Skin Culturable Microbiota in Farmed European Seabass (Dicentrarchus labrax) in Two Aquacultures with and without Anibiotic Use

This study examined culturable skin microbiota that was associated with farmed European seabass (Dicentrarchus labrax). Healthy European seabass were sampled during summer commercial harvest from one conventional fish farm where antibiotics are used, and from another practicing a certified antibiotic-free fish aquaculture. Physicochemical and microbiological analysis of seawater and sediment were performed, as well as determination of culturable bacteria, including Vibrio, from skin swabs of European seabass and seawater and sediment at both farms. Samples were processed for isolation of bacteria and their characterization by molecular and antibiotic susceptibility tests. In both fish farms, most of the bacteria that were identified in the skin belonged to the genera Pseudomonas and Vibrio. Some of the microbiota that were identified are known to be pathogenic to fish: V. alginolyticus, V. anguillarum, and V. harveyi. Vibrio strains showed higher resistance to certain antibiotics compared to previous studies. This study provides, for the first time, information on the culturable skin bacteria that is associated with healthy European seabass under culture conditions with and without the use of antibiotics. This information will be useful in assessing how changes in culturable microbiota may affect the health of farmed European seabass, indicating a potential problem for fish health management during disease outbreaks

AQUAHEALTH: Physiochemical parameters and Vibrio spp. abundance in water samples gathered in the Adriatic Sea

The genus Vibrio includes > 60 species that are autochthonous and ubiquitous aquatic microorganisms, members of the bacterial community in marine environments worldwide. Given their impact on human and animal health and the relative ease of their cultivation, Vibrio species have been well studied: the genus includes human and animal pathogens that have caused major diseases around the world (e.g. cholera or vibriosis). The dataset contains Vibrio spp. abundance and measurements of environmental parameters (temperature, salinity, total dissolved solids, pH, dissolved oxygen, total nitrogen, total phosphorus, total particulate matter, particulate organic matter and particulate inorganic matter), gathered at Mali Ston Bay in the Adriatic Sea. Water sampling was conducted at two locations: a floating cage fish farm (located near small island Maslinovac) and a control site (near island Pučenjak) at different depths (0.5 m, 5 m, 10 m and 18 m). The sampling period covers seasonal measurements between 2016 and 2019

Assessment of microbial sea water quality and health status of farmed European seabass (Dicentrarchus labrax) in Eastern Adriatic Sea (Montenegro and Croatia)

Semi-enclosed bays are generally considered important environmental resources for mariculture. This study was conducted within cage fish farms in two semi-enclosed bays of the Eastern Adriatic Sea, at Boka Kotorska Bay (Montenegro), and at Mali Ston Bay (Croatia). A total of 16 sea water samples, and 46 swabs from the gills and skin of European seabass were collected from two sea bass farms during two samplings in autumn and spring. The aim of this study was to determine the health status of European seabass in Montenegro and Croatia, to evaluate the environmental conditions in both farming areas, and to assess the presence of Vibrio and its impact on fish health. Most of the isolated bacteria from the samples were Gram-negative and comprised of Vibrio, Photobacterium and Pseudomonas genera. Assessment of fish health status showed that fish were clinically healthy and results present a bacterial community associated with healthy farmed European seabass. At the same time, some of the isolated bacterial strains are known to be pathogenic (V. alginolyticus, V. harveyi, V. anguillarum, P. damselae), and present a potential reservoir of infection. Simultaneous survey confirmed microbial impact in both bays due to an anthropogenic influence. The approach presented in this study is valuable in the assessment of farming conditions in semi-enclosed aquatic environments and is easily applicable to other similar locations worldwide

Characterization of Vibrio Populations from Cultured European Seabass and the Surrounding Marine Environment with Emphasis on V. anguillarum

Vibrio species are widely distributed and can be potentially pathogenic to aquatic organisms. In this study, we isolated Vibrio spp. from environmental samples (seawater, sediment, and fish swabs) collected over a three-year period from a fish farm in Mali Ston Bay in the Adriatic Sea, Croatia, and assess their distribution. A total of 48 seawater samples and 12 sediment samples, as well as gill and skin swabs from 110 farmed European seabass, were analysed for the presence of Vibrio. Vibrio strains were identified to the species level by MALDI TOF MS. The analysis revealed that V. alginolyticus was the predominant species in European seabass, followed by V. anguillarum. V. alginolyticus was isolated from the sediments, along with V. gigantis and V. pomeroyi, while V. chagasii, V. cyclitrophicus, V. fortis, V. gigantis, V. harveyi, V. pelagius, and V. pomeroyi were isolated from seawater. V. anguillarum was isolated only twice during two different spring seasons, once from a diseased sea bass and the second time from a healthy sea bass. We analysed these two isolates and found that they differ both genetically and in terms of resistance to antibiotics. Our results confirm the seasonality of vibriosis incidence and the presence of the pathogenic V. anguillarum, which increases the risk of vibriosis