| Summary: | Microorganisms may colonize the skin, gills and the gut of fish reflecting the bacterial load of aquatic environment. Altogether 22 samples of freshwater fish, including European perch (Perca fluviatilis n=7), silver bream (Blicca bjoerkna n=4) and European eel (Anguilla anguilla n=11) were collected during September 2014 from Usma lake in Latvia. Samples of gills, skin and gut of each fish were examined for the Total Bacterial Count (TBC), Enterobacteriaceae, fecal coliforms and psychrotrophic bacteria count. Pooled samples of skin, muscles, gut and internal organs from each fish were investigated for the presence of Salmonella spp., Listeria spp. and Yersinia spp. The highest count of TBC was found on skin of silver bream -7.96 log10 cfu cm-2, while the lowest in gut of European eel - 2.16 log10 cfu g-1. Also the highest count of Enterobacteriaceae was found on European perch skin (6.63 log10 cfu cm-2). The lowest count of Enterobactericeae was found on skin of European eel (0.41 log10 cfu cm-2). Number of fecal coliforms was higher on skin of silver bream - 5.43 log10 cfu cm-2. The lowest number of fecal coliforms was found in gills of European perch (3.42 log10 cfu g-1), while fecal coliforms were not isolated from European eel gut. Number of psychrotrophic bacteria was the highest in gills of European perch (6.23 log10 cfu g-1), but the lowest psychrotrophic bacteria counts were observed in gills of European eel (2.24 log10 cfu g-1). All samples were Salmonella spp., Listeria spp., Yersinia spp. negative. Contamination rates with TBC, Enterobacteriaceae, fecal coliforms and psychrotrophic microorganisms were significantly lower in eels (p<0.05) than in silver bream and European perch. Differences in microbiological contamination of tested samples could be linked to different ecology of fish.
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