Open AccessGenomic Variability of O Islands Encoding Tellurite Resistance in Enterohemorrhagic Escherichia coli O157:H7 Isolates
Author(s) -
Diane E. Taylor,
Michelle M. Rooker,
M. Keelan,
Lai-King Ng,
Irene Freire Martín,
Nicole T. Perna,
N. T. Valerie Burland,
Fredrick R. Blattner
Publication year - 2002
Publication title -
journal of bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.652
H-Index - 246
eISSN - 1067-8832
pISSN - 0021-9193
DOI - 10.1128/jb.184.17.4690-4698.2002
Subject(s) - biology , escherichia coli , stx2 , microbiology and biotechnology , gene , strain (injury) , enterobacteriaceae , bacteria , genetics , shiga toxin , anatomy
Strains ofEscherichia coli causing enterohemorrhagic colitis belonging to the O157:H7 lineage are reported to be highly related. Fifteen strains ofE. coli O157:H7 and 1 strain ofE. coli O46:H− (nonflagellated) were examined for the presence of potassium tellurite resistance (Ter ). Ter genes comprisingterABCDEF were shown previously to be part of a pathogenicity island also containing integrase, phage, and urease genes. PCR analysis, both conventional and light cycler based, demonstrated that about one-half of the Ter E. coli O157:H7 strains (6 of 15), including the Sakai strain, which has been sequenced, carried a single copy of the Ter genes. Five of the strains, including EDL933, which has also been sequenced, contained two copies. Three other O157:H7 strains and the O46:H− strain did not contain the Ter genes. In strains containing two copies, the Ter genes were associated with theserW andserX tRNA genes. Five O157:H7 strains resembled the O157 Sakai strain whose sequence contained one copy, close toserX , whereas in one isolate the single copy was associated withserW . There was no correlation between Ter and the ability to produce Shiga toxin ST1 or ST2. The Ter MIC for most strains, containing either one or two copies, was 1,024 μg/ml, although for a few the MIC was intermediate, 64 to 128 μg/ml, which could be increased to 512 μg/ml by pregrowth of strains in subinhibitory concentrations of potassium tellurite. Reverse transcriptase PCR analysis confirmed that in most strains Ter was constitutive but that in the rest it was inducible and involved induction ofterB andterC genes. Only theterB , -C , -D , and -E genes are required for Ter . The considerable degree of homology between theter genes on IncH12 plasmid R478, which originated inSerratia marcescens , and pTE53, from anE. coli clinical isolate, suggests that the pathogenicity island was acquired from a plasmid. This work demonstrates diversity amongE. coli O157:H7 isolates, at least as far as the presence of Ter genes is concerned.