Bacterial microflora of roach (Rutilus rutilus) caught in the Driksna river in Latvia

Abstract

Fish and fish products are a food group with a high nutritional value, however, the fish may contains a variety of microorganisms, which may cause foodborne infection outbreaks in humans after consumption. The aim of the present study was to identify the bacterial microflora of skin, gill and gut of roach caught in river. Altogether, nine roach (Rutilus rutilus) samples were collected from fishermen from Driksna river in Latvia. Skin, gills and gut samples were investigated for total bacterial count (TBC), coliforms and Enterobacteriaceae. Pooled skin, muscles and internal organ samples were examined for presence of pathogens – Salmonella spp., Listeria spp. and Yersinia spp. in accordance with ISO standards. Identification of bacterial species was performed with MALDI-TOF MS Biotyper. TBC ranged from 1.96 to 5.16 log₁₀ CFU g^-1, coliforms from 0 to 3.66 log₁₀ CFU g^-1 and Enterobacteriaceae from 0 to 4.16 log₁₀ CFU g^-1 in roach skin, gills and gut samples. The highest counts of TBC, coliforms and Enterobacteriaceae was found in roach gills and gut samples, while there were no significant differences between the TBC in skin, gills and gut (p<0.05). Rahnella spp. and Pseudomonas spp. were the dominant bacteria identified in fish skin, gills and gut. These microorganisms promote the development of deterioration processes of fish meat, and also can be associated with human infections. Salmonella spp., Listeria spp. and Yersinia spp. were not detected in fish samples, however, the presence of potential human pathogens - Aeromonas spp. and Staphylococcus spp. in roach samples was observed.