POLA INFEKSI Streptococcus agalactiae STRAIN NP105O DAN N14G PADA IKAN NILA (Oreochromis niloticus)
Authors: Suhermanto Achmad , Suhermin Suhermin , Ridwan Ridwan , Astuti Indri , Nurmawanti Iis 
Published: April 2020

Infeksi Streptococcosis yang disebabkan oleh bakteri patogen Streptococcus agalactiae dengan karakteristik strain berbeda menjadi permasalahan utama pada budidaya ikan nila. Penelitian ini bertujuan untuk menelaah pola infeksi bakteri S. agalactiae strain NP105O dan N14G, melalui performa organ target, gejala klinis, serta hematologi ikan nila Oreochromis niloticus. Karakterisasi S. agalactiae berdasarkan pada SNI dan API 20 STREP, uji pertumbuhan bakteri dilakukan dengan metode total plate count (TPC). Pengujian eksistensi bakteri dengan cara menginjeksikan S. agalactiae secara intraperitoneal (IP) dengan konsentrasi 107 CFU.mL-1, dan pengamatan dilakukan dengan pengambilan darah dan dikultur di media BHIA. Hasil uji biokimia dan konfirmasi menggunakan API 20 STREP menunjukkan bahwa isolat terkonfirmasi positif sebagai S. agalactiae, dan NP105O dideteksi sebagai bakteri â-hemolitik. Pertumbuhan bakteri NP105O lebih cepat daripada N14G, namun eksistensi di darah masing-masing selama 72 jam dan 24 jam. Hasil pengamatan performa darah menunjukkan bahwa glukosa dan leukosit mengalami peningkatan signifikan masing-masing 53,5 ± 2,12 mg.dL-1 dan 6,51 ± 0,89 (105 sel.mm-3), sedangkan hematokrit dan eritrosit mengalami penurunan signifikan (P<0.05) masing-masing 21,10 ± 0,07% dan 14 ± 4,5 (105 sel.mm-3) pascainjeksi S. agalactiae. Gejala klinis pascainfeksi berupa melanosis, respons lambat, anorexia, ocular opacity, purulens, unilateral atau bilateral eksoptalmia, gasping, erratic, C-shape, dan whirling. Pola infeksi S. Agalactiae strain NP105O dan N14G berbeda pada ikan nila, dan sangat dipengaruhi oleh keberadaan bakteri pada organ ginjal, otak, dan mata.Streptococcosis infection caused by different strains of pathogenic bacteria Streptococcus agalactiae has been a major problem in tilapia culture. This research aimed to examine the patterns of S. agalactiae infection of NP105O and N14G strains, through targeted organ performance, clinical symptoms and hematological signs of tilapia, Oreochromis niloticus. The characterization of S. agalactiae was based on SNI and API 20 STREP. Bacterial growth test was carried out using the total plate count (TPC) method. Bacterial infection was performed by injecting S. agalactiae intraperitoneally (IP) with a concentration of 107 CFU.mL-1, and the observations were carried out by extracting and culturing the fish blood in BHIA media. The result of the biochemical test and API 20 STREP confirmed that the isolates was identified as S. agalactiae and NP105O strain was detected as â-hemolytic bacteria. The growth of NP105O strain was faster than N14G strain, where their clear presence in blood was observed at 72 and 24 hours, respectively. The result of hematological parameters showed that glucose and leukocytes increased significantly with values of 53.5 ± 2.12 mg.dL-1 and 6.51 ± 0.89 (105 cell.mm-3), respectively. On the other hand, hematocrit and erythrocytes decreased significantly (P<0.05) 21.10 ± 0.07% and 14 ± 4.5 (105 cell.mm-3) post-S. agalactiae injection. Clinical signs post-infection consisted of melanosis, slow response, anorexia, ocular opacity, purulence, unilateral or bilateral exophthalmos, gasping, erratic movement, C-shape and whirling. NP105O, and N14G strains show different patterns of infections on tilapia and strongly influenced by the presence of bacteria in the kidneys, brain, and eyes.