Evaluation of microbial contamination and effects of storage in raw meat-based dog foods purchased online.

Feeding raw-meat-based diets to companion animals has become a widespread practice, and many owners are now accustomed to buying frozen ingredients online. The goals of this study were to assess the microbiological quality of raw-meat dog foods obtained from specialized websites and to evaluate the effects of storage at different temperatures for a few days. Twenty-nine raw dog food products were processed for quantitative bacteriology (i.e. total viable count, TVC; Escherichia coli; faecal coliforms, FC) and sulphite-reducing clostridia, and analysed for the presence of Salmonella spp., Listeria monocytogenes, Yersinia enterocolitica and Clostridium difficile. Every sample was examined right after the delivery (T0), after 24 to 48 hr and after 72 hr, both at 2°C and 7°C. At T0, the mean score for the TVC was 5.9 × 106  cfu/g (SD = 4.8 × 107  cfu/g), while those for E. coli and FC were 1.1 × 104  cfu/g (SD = 2.5 × 105  cfu/g) and 3.3 × 103  cfu/g (SD = 6.5 × 104  cfu/g) respectively. The samples stored at 2°C had a significant increase of all parameters (TVC: p < .01; E. coli: p = .03; FC: p = .04) through time. Noteworthy differences between the analyses performed at 2°C and 7°C were found for TVC (p < .01), being the samples considerably more contaminated at higher temperatures. No sample tested positive for Salmonella spp., while L. monocytogenes was isolated from 19 products, Y. enterocolitica from three products and Clostridium perfringens and C. difficile from four and six products respectively. The microbiological quality of raw-meat dog foods sold online appears to be poor, carrying considerable amounts of potentially zoonotic bacteria and reaching greater levels of bacterial contaminations if not kept at proper refrigeration temperatures and fed soon after defrosting.

A challenge test on Pseudomonas spp. as spoiling microorganism in fish fillets.

Fish fillets are highly susceptible to spoilage, with Pseudomonas spp. bacteria being among the main culprits. To maintain products' quality and safety, it is important to control the load of these microorganisms and understand their growth potential in fish fillets. However, setting up challenge tests might be hard due to the difficulty of differentiating intentionally inoculated bacteria from those already present on the fillets. To overcome this obstacle, a pilot study using Pseudomonas aeruginosa, a clinically significant bacterial species that is rare in food, was conducted. Vacuum-packed Northern cod, salmon, and plaice fish fillets were experimentally inoculated and subjected to trials at both refrigeration (4 °C) and thermal abuse temperatures (from +4 °C to +6 °C and then to +8 °C). The results showed that the growth potential of Pseudomonas aeruginosa in all the fish fillets was less than 0.5 Log10 CFU/g. This confirms that vacuum packaging could reduce the multiplication of Pseudomonas spp. in the fish fillets and underlines as it is crucial to have fish fillets containing initial loads of Pseudomonas between 104-105 CFU/g or lower at the beginning of the shelf life in order to control the deterioration rate of the product. This study provides a basis for developing further challenge tests for Pseudomonas spp. in the fish industry and highlights the importance of controlling initial loads of Pseudomonas to prevent product deterioration during the shelf life.