Journal of Microbiology

Research Support, Non-U.S. Gov'ts

Multilocus Sequence Typing and Virulence Factors Analysis of Escherichia coli O157 Strains in China: Xiao W. Ji , Ya L. Liao , Ye F. Zhu , Hai G. Wang , Ling Gu , Jiang Gu , Chen Dong , Hong L. Ding , Xu H. Mao , Feng C. Zhu , Quan M. Zou; J. Microbiol. 2010;48(6):849-855. Published online January 9, 2011; DOI: https://doi.org/10.1007/s12275-010-0132-8

Abstract: Escherichia coli O157:H7, an important food-borne pathogen, has become a major public health concern worldwide. The aim of this study was to investigate the molecular epidemiologic feature of E. coli O157:H7 strains in China. 105 E. coli O157:H7 isolates were collected from various hosts and places over 9 years. A multilocus sequence typing scheme (MLST) was applied for bacteria genotyping and polymerase chain reaction (PCR) was used for virulence factor identification. Seven new MLST sequence types (STs), namely ST836, ST837, ST838, ST839, ST840, ST841, and ST842 were identified, which grouped into two lineages. Phylogenetic analysis suggested that the most two frequent STs in China, ST837 and ST836, may be the derivatives of E. coli O157:H7 Sakai or E. coli O157:H7 EDL933. Geographical diversity and host variety of E. coli O157:H7 were observed in China. In addition, the different distribution of tccp was detected. The data presented herein provide new insights into the molecular epidemiologic feature of E. coli O157:H7, and aid in the investigation of the transmission regularity and evolutionary mechanism of E. coli O157:H7.

Fusion Expression and Immunogenicity of EHEC EspA-Stx2A1 Protein: Implications for the Vaccine Development: Yan Cheng , Youjun Feng , Ping Luo , Jiang Gu , Shu Yu , Wei-jun Zhang , Yan-qing Liu , Qing-xu Wang , Quan-ming Zou , Xu-hu Mao; J. Microbiol. 2009;47(4):498-505. Published online September 9, 2009; DOI: https://doi.org/10.1007/s12275-009-0116-8

Abstract: Shiga toxin 2 (Stx2) is a major virulence factor for enterohemorrhagic Escherichia coli (EHEC), which is encoded by λ lysogenic phage integrated into EHEC chromosome. Stx2A1, A1 subunit of Stx2 toxin has gathered extensive concerns due to its potential of being developed into a vaccine candidate. However, the substantial progress is hampered in part for the lack of a suitable in vitro expression system. Here we report use of the prokaryotic system pET-28a::espA-Stx2A1/BL21 to carry out the fusion expression of Stx2A1 which is linked to E. coli secreted protein A (EspA) at its N-terminus. Under the IPTG induction, EspA- Stx2A1 fusion protein in the form of inclusion body was obtained successfully, whose expression level can reach about 40% of total bacterial protein at 25°C, much higher than that at 37°C. Western blot test suggested the refolded fusion protein is of excellent immuno-reactivity with both monoclonal antibodies, which are specific to EspA and Stx2A1, respectively. Anti-sera from Balb/c mice immunized with the EspA-Stx2A1 fusion protein were found to exhibit strong neutralization activity and protection capability in vitro and in vivo. These data have provided a novel feasible method to produce Stx2A1 in large scale in vitro, which is implicated for the development of multivalent subunit vaccines candidate against EHEC O157:H7 infections.

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