Prevalence of Histidine Decarboxylase Genes of Gram-Positive Bacteria inSurstrommingas Revealed by qPCR

Histamine is a degradation product of the bacterial decarboxylation of the amino acid histidine; such activity is determined by histidine decarboxylase encoded by a gene cluster, carried by some Gram-positive bacteria, that includes thehdcAgene. In this study, the presence of thehdcAgene in ready-to-eatsurstrommingsamples collected from three producers based in Sweden was directly assessed via qPCR analysis for the very first time. Samples from producer A showedhdcAaverage gene abundance of 6.67 +/- 0.13 Log cells/gene copies g(-1); in samples from producer B the average value attested at 5.56 +/- 0.06 Log cells/gene copies g(-1), whereas for samples of producer ChdcAaverage gene abundance attested at 5.30 +/- 0.08 Log cells/gene copies g(-1). ANOVA showed a significantly higher averagehdcAgene copy number in samples from producer A, whereas no significant differences were seen between average values ofhdcAgene copy numbers detected in samples from producer B and C. ThehdcAgene copies detected in the present study could give an estimation of the load of potential histamine-producing bacteria insurstromming.