Unkmeir A, Schmidt H
Institut für Hygiene und Mikrobiologie der Universität Würzburg, D-97080 Würzburg, Germany.
Infect Immun. 2000 Sep;68(9):4856-64. doi: 10.1128/IAI.68.9.4856-4864.2000.
The stx-flanking regions of 49 Shiga toxin-producing Escherichia coli strains and nine Shigella dysenteriae serotype 1 strains containing either stx, stx(1), stx(2), or stx(2) variant genes, were examined. We analyzed these regions by PCR using a set of primers with one primer specific for the respective stx gene and a second primer complementary to sequences of Stx phages H-19B and 933W. We further characterized the amplification products by restriction endonuclease digestion and nucleotide sequencing. PCR products of stx(1)-containing E. coli strains of serogroups O157, O26, and 0103 showed the same lengths and similar restriction patterns. However, we failed to amplify the 3' stx-flanking region in stx(1)-harboring E. coli O111:H(-) strains. Stx2-producing E. coli strains revealed amplification products of different lengths and restriction patterns, suggesting greater heterogeneity than in stx(1)-positive strains. We also obtained specific PCR products for two Stx2c-producing and seven Stx2f-producing E. coli strains when they were subjected to PCR analysis. In nine S. dysenteriae type 1 strains, H-19B- and 933W-specific primers amplified only the 3' stx-flanking region. The results of our study demonstrate that the stx genes of all strains investigated are continuous with phage sequences. Whereas almost all strains except E. coli O111:H(-) strains were associated with a S-like gene, association with Q could not be demonstrated in nine S. dysenteriae type 1 strains and three E. coli strains. Furthermore, we showed that the organization of the stx-flanking regions is similar in all strains investigated, whereas fine-structure analysis showed subtle differences among the sequences examined. Our results support the hypothesis that stx genes in E. coli and S. dysenteriae are generally phage-borne.
对49株产志贺毒素大肠杆菌菌株和9株含有stx、stx(1)、stx(2)或stx(2)变异基因的痢疾志贺氏菌1型菌株的stx侧翼区域进行了检测。我们使用一组引物通过PCR分析这些区域，其中一个引物对各自的stx基因具有特异性，另一个引物与Stx噬菌体H-19B和933W的序列互补。我们通过限制性内切酶消化和核苷酸测序进一步对扩增产物进行了表征。血清型为O157、O26和O103的含stx(1)大肠杆菌菌株的PCR产物显示出相同的长度和相似的限制性图谱。然而，我们未能在携带stx(1)的大肠杆菌O111:H(-)菌株中扩增出3' stx侧翼区域。产Stx2的大肠杆菌菌株显示出不同长度和限制性图谱的扩增产物，表明其异质性高于stx(1)阳性菌株。当对两个产Stx2c和七个产Stx2f的大肠杆菌菌株进行PCR分析时，我们也获得了特异性的PCR产物。在9株痢疾志贺氏菌1型菌株中，H-19B和933W特异性引物仅扩增出3' stx侧翼区域。我们的研究结果表明，所有研究菌株的stx基因都与噬菌体序列相连。除大肠杆菌O111:H(-)菌株外，几乎所有菌株都与一个S样基因相关，但在9株痢疾志贺氏菌1型菌株和3株大肠杆菌菌株中未发现与Q基因相关。此外，我们表明，所有研究菌株中stx侧翼区域的组织相似，而精细结构分析显示所检测序列之间存在细微差异。我们的结果支持大肠杆菌和痢疾志贺氏菌中的stx基因通常由噬菌体携带的假说。
