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

Abstract

<p align="center"><strong>ABSTRACT</strong></p><p class="Default"><em> </em></p><p><em>Streptococcus agalactiae </em>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 <em>S. agalactiae </em>vaccine from N<sub>3</sub>M and N<sub>4</sub>M strain and examine the protective immunity against <em>S. agalactiae</em> N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1, </sub>and N<sub>14</sub>G 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 <em>S. agalactiae</em> strains that used were N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1</sub>,and N<sub>14</sub>G. Fry tilapia was vaccinated through intraperitoneal injection method with 0.1 mL per fish of N<sub>3</sub>M and N<sub>4</sub>M vaccines. Fish reared in aquarium sizing of 60×30×50 cm<sup>3</sup> with a density of 10 fishes aquarium<sup>-1</sup>. Two weeks after vaccination, fry tilapia was tested with 0.1 mL fish<sup>-1</sup> of each N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1</sub>, and N<sub>14</sub>G strains through intraperitoneal injection method. Antibody level measured with indirect enzym-linked immunosorbent assay<em> </em>(ELISA) method. The result of antibody level in vaccinated fish after vaccination of N<sub>3</sub>M, N<sub>4</sub>M vaccine, N<sub>3</sub>M and N<sub>4</sub>M control were 0.767; 0.743; 0.587; and 0.544, respectively. Relative percent survival in N<sub>3</sub>M vaccinated fish after challenged with N<sub>3</sub>M and N<sub>4</sub>M was 87.50% dan 64.70%, respectively, otherwise in N<sub>4</sub>M vaccinated fish was 62.50% dan 76.47%, respectively. N<sub>3</sub>M and N<sub>4</sub>M vaccine strain have better protection as only if it tested with similar bacteria strain.</p><p> </p><p>Keywords: formalin-killed cell, tilapia, protection, <em>S</em><em>treptococcus</em><em> </em><em>agalactiae</em>, strains</p><p><strong> </strong></p><p><strong> </strong></p><p align="center"><strong>ABSTRAK</strong></p><p align="center"><strong> </strong></p><p class="Paragraf"><em>Streptococcus agalactiae</em> 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 <em>S. agalactiae </em>strain N<sub>3</sub>M dan N<sub>4</sub>M serta mengkaji imunitas protektif terhadap infeksi <em>S. agalactiae </em>strain N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1</sub>, dan N<sub>14</sub>G. Benih ikan nila yang digunakan memiliki bobot 7,086±0,948 g dan panjang 7,443±0,353 cm. Bakteri yang digunakan adalah <em>S. agalactiae </em>strain N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1</sub>,danN<sub>14</sub>G. Benih ikan nila divaksinasi menggunakan metode injeksi pada bagian intraperitoneal sebanyak 0,1 mL ekor<sup>-1</sup> vaksin N<sub>3</sub>M dan N<sub>4</sub>M. Pemeliharaan dilakukan pada akuarium berukuran 60×30×50 cm<sup>3</sup> dengan kepadatan 10 ekor akuarium<sup>-1</sup>. Dua minggu setelah vaksinasi benih ikan diuji tantang dengan strain bakteri N<sub>3</sub>M, N<sub>4</sub>M, N<sub>17</sub>O, NK<sub>1</sub>, <sub> </sub>danN<sub>14</sub>G menggunakan metode injeksi pada bagian intraperitoneal dengan dosis 0,1 mL ekor<sup>-1</sup>. Level antibodi diukur dengan metode <em>indirect enzym-linked immunosorbent assay </em>(ELISA). Hasil menunjukkan level antibodi ikan setelah vaksinasi pada perlakuan vaksin N<sub>3</sub>M, N<sub>4</sub>M, kontrol N<sub>3</sub>M, dan kontrol N<sub>4</sub>M berturut-turut 0,767; 0,743; 0,587; dan 0,544. Kelangsungan hidup relatif ikan yang divaksin N<sub>3</sub>M setelah diuji tantang dengan strain N<sub>3</sub>M dan N<sub>4</sub>M berturut-turut 87,50% dan 64,70%, sedangkan pada ikan yang divaksin N<sub>4</sub>M berturut-turut 62,50% dan 76,47%. Vaksin strain N<sub>3</sub>M dan N<sub>4</sub>M memiliki proteksi lebih baik jika diuji tantang dengan strain bakteri yang sama.<em></em></p><p class="Default"> </p><p class="Paragraf">Kata kunci: <em>formalin-killed cell</em>, <em>Streptococcus agalactiae</em>, strain, proteksi, nila</p><p> </p><p> </p>