Tracking spoilage bacteria in the tuna microbiome

Our study of the tuna microbiome has shown that the liver and gut of these fish are reservoirs of histamine-producing bacteria likely to present a health risk. Like other seafood products, tuna is highly perishable and sensitive to microbial spoilage. Its consumption, whether fresh or canned, can lead to severe food poisoning due to the activity of specific microorganisms, including histamine-producing bacteria. Yet, many grey areas persist regarding their ecology, conditions of emergence, and proliferation in fish. In this study, we used 16S rRNA barcoding to investigate postmortem changes in the bacteriome of fresh and brine-frozen yellowfin tuna (Thunnus albacares), until late stages of decomposition (i.e. 120 h). The results revealed that despite standard refrigeration storage conditions (i.e. 4 degrees C), a diverse and complex spoilage bacteriome developed in the gut and liver. The relative abundance of spoilage bacterial taxa increased rapidly in both organs, representing 82% of the bacterial communities in fresh yellowfin tuna, and less than 30% in brine-frozen tuna. Photobacterium was identified as one of the dominant bacterial genera, and its temporal dynamics were positively correlated with histamine concentration in both gut and liver samples, which ultimately exceeded the recommended sanitary threshold of 50 ppm in edible parts of tuna. The results from this study show that the sanitary risks associated with the consumption of this widely eaten fish are strongly influenced by postcapture storage conditions.

Automated summary

The study suggests that the liver and gut of tuna fish harbor histamine-producing bacteria that may pose a health risk. The research reveals that even under standard refrigeration conditions, a diverse and complex spoilage bacteriome forms in the gut and liver of the fish. The dominant bacterial genus, Photobacterium, is correlated with histamine concentration in both organs, exceeding the recommended sanitary threshold in edible parts of the tuna.