Open AccessComparison of Shiga toxin-encoding bacteriophages in highly pathogenic strains of Shiga toxin-producing Escherichia coli O157:H7 in the UK
Author(s) -
Daniel Yara,
David R. Greig,
David L. Gally,
Timothy J. Dallman,
Claire Jenkins
Publication year - 2020
Publication title -
microbial genomics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.476
H-Index - 28
ISSN - 2057-5858
DOI - 10.1099/mgen.0.000334
Subject(s) - prophage , biology , shiga toxin , lineage (genetic) , bacteriophage , genetics , escherichia coli , insertion sequence , microbiology and biotechnology , population , virology , genome , gene , transposable element , demography , sociology
Over the last 35 years in the UK, the burden of Shiga toxin-producing Escherichia coli (STEC) O157:H7 infection has, during different periods of time, been associated with five different sub-lineages (1983-1995, Ia, I/IIa and I/IIb; 1996-2014, Ic; and 2015-2018, IIb). The acquisition of a stx2a -encoding bacteriophage by these five sub-lineages appears to have coincided with their respective emergences. The Oxford Nanopore Technologies (ONT) system was used to sequence, characterize and compare the stx -encoding prophages harboured by each sub-lineage to investigate the integration of this key virulence factor. The stx2a -encoding prophages from each of the lineages causing clinical disease in the UK were all different, including the two UK sub-lineages (Ia and I/IIa) circulating concurrently and causing severe disease in the early 1980s. Comparisons between the stx2a- encoding prophage in sub-lineages I/IIb and IIb revealed similarity to the prophage commonly found to encode stx2c , and the same site of bacteriophage integration ( sbcB ) as stx2c -encoding prophage. These data suggest independent acquisition of previously unobserved stx2a -encoding phage is more likely to have contributed to the emergence of STEC O157:H7 sub-lineages in the UK than intra-UK lineage to lineage phage transmission. In contrast, the stx2c -encoding prophage showed a high level of similarity across lineages and time, consistent with the model of stx2c being present in the common ancestor to extant STEC O157:H7 and maintained by vertical inheritance in the majority of the population. Studying the nature of the stx -encoding bacteriophage contributes to our understanding of the emergence of highly pathogenic strains of STEC O157:H7.