Identification and histamine formation of Tetragenococcus isolated from Thai fermented food products

Forty-one tetrad-forming halophilic lactic acid bacteria were isolated from 7 kinds of fermented foods in Thailand. All the isolates were identified as the genus Tetragenococcus by their phenotypic characteristics. On the basis of 16S rRNA gene restriction analysis using MboI and AluI and 16S rRNA gene sequence analyses, 41 isolates could be divided into two groups (groups A and B). All 22 isolates in Group A were identified as T. halophilus. 16S rRNA gene sequences of the representative isolates, SP37-2 and KS87-1 exhibited 99.4–99.5 % similarity to that of T. halophilus ATCC 33315T. Nineteen isolates in Group B were identified as T. muriaticus. 16S rRNA gene sequences of the representative isolates, KM1-5 and KS87-14, showed 99.0–99.6 % similarity to that of T. muriaticus JCM 10006T. Histamine formation was determined by using HPLC and the histidine decarboxylase (hdc) gene of the newly isolated histamine-producing strain was partially sequenced. The strain KS87-14 prolifically formed histamine 10 times higher than the reported T. muriaticus JCM 10006T. The positive detection of KS87-14 was achieved by using hdcA gene-specific primers JV16HC and JV17HC.