The increase in the demand for caviar has encouraged a rapid expansion of intensive sturgeon farming over the last twenty years. Likewise, to the increase in productions, the onset of infectious diseases has raised. Although it's known that viral infections represent the major cause of mortality in sturgeons, even bacterial diseases can be an important source of economic losses. Here we present data of a health monitoring aimed to characterize bacterial infections occurred in Northern Italy sturgeon farms between 2009 and 2017.
Sturgeon production for aquaculture has increased worldwide. In Italy since the nineties, it's very important mainly for caviar production. Despite this, there is limited information about diseases that affect sturgeon farming also in this country. Accordingly, in this study we describe cases of bacterial infection during a monitoring campaign carried out from 2009 to 2017. We analyzed samples from Russian sturgeon A. gueldenstaedtii, n = 725, Siberian sturgeon Acipenser baerii, n = 103, Adriatic sturgeon A. naccarii, n = 10, Sterlet sturgeon A. ruthenus, n = 16, White sturgeon A. transmontanus, n = 2, and Beluga sturgeon Huso huso, n = 2 from Northern Italian fish farming for a total of 858 samples. The subjects were necropsied under aseptic conditions and evaluated for the presence of lesions such as wounds, bleeding or other pathological alterations. Collection of samples for bacteriological exam was taken from kidney and brain using first isolation media (Columbia Blood Agar or TSA). The colonies grown after 24-72 hours of incubation at 22±2°C were selected, cloned in selective media and identified by biochemical tests using API galleries (API 20E and 20 NE, bioMérieux). Phenotypic bacteria identification was confirmed by Matrix-assisted laser desorption ionization-time of flight mass spectrometry (MALDI-TOF MS) technology on VITEK MS system (bioMérieux, France). The bacterial exam was positive in 297 individuals (34,61%) while the remaining 561 (65,39%) showed no bacterial growth. The isolated bacterial species were: Aeromonas hydrophila (37,71%), Plesiomonas shigelloides (17,17%), Aeromonas sobria (10,77%), Pseudomonas spp. (6,06%) Acinetobacter spp. (3,42%) and others in small percentage belonging to Citrobacter spp., Yersinia ruckeri, Aeromonas salmonicida, Vibrio spp., Flavobacterium spp. and Chryseomonas spp. No Gram+ bacteria have been isolated. The presence of many bacterial species implied a mixed infection of these fish, and hemorrhages are observed in all bacteria-infected fish, but external clinical signs are not pathognomonic for any isolated bacteria. The most isolated bacteria appearing low pathogenic. But even so, sometimes fish are predisposed to systemic gram-negative facultative bacterial infections resulting from handling trauma or adverse growth, and viral diseases. This knowledgebase is important as it will help create a bacterial profile of sturgeons reared in Italy.