy of Streptococcus agalactiae vaccine strains N3M and N4M in fry tilapia infected by different strains of S. agalactiae

Abstract

ABSTRACT

Streptococcus agalactiae is a major bacterial streptococcosis disease that infects tilapia. This study aimed to analyze a specific and nonspecific immune system in fry tilapia that has been given with S. agalactiae vaccine from N₃M and N₄M strain and examine the protective immunity against S. agalactiae N₃M, N₄M, N₁₇O, NK_1,  and N₁₄G strains infection. Fry tilapia used in this study has the weight of 7.086±0.948 g and length of 7.443±0.353 cm. The S. agalactiae strains that used were N₃M, N₄M, N₁₇O, NK₁,and N₁₄G. Fry tilapia was vaccinated through intraperitoneal injection method with 0.1 mL per fish of N₃M and N₄M vaccines. Fish reared in aquarium sizing of 60×30×50 cm³ with a density of 10 fishes aquarium^-1. Two weeks after vaccination, fry tilapia was tested with 0.1 mL fish^-1 of each N₃M, N₄M, N₁₇O, NK₁, and N₁₄G strains through intraperitoneal injection method. Antibody level measured with indirect enzym-linked immunosorbent assay (ELISA) method. The result of antibody level in vaccinated fish after vaccination of N₃M, N₄M vaccine, N₃M and N₄M control were 0.767; 0.743; 0.587; and 0.544, respectively. Relative percent survival in N₃M vaccinated fish after challenged with N₃M and N₄M was 87.50% dan 64.70%, respectively, otherwise in N₄M vaccinated fish was 62.50% dan 76.47%, respectively. N₃M and N₄M vaccine strain have better protection as only if it tested with similar bacteria strain.

Keywords: formalin-killed cell, tilapia, protection, Streptococcus agalactiae, strains

ABSTRAK

Streptococcus agalactiae merupakan bakteri utama penyakit streptococcosis yang menginfeksi ikan nila. Tujuan penelitian ini adalah menganalisis sistem imun spesifik dan nonspesifik pada benih ikan nila yang diberi vaksin S. agalactiae strain N₃M dan N₄M serta mengkaji imunitas protektif terhadap infeksi S. agalactiae strain N₃M, N₄M, N₁₇O, NK₁, dan N₁₄G. Benih ikan nila yang digunakan memiliki bobot 7,086±0,948 g dan panjang 7,443±0,353 cm. Bakteri yang digunakan adalah S. agalactiae strain N₃M, N₄M, N₁₇O, NK₁,danN₁₄G. Benih ikan nila divaksinasi menggunakan metode injeksi pada bagian intraperitoneal sebanyak 0,1 mL ekor^-1 vaksin N₃M dan N₄M. Pemeliharaan dilakukan pada akuarium berukuran 60×30×50 cm³ dengan kepadatan 10 ekor akuarium^-1. Dua minggu setelah vaksinasi benih ikan diuji tantang dengan strain bakteri N₃M, N₄M, N₁₇O, NK₁,  danN₁₄G menggunakan metode injeksi pada bagian intraperitoneal dengan dosis 0,1 mL ekor^-1. Level antibodi diukur dengan metode indirect enzym-linked immunosorbent assay (ELISA). Hasil menunjukkan level antibodi ikan setelah vaksinasi pada perlakuan vaksin N₃M, N₄M, kontrol N₃M, dan kontrol N₄M berturut-turut 0,767; 0,743; 0,587; dan 0,544. Kelangsungan hidup relatif ikan yang divaksin N₃M setelah diuji tantang dengan strain N₃M dan N₄M berturut-turut 87,50% dan 64,70%, sedangkan pada ikan yang divaksin N₄M berturut-turut 62,50% dan 76,47%. Vaksin strain N₃M dan N₄M memiliki proteksi lebih baik jika diuji tantang dengan strain bakteri yang sama.

Kata kunci: formalin-killed cell, Streptococcus agalactiae, strain, proteksi, nila