Uji Keganasan Bakteri Vibrio pada Ikan Kerapu Macan (Epinephelus fuscoguttatus)

Abstract

Tiga belas isolat bakteri Vibrio yang terdiri atas 6 spesies diuji keganasannya pada ikan Kerapu Macan (Epinephelus fuscoguttatus) sehat yang berukuran panjang 9 – 13 cm dan berat 20 – 30 g. Ke enam spesies
bakteri Vibrio yang diuji adalah Vibrio alginolyticus (6 isolat), V. vulnificus (2 isolat), V. ordalii (2 isolat) V. fluvialis, V. anguillarum dan V. mectnikovii masing masing 1 isolat. Bakteri Vibrio ini berasal dari ikan Kerapu sakit dan air tambak dari berbagai tempat di Indonesia. Uji keganasan dilakukan dengan menyuntikkan suspensi bakteri sebanyak 0,5 ml x 109 CFU/ml secara intramuskular di bagian dorsolateral. Jumlah ikan yang disuntik adalah 5 ekor/isolat. Ikan kontrol (5 ekor) disuntik dengan 0,5 ml PBS steril. Ikan dipelihara selama 2 minggu didalam akuarium (vol air 40 L) yang dilengkapi dengan aerator. Jumlah ikan yang mati, waktu kematian serta gejala klinis yang terlihat dicatat. Untuk memastikan sebab kematian dan mengkonfirmasikan keberadaan
bakteri vibrio yang disuntikkan, ikan yang mati dibedah dan bakteri diisolasi dari ginjal dan luka pada tubuh. Pada akhir penelitian semua ikan yang masih hidup dibunuh dan bakteri diisolasi dari ginjal. Bakteri hasil uji keganasan diidentifikasi dengan metoda biokimia. Semua isolat menyebabkan kematian pada ikan uji kecuali V.metchinovkii dan tidak ada ikan kontrol yang mati. Kultur murni isolat yang disuntikkan direisolasi dari semua ikan yang mati. Berdasarkan jumlah ikan uji yang mati dan waktu kematian isolat terdapat 4 isolat yang ganas yaitu V.anguillarum, V. ordalii (S) dan V. fluvialis (S) dan V. alginolyticus 8 (J). Gejala klinis ikan yang sakit sama yaitu nafsu makan berkurang, berenang miring dan lemah, ginjal pucat warna tubuh gelap. Beberapa
isolat menyebabkan luka di punggung yang berkembang jadi borok.

Kata kunci: keganasan, Vibrio, Kerapu, ikan, penyakit.

Thirteen isolates of Vibrio which consists of 6 spesies were tested its virulency on healthy fishes, Kerapu Macan (Epinephelus fuscoguttatus) with size 9 – 13 cm (tota length) and 20 – 30 g (weight). Those six
species of Vibrio were Vibrio alginolyticus (6 isolate), V. vulnificus (2 isolate), V. ordalii (2 isolate) V. fluvialis (1 isolate), V. anguillarum (1 isolate) and V. mectnikovii (1 isolate). These Vibrio were isolated from sick Kerapu and water pond from various places in Indonesia. The test was done by intramuscular injection of bacteria suspension i.e. 0,5 ml x 109 CFU/ml on the dorsolateral of the fish. The number of injected fish were 5 fish/isolate, while control fishes were injected with 0,5 ml of sterile PBS. The fishes were grown for 2 weeks on 40 L aerated aquariums. Mortality of the fish, time as well as clinical simptoms were recorded. The occurence of injected bacteria was confirmed by isolating the bacteria from the kidney and wound of the dead fishes At the end of the experiment all the live fishes were killed and bacteria on its kidney were isolated. All the
bacteria were identified by using biochemical method. The results showed that all isolates have caused mortality on the fish except V. metchinovkii as well as control fishes. Four other isolates were found to be virulence. Clinical simptoms of sick fishes were the same i.e. lack of feeding activity, abnormal swimming activity and weak, pale kidney, and dark colouration of the skin. Several isolates have caused wound on the back of the fish as well.

Key words: virulency, Vibrio, Kerapu, fish, diseases.