Molecular identification of causative bacterial disease in giant gourami (Osphronemus goramy) based on 16S rRNA gene from extensive fishpond in Banjarnegara Regency, Indonesia

Abstract

The outbreak of bacterial disease often occurs in giant gourami (Osphronemus goramy) fish cultures. Banjarnegara Regency is the center of production of giant gourami (O. goramy) in Central Java, Indonesia. Thus, this research aimed to address the causative bacterial agent in giant gourami, based on 16S rRNA gene sequences. Twelve moribund fishes were collected from traditional fishponds of Banjarnegara Regency for bacterial isolation, and 440 juveniles were used to conduct Postulat Koch. Results showed that 21 bacterial isolates (SJB 01 – SJB 21) were isolated from kidney and external wounds of fishes from both GSP and TSA media. Postulate Koch assay indicated that four isolates (SJB 02, SJB 03, SJB 12, and SJB 14) led to fish mortality up to 60%, whereas illness was about 20% – 80%. Therefore, these isolates were potentially the causative agent of bacterial diseases in giant gourami. Based on the analysis of the 16S rRNA gene, the isolate SJB 02, SJB 03, SJB 12, and SJB 14 were closely related to Aeromonas hydrophilla (97.55%), Aeromonas veronii (98.92%), Pseudomonas otitidis (98.45%), and Aeromonas jandaei (97.74%), respectively.