Quantitative study, identification and antibiotics sensitivity of someVibrionaceae associated to a marine fish hatchery

This study characterises the bacteria associated with a marine hatchery in Tunisian coastal marine waters. Presumptive vibrios (TCBS agar) and heterotrophic aerobic microflora (CFU) were studied at different stages within the hatchery: seawater, batches of algal cultures, rotifers and Artemia culture tanks. The bacterial strains were isolated on TCBS Agar plates and described using different bacteriological tests (standardised micromethods “API 20 E Strips”, exoenzymes production, growth at different temperatures, pH and salinity, vibriostatic agent O/129 and antibiotics susceptibility). Two dominant genera of bacteria were found ( Vibrio and Aeromonas ) associated with some strains of the Pseudomonadaceae family. Vibrio alginolyticus was the dominant bacteria (75% of total isolates) found in rotifers ( Brachionus plicatilis ) and Artemia cultures ( Artemia salina ). In larvae rearing tanks, an increase of Vibrionaceae was noted after larvae were fed with Artemia . Most of the studied bacteria used the skin mucus of Sparus aurata larvae as their sole source of carbon. All the V. alginolyticus strains were β-haemolytic, hydrolyse the DNA and were susceptible to several tested antibiotics.