Discovery and sequence analysis of four new types of toxin coregulated pilus A(tcpA)subunit gene of Vibrio cholerae

  Objective   To study the characteristic of toxin coregulated pilus Asubunit gene of Vibrio cholerae(VC) strains isolated from China.

  Methods   To use polymerase chain reaction(PCR)and the restriction fragments length polymor phism(RFLP), type specific primers PCR, sequencing and sequence analysis method differentially.

  Results   The type of toxin coregulated pilus Asubunit gene(tcpA)of 200 toxic EIT or biotype(EVC)strains and 100 toxic O.39 serogroup strains was the same as t2 type of EVC international reference strain N 16961.Four new types were found in non-toxic VC strains.Three of fifty non-toxic EVC strains contain tcpA gene, one contains t2 type, others contain two new types.None of non tox ic O139 strains contains tcpA gene.Two of 20 non-O1 non-O139 strains contain two new types of tcpA gene.The identity of tcpA genes of four new types found in this study and four types found by others was from 58.3% to 77.5%.The identity of TcpA of eight types was from 61.0% to 85.5%.The identity in 102 bp of 5 half of tcpA gene was high, and that in 210 bp of 3 half was low.The identity in 34 amino acids of Nhalf of TcpA was 100%, and that in 70 of Chalf was low.

  Conclusion  

  Methods   constructed can differentiate different type of tcpA gene of Vibrio cholerae accurately and rapidly.Four new types are found in non-toxic strains.