engleski

Ecology of Vibrio (Listonella) anguillarum isolated from Eastern Adriatic Sea (Croatia and Montenegro)

Among different species of Vibrio, Vibrio (Listonella) anguillarum is most commonly known as causative agent of vibriosis. Vibriosis is a major disease occurring in the marine aquaculture. The number of this infections at marine fish farms increased during recent years with significant morbidity and mortality within commercially important fish species. From that reason, various research groups have performed studies aimed to elucidating the pathogenesis of vibriosis. Despite these efforts, some questions regarding the pathogenesis of vibriosis remain open. Our study was carried out to determine ecology of the V. anguillarum isolates (complex interactions between the microorganism and its host and marine environment) and their resistance to various antibiotics. The samples (swabs from the skin and gills of European sea bass Dicentrarchus labrax, and marine water samples from the fish farm and control location) used for microbiological analysis were obtained from two marine aquacultures in the Eastern Adriatic located at Malostonski bay (Croatia) and the Bay of Kotor (Montenegro) in spring and autumn 2017/2018. Heterotrophic bacteria (HPC) and Vibrio were determined on Marine agar and Thiosulfate- Citrate-Bile-Sucrose Agar (TCBS). Microbial indicators: total coliforms and Escherichia coli, as well as enterococci were determined using Colilert® and Enterolert-E® tests. The results of microbial analysis showed that the numbers of bacteria (HPC and Vibrio) varied in different water quality conditions. V. anguillarum isolates from fish (Croatia) and marine water (Montenegro) samples were studied using MALDI TOF and molecular methods (sequencing). These isolates were further characterized using atomic force microscopy and their susceptibility to 13 antimicrobial agents by the disk diffusion method. Data on antibiotic resistance indicate that all isolates of V. anguillarum were resistant to ampicillin, oxytetracycline and vancomycin. In contrast to environmental isolates, fish isolates were resistant to gentamicin, erythromycin and streptomycin. These results show that fish samples isolates were more antibiotic resistant than environmental, indicating that some of tested antibiotics are commonly used in the fish treatment from the hatcheries to the farms. To the best of our knowledge, this is the first report on V. anguillarum isolation from marine water that provided new features of this fish pathogen not yet reported in literature.

Vibrio Listonella anguilarum ; Croatia ; Montenegro ; ecology

Diversity of Vibrio spp. in Mediterranean mussel (Mytilus galoprovincialis) originating from aquaculture environments in Montenegro and Croatia