MICROFLORA ASSOCIATED WITH HEALTHY AND DISEASED TURBOT (SCOPHTHALMUS-MAXIMUS) FROM 3 FARMS IN NORTHWEST SPAIN

A comparative analysis of the microbiological quality of three turbot (Scophthalmus maximus) farms (A, B, and C) located in Galicia (northwe st Spain) is given. The microbial load and types of bacteria in the in ternal organs (liver and kidney) of apparently healthy fish was monito red over a year, and all the disease problems occurring during this su rvey were analyzed. The percentage of healthy turbot in which positive bacterial growth was obtained was relatively high in the three ongrow ing facilities. Farm A exhibited the poorest conditions of fish health with an average of 42% fish infected, while farm B showed the best mi crobiological quality with 27% of turbot harbouring bacteria in the in ternal organs. In all three farms, a wide range of bacteria was found in healthy turbot with Vibrio (V. splendidus-V. pelagius, V. fisheri-V . harveyi and Vibrio spp.) and Pseudomonas spp. being the predominant groups comprising at least 80% of the total bacterial isolates in each farm. The highest number of pathological problems (22) with the most diverse bacterial flora occurred in farm A. Vibrio spp. and Pseudomona s spp. were the most prevalent bacteria recovered from diseased turbot . Haemorrhages in palate and jaws, tail and fins, and ulcerative lesio ns were the most frequent external clinical signs of diseased fish rec orded in the three farms. However, it was not possible to associate a particular bacterial species with a specific pathology. Routine use in farm A of oxolinic acid and nitrofurantoin may have led to the develo pment in the Vibrio strains of resistances to both chemotherapeutants (up to 25%).