Characterization of a Shiga-Like Toxin Converting Phage Isolated from an Escherichia coli Strain Responsible for Hemorrhagic Colitis in Humans

摘要

There is a strong correlation between the ability of Escherichia coli to produce high levels of Shiga-like toxin in vitro and to cause hemorrhagic colitis in humans. A Shiga-like toxin-converting phage from Escherichia coli 0157:H7 strain 933 (phage 933J) and another Shiga-like toxin-converting phage from Escherichia coli 026 strain H-19 (phage H=19J) were isolated and found to be closely related by morphology, virion polypeptide composition, pattern of DNA restriction fragments, heat stability, and lysogenic immunity. However, a difference was noted between phage 933J and H-19J in the range of bacterial hosts on which these phages would plaque. The phage 933J toxin-converting genes were cloned into pBR328 and expressed in Escherichia coli HB101. DNA restriction mapping, subcloning, and examination of the cloned gene products by minicell analysis were used to localize the toxin-converting genes and identify them as the structural genes for Shiga-like toxin. Southern hybridization studies demonstrated that the DNA fragment containing the cloned toxin structural genes was homologous with the chromosomes of Shigella. (Author)