Pathogenicity and antibiotic susceptibility of Vibrio species isolated from the captive–reared tropical marine ornamental blue damsel fish, Pomacentrus caeruleus (Quoy and Gaimard, 1825)

Microbiological assessment of vibriois infected blue damsel, Pomacentrus caeruleus reared in captivity in marine aquaria led to isolation of five distinct Vibrio species. Cultural, morphological and biochemical characteristics of these isolates identified them as Vibrio alginolyticus (29.4%), V. vulnificus (26.8%), V. fluvialis (15.3%), V. pelagius (9.1%) and V. anguillarum (19.4%). Predominant Vibrio alginolyticus and V. vulnificus were tested for pathogenicity and Koch postulate by experimentally infecting apparently healthy blue damsels, P. caeruleus. The lethal dose (LD50) was 1.36×10 6 and 3.44×10 CFU/g fish (colony forming units) for V. alginolyticus and V. vulnificus respectively. All the vibrios were highly susceptible to the broad spectrum antibiotics Chloramphenicol (30 μg/disc), Erythromycin (15 μg/disc), Gentamycin (30 μg/disc) and Oxytetracycline (30 μg/disc).