Open AccessHighly conserved B‐subunit genes of Shiga‐like toxin II variants found in Escherichia coli O157 strains
Author(s) -
Rüssmann Holger,
Schmidt Herbert,
Caprioli Alfredo,
Karch Helge
Publication year - 1994
Publication title -
fems microbiology letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.899
H-Index - 151
eISSN - 1574-6968
pISSN - 0378-1097
DOI - 10.1111/j.1574-6968.1994.tb06849.x
Subject(s) - biology , gene , escherichia coli , genetics , homology (biology) , nucleic acid sequence , shiga like toxin , toxin , sequence analysis , microbiology and biotechnology , shiga toxin
To determine the degree of heterogeneity among Shiga‐like toxin‐II (SLT‐II)‐related toxins present in enterohemorrhagic Escherichia coli O157 strains, slt‐IIB ‐related genes of 15 strains were amplified and sequenced. Of these 15 isolates, six contained only the slt‐II ‐related genes, seven strains harbored slt‐II ‐related genes together with slt‐II , and two strains had slt‐II ‐related genes plus slt‐I . In strains carruing slt‐II ‐related genes alone or in combination with slt‐I , the PCR fragments were directly subjected to Taq cycle sequence analysis. Direct sequencing was not possible with the seven strains possessing both slt‐II and slt‐II ‐related genes, since the PCR products contained both genes. In order to allow sequence analysis of these slt‐II ‐related genes, the PCR products were first subjected to restriction enzyme digestion with Fok I, which selectively digested slt‐IIB . This resulted in an undigested 270‐bp fragment consisting of pure slt‐II ‐related genes. Interestingly, comparison of the nucleotide sequences revealed 100% homology of all analyzed 15 slt‐IIB ‐related toxin genes. In addition, the nucleotide sequence of slt‐IIB ‐related toxin genes were identical to slt‐IIcB . Our findings indicate that SLT‐IIc is a major variant form of SLT‐II present in E. coli O517 strains.