PATOGEN VIBRIO PADA KAKAP PUTIH (LATES CALCARIFER, BLOCH): SKRINING MEDIA DAN IDENTIFIKASI MOLEKULER

Abstrak

This study aims to identify the type of Vibrio pathogenic bacteria that attack white snapper (Lates calcarifer, Bloch) through selective media screening and molecular analysis. Fish samples were taken from a cultivation unit in Hurun Bay, Lampung, with clinical symptoms such as frayed fins and reddish skin. Isolation was carried out using TCBS and CHROMagar™ Vibrio media, followed by biochemical identification with Oxoid Microbact™ and molecular confirmation using polymerase chain reaction (PCR). The results showed 14 isolates positive for Vibrio sp. in the 16S rRNA gene (700 bp). A total of 11 isolates were identified as Vibrio alginolyticus through the collagenase gene (737 bp), one isolate as Vibrio parahaemolyticus with the ToxR gene (368 bp), and two isolates as Photobacterium damselae with the P.dam 5a gene (517 bp). Challenge tests against P. damselae showed an LD₅₀ value of 4.46 × 10⁷ CFU/ml per fish and caused mortality of up to 50% within 18 hours post-infection, with clinical symptoms including changes in body color, dorsal lesions, and swelling of internal organs. These results confirm the presence of various pathogenic Vibrio species in white snapper and the importance of verification with molecular identification for rapid and accurate diagnosis in controlling vibriosis in marine aquaculture.