清水 健

ABSTRACT The complete genome sequence of Edwardsiella tarda strain GBS0709, isolated from an 81-year-old Japanese patient with the acute motor axonal neuropathy subtype of Guillain–Barré syndrome, was determined. It comprised a 3,632,068 bp circular chromosome and a 5,386 bp plasmid. The overall guanine and cytosine content was 57.3%.

Graphical Abstract

Eighty strains of enterohemorrhagic Escherichia coli O157:H7/H- were analyzed by three single-nucleotide polymorphism (SNP) panels using whole-genome sequencing data. The partial concordance of SNP types among the different SNP panels was observed on minimum spanning trees reconstructed with SNP data. As for lineage I/II strains, some of the clade 7 strains belonged to one unique SNP type as determined by three panels, suggesting that clade 7 should be divided into at least two genotypes, namely, the unique type and the rest. In addition, clade 8 contained two unique genotypes, which was consistent with the previous prediction. Similarly, for lineage II, clade 12 should be divided into three genotype strains. In contrast, many strains of several clades belonging to lineage I were clustered into the same node on each minimum spanning tree upon testing with the three SNP panels. Previous studies reported that lineage I diverged more recently than lineages I/II and II. Such low diversity in lineage I in this study may have arisen because this lineage has not accumulated SNPs because of its relatively recent divergence. Based on the concordance observed in this study, some of the previously published O157 genotype distribution data were successfully interpreted to clarify the clade distribution, which was well supported by previous literature.

Enterohaemorrhagic <italic> <named-content content-type="species"> <ext-link xmlns:xlink="http://www.w3.org/1999/xlink" ext-link-type="uri" xlink:href="http://doi.org/10.1601/nm.3093" xlink:type="simple">Escherichia coli</ext-link> </named-content> </italic> (EHEC) produces Shiga toxin 1 (Stx1) and Shiga toxin 2 (Stx2). Although <italic>stx1</italic> and <italic>stx2</italic> were found within the late operons of the Stx-encoding phages (Stx-phages), <italic>stx1</italic> could mainly be transcribed from the <italic>stx1</italic> promoter (<italic>P</italic> _Stx1), which represents the functional operator-binding site (Fur box) for the transcriptional regulator Fur (ferric uptake regulator), upstream of <italic>stx1</italic>. In this study, we found that the production of Stx1 by EHEC was affected by oxygen concentration. Increased Stx1 production in the presence of oxygen is dependent on Fur, which is an Fe²⁺-responsive transcription factor. The intracellular Fe²⁺ pool was lower under microaerobic conditions than under anaerobic conditions, suggesting that lower Fe²⁺ availability drove the formation of less Fe²⁺-Fur, less DNA binding to the <italic>P</italic> _Stx1 region, and an increase in Stx1 production.

Sub-MICs of the 14-membered macrolides erythromycin (EM) and clarithromycin (CAM) decreased the growth of Pseudomonas aeruginosa PAO1 and increased its sensitivity to endogenous and exogenous nitrosative stress. However, a 16-membered macrolide, josamycin (JM), was not or less effective. In 9 of 13 non-multidrug-resistant P. aeruginosa (non-MDRP) and 9 of 27 MDRP ST235 strains, the sub-MIC of EM induced significant reductions in bacterial numbers following treatment with a nitric oxide donor.