Microbiological quality assessment of fresh tilapia marketed in the Federal District and of the ice used for its conservation

Tilapia (Oreochromis niloticus) is the most cultivated and consumed freshwater fish in Brazil. The present study aimed to evaluate the microbiological quality of ice and fresh tilapia samples commercialized in the Federal District. Tilapia samples were tested for counts of mesophilic and psychrotrophic bacteria, determination of total and thermotolerant coliforms, Staphylococcus aureus counts and presence of Salmonella. Ice samples were analyzed for determination of total coliforms and thermotolerant coliforms and presence of Escherichia coli. Of the 20 samples of fresh tilapia analyzed, ten samples (50%) presented Salmonella (genetically confirmed through the presence of the invA gene) and, therefore, were unfit for consumption. S. aureus was found in 11 samples (55%), and one sample of fillet presented S. aureus counts (3.15 CFU/g) above the limit allowed by Brazilian legislation (3 log CFU/g). S. aureus colonies were confirmed by detection of CoA gene in molecular analysis. Of the 14 ice samples analyzed, 12 samples (85.7%) were unfit for use in fish conservation due to the presence of total coliforms and 9 ice samples (64.3%) were also contaminated with thermotolerant coliforms. E. coli was isolated from 6 ice samples (42.9%) and confirmed in the molecular analysis through the amplification of the MalB gene. In conclusion, the high contamination of tilapia samples with Salmonella and of the ice used for its conservation with coliforms and E. coli indicates the need for better hygienic practices in the tilapia production chain, to increase its quality and microbiological safety.