Bacterial community associated to histamine contamination in sardines: a case study in the canned fish industry

This study aimed to identify the predominant bacterial populations in sardine samples with high histamine content (≥ 200 mg*kg-1) and histamine-free (< 1 mg*kg-1). For this study, 1,000 g of muscle samples were collected from 40–45 sardines per batch, all obtained from the same supplier, fishing area and period, for histamine analysis. Samples (1 g) from five different batches with ≥ 200 mg*kg-1 of histamine (named histamine group) and five with < 1 mg*kg-1 (named no-histamine group) were submitted to microbial analysis by extracting the total DNA, followed by polymerase chain reaction of the V3-V4 region of 16S rRNA gene and Ilumina sequencing (Mi-Seq, paired-end). In total, 18 different operational taxonomic units were identified in all samples. Sardines with high histamine content exhibited lower microbial diversity and a higher abundance of the genera Photobacterium and Shewanella. These bacteria thrive under mild temperatures and indicate fish spoilage and the production of biogenic amines. In contrast, Psychrobacter and Pseudoalteromonas, known to withstand harsh conditions, including low temperatures, were more prevalent in histamine-free sardines. Our findings point out to a marked change in the bacterial community of sardines with high and no histamine content, even though they are from the same fishing area, period, and shipment.