Regulatory elements of stx2 gene and the expression level of Shiga-like toxin 2 in Escherichia coli O157:H7.
OBJECTIVE
Shiga-like toxin (Stx) is an important factor in the pathogenesis of Escherichia coli O157:H7 infection and is responsible for some severe complications. Stx2 is usually associated with hemolytic uremic syndrome in humans. Its expression is regulated by elements located upstream of the stx2 gene, including stx2-promoter sequence, ribosome binding site, and the antiterminator q gene. The present study aimed to find the correlation between regulatory elements and the expression level of Stx2 in two local isolates of E. coli O157:H7.


METHODS
Two local E. coli O157:H7 strains SM-25(1) and KL-48(2), originating from human and cattle feces, respectively, and an E. coli reference strain, ATCC 43894, were investigated. The complete stx2 gene covering the sequences of promoter, ribosome binding site, and open reading frame and q gene of each strain was analyzed. The magnitude of Stx2 production was detected with a reverse passive latex agglutination method and Stx mediated cellular damage was determined with the Vero cell assay.


RESULTS
A comparison of the complete stx2 gene contained stx2-promoter, ribosome binding site, and q genes of two local strains KL-48(2) and SM25(1), and the E. coli ATCC 43894 showed that the amino acid sequences were identical. Both local isolates were Stx negative in the reverse passive latex agglutination test and nontoxic in the Vero cell assay.


CONCLUSIONS
The expression level of Shiga-like toxin of the two local isolates of E. coli O157:H7 did not only depend on the regulatory elements of the stx2 gene.
Department of Veterinary Public Health, Faculty of Veterinary Medicine, Udayana University, Denpasar, Indonesia. Electronic address: iwayansuardana22@yahoo.com.
I Wayan
IW
Suardana
Department of Microbiology, Faculty of Medicine, Udayana University, Denpasar, Indonesia.
Komang Januartha Putra
KJP
Pinatih
Department of Veterinary Public Health, Faculty of Veterinary Medicine, Gadjah Mada University, Karang Malang, Yogyakarta, Indonesia.
Dyah Ayu
DA
Widiasih
Department of Biochemistry, Faculty of Veterinary Medicine, Gadjah Mada University, Karang Malang, Yogyakarta, Indonesia.
Wayan Tunas
WT
Artama
Department of Microbiology, Faculty of Veterinary Medicine, Gadjah Mada University, Karang Malang, Yogyakarta, Indonesia.
Widya
W
Asmara
Department of Genetic, Faculty of Biology, Gadjah Mada University, Sekip Utara, Yogyakarta, Indonesia.
Budi Setiadi
BS
Daryono
D000818:Animals; D001483:Base Sequence; D001665:Binding Sites; D002417:Cattle; D002448:Cell Adhesion; D002470:Cell Survival; D002522:Chlorocebus aethiops; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D004927:Escherichia coli Infections / Q000382:microbiology; D019453:Escherichia coli O157 / Q000235:genetics* / Q000378:metabolism* / Q000472:pathogenicity; D005243:Feces / Q000382:microbiology; D015964:Gene Expression Regulation, Bacterial / Q000235:genetics*; D016341:Genes, vif / Q000235:genetics; D006801:Humans; D010802:Phylogeny; D011401:Promoter Regions, Genetic; D016415:Sequence Alignment; D017421:Sequence Analysis; D022641:Shiga Toxin 2 / Q000096:biosynthesis / Q000145:classification / Q000235:genetics*; D014709:Vero Cells
D004269:DNA, Bacterial; D022641:Shiga Toxin 2; C430449:verocytotoxin 2
Escherichia coli O157:H7; Shiga-like toxin titer; promoter; q gene; ribosome binding site