Relationship between stx genotype and Stx2 expression level in Shiga toxin-producing Escherichia coli O157 strains.
To determine the expression level of Shiga toxin (Stx) 2-related toxins (Stx2 and Stx2c)  produced by each of 33 Stx-producing Escherichia coli (STEC) O157 strains, stx2 and stx2c mRNAs  (stx2-related mRNA) were measured using real-time PCR with primers that recognize sequences common to  stx2 and stx2c. The amount of Stx2 and Stx2c protein was measured using a reversed passive latex  agglutination (RPLA) kit. Expression of stx2-related mRNA was significantly higher in STEC O157  strains carrying the stx2 gene (i.e., stx2, stx1/stx2, or stx2/stx2c) than in most strains that  carried the stx2c gene but not the stx2 gene (i.e., stx2c or stx1/stx2c). RPLA might not measure the  precise amount of each toxin variant; nevertheless, stx2-inclusive strains had 40-fold higher mean  toxin titers than did strains that carried the stx2c gene but not the stx2 gene, with the exception of  1 stx2c strain. Interestingly, 1 stx2c strain that was isolated from a patient with severe hemorrhagic  diarrhea had the highest stx2-related mRNA expression and the highest toxin titer of all 33 STEC O157  strains. Taken together, these findings indicated that measurement of stx2-related mRNA expression  could reflect differences in production levels of toxins among STEC strains.
Miyazaki Prefectural Institute for Public Health and Environment, Miyazaki, Japan.
Kimiko
K
Kawano
Hidetoshi
H
Ono
Osamu
O
Iwashita
Mai
M
Kurogi
Takeshi
T
Haga
Ken
K
Maeda
Yoshitaka
Y
Goto
D019453:Escherichia coli O157 / Q000235:genetics* / Q000302:isolation & purification / Q000378:metabolism; D015964:Gene Expression Regulation, Bacterial; D005838:Genotype; D022641:Shiga Toxin 2 / Q000096:biosynthesis / Q000235:genetics*; D014158:Transcription, Genetic
D022641:Shiga Toxin 2