Evaluation and identification of histamine-forming bacteria on fish products of middle Adriatic Sea

  • Claudia Costanza Dipartimento di Scienze Mediche Veterinarie, Università degli Studi di Bologna, Alma Mater Studiorum, via Tolara di Sopra 50, 40064 Ozzano Emilia, Italia., Italy.
  • Matilde Cecchini Dipartimento di Scienze Mediche Veterinarie, Università degli Studi di Bologna, Alma Mater Studiorum, via Tolara di Sopra 50, 40064 Ozzano Emilia, Italia., Italy.
  • Rocco Mancusi Dipartimento di Scienze Mediche Veterinarie, Università degli Studi di Bologna, Alma Mater Studiorum, via Tolara di Sopra 50, 40064 Ozzano Emilia, Italia., Italy.
  • Alcide Mosso Dipartimento di Sanità Pubblica AUSL Ferrara, Servizio Veterinario, via Borgoleoni, 128, Ferrara, Italy.
  • Gabriele Giani Dipartimento di Sanità Pubblica AUSL Imola, Servizio Veterinario, Viale Amendola, 8, Imola, Italy.
  • Roberto Rosmini Dipartimento di Scienze Mediche Veterinarie, Università degli Studi di Bologna, Alma Mater Studiorum, via Tolara di Sopra 50, 40064 Ozzano Emilia, Italia, Italy.
  • Marcello Trevisani | marcello.trevisani@unibo.it Dipartimento di Scienze Mediche Veterinarie, Università degli Studi di Bologna, Alma Mater Studiorum, via Tolara di Sopra 50, 40064 Ozzano Emilia, Italia., Italy.

Abstract

Regulation EU 2073/2005 sets maximum concentration for histamine in fish and products thereof. To meet these criteria, manufacturers have to define performance objectives, such as the maximum allowed prevalence and number/activity of histamine-producing bacteria at relevant stage of production. In order to assess the presence and decarboxylase activity of contaminant bacteria we examined 51 samples of blue fish caught and processed in Emilia Romagna region. We collected 50 gr of fish (skin and gills or the entire product) from 10 sample units from every lot. Analytical samples were cultured in Trypticase Soy Broth supplemented with histidine and pyridoxal HCl. Histamine was measured with an electrochemical biosensor after incubation at both 37°C for 24 h and 18-22°C for 48 h. Enrichments that showed relevant enzymatic activity were seeded on Niven agar to isolate suspected colonies and DNA extracts from these bacteria were analyzed by polymerase chain reaction (PCR) for detecting specific sequences of the gene encoding pyridoxaldependent histidine decarboxylase (HDC). Overall, 29.4% samples showed relevant production of histamine in broth cultures (above a cut-off value set at 250 ng/mL) and 53.3% of them (8 out of 15 samples) allowed detection of HDC positive strains. All of them were typed as Morganella, which appears to be the most common of fish caught in middle Adriatic sea. Ten out of the twelve positive samples with enrichment cultures incubated at both 37 and 18-22°C (83%) showed higher decarboxylase activity at room temperature, suggesting the presence of psychrotolerant strains. In addition, the prevalence of histamine-producing bacteria was higher at retail than at production level, probably as a consequence of manipulations and cross-contamination. The risk correlated to development of histamine-producing psychrotolerans bacteria cannot be controlled only with storage temperature: it is necessary for the food business operators to evaluate specific performance objectives, define useful parameters to qualify suppliers, and guarantee microbiological criteria fixed by Regulation EU 2073/2005.

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Published
2013-04-18
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Original Articles
Keywords:
Morganella morganii, Morganella psychrotolerans, Histidine decarboxylase, Histamine, Shelf life, Fish poisoning
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How to Cite
Costanza, C., Cecchini, M., Mancusi, R., Mosso, A., Giani, G., Rosmini, R., & Trevisani, M. (2013). Evaluation and identification of histamine-forming bacteria on fish products of middle Adriatic Sea. Italian Journal of Food Safety, 2(1), e7. https://doi.org/10.4081/ijfs.2013.944