Microbiological assessment of Sea bass (Dicentrarchus labrax) farmed in the Adriatic Sea (Croatia)

Sea bass (Dicentrarchus labrax) is an important fish species farmed in many countries, including Croatia. Farming of healthy and quality Sea bass is the main aim in Sea bass aquaculture. This study documents the bacteria associated with Sea bass aquaculture during regular normal farming. The study was carried out on a commercial marine farm in the Malostonski bay of the Adriatic Sea. During the sampling period in 2016 and 2017, in total 80 specimens of the Sea bass were collected seasonally (spring, summer, autumn and winter). Samples for microbiological analysis were taken as swabs from the gills and skin using the sterile cotton sticks. All swab samples were serially diluted, plated and incubated on Marine agar (22°C), CHROMagar™ Acinetobacter (37°C), Slanetz-Bartley (35°C), Pseudomonas agar F (22°C) and Thiosulphate Citrate Bile Salt Sucrose (22°C) for isolation. Representative colonies were picked for further identification by MLADI TOF MS. The bacterial genera were predominantly Gram-negative and comprised mostly of Pseudomonas, followed by Acinetobacter, Vibrio and Aeromonas. The other, less numerous bacteria are from the genera Achromobacter, Arthrobacter, Microbacterium, Pantoea, Photobacterium, Providencia and Shewanella. Because the quality of fresh Sea bass is a major concern for the consumers, obtained results should allow a better control of the bacteriological parameters in the Sea bass aquaculture and also better control of processing to reduce the possible microbial risk.