Evaluation of the Anti-Terminator Q933 Gene as a Marker for Escherichia coli O157:H7 with High Shiga Toxin Production

Ahmad, Aqeel; Zurek, Ludek

doi:10.1007/s00284-006-0089-3

Cited by 29 publications

(25 citation statements)

References 17 publications

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“…Previous studies have determined that Stx2 enhances E. coli O157:H7 colonization of cattle intestinal tissues (50) and that E. coli O157:H7 strains harboring the Q 933 variant of the antiterminator gene produced significantly higher levels of Shiga toxin 2 than strains with the Q 21 variant or strains harboring both Q 933 and Q 21 (26,49,51). The current results indicate that Q 933 does not impact supershedding, implying that increased Stx2 expression also does not affect supershedding.…”

Section: Resultssupporting

confidence: 44%

Characterization of Escherichia coli O157:H7 Strains Isolated from Supershedding Cattle

Arthur

Ahmed

Chase-Topping

et al. 2013

Appl Environ Microbiol

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Previous reports have indicated that a small proportion of cattle shedding high levels of Escherichia coli O157:H7 is the main source for transmission of this organism between animals. Cattle achieving a fecal shedding status of 10 4 CFU of E. coli O157: H7/gram or greater are now referred to as supershedders. The aim of this study was to investigate the contribution of E. coli O157:H7 strain type to supershedding and to determine if supershedding was restricted to a specific set of E. coli O157:H7 strains. Fecal swabs (n ‫؍‬ 5,086) were collected from cattle at feedlots or during harvest. Supershedders constituted 2.0% of the bovine population tested. Supershedder isolates were characterized by pulsed-field gel electrophoresis (PFGE), phage typing, lineage-specific polymorphism assay (LSPA), Stx-associated bacteriophage insertion (SBI) site determination, and variant analysis of Shiga toxin, tir, and antiterminator Q genes. Isolates representing 52 unique PFGE patterns, 19 phage types, and 12 SBI clusters were obtained from supershedding cattle, indicating that there is no clustering to E. coli O157:H7 genotypes responsible for supershedding. While being isolated directly from cattle, this strain set tended to have higher frequencies of traits associated with human clinical isolates than previously collected bovine isolates with respect to lineage and tir allele, but not for SBI cluster and Q type. We conclude that no exclusive genotype was identified that was common to all supershedder isolates. E scherichia coli O157:H7 is an important food-borne pathogen that poses a serious public health concern and financial burden. Cattle are the principal animal reservoir of E. coli O157:H7, and while the rumen has been shown to harbor this pathogen on occasion, it is found more frequently in the distal portion of the bovine gastrointestinal (GI) tract, with the rectoanal junction (RAJ) identified as the predominant colonization site (1, 2). Once colonized, an animal can shed various concentrations of E. coli O157:H7 organisms in the feces. Among colonized individuals, a small proportion will excrete E. coli O157:H7 at levels of Ն10 4 CFU/g of feces. These animals have been referred to as supershedders and are reported to be responsible for increased transmission of E. coli O157:H7 within cattle production environments as well as having significant effects on contamination of the cattle hide and carcass (3-6).Matthews et al. (7) presented data suggesting that 20% of the E. coli O157:H7 infections in cattle on Scottish farms were responsible for 80% of the transmission of the organism between animals. Another study showed that 9% of the animals shedding E. coli O157:H7 at harvest produced over 96% of the total E. coli O157:H7 fecal load for the group (6). Conversely, feedlot cattle that did not shed E. coli O157:H7 over the course of study were five times more likely to be housed in a pen that did not contain a supershedder (8). In addition, Arthur et al. (3) have shown that 95% of feedlot pens containing at least one sup...

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Section: Resultssupporting

confidence: 44%

Characterization of Escherichia coli O157:H7 Strains Isolated from Supershedding Cattle

Arthur

Ahmed

Chase-Topping

et al. 2013

Appl Environ Microbiol

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“…Within the LSPA-6 region, a 9-bp sequence (AGTGTATGA) is tandemly repeated (TR) once in lineage I and lineage I/II strains (TR 2 ), three times in lineage II strains FRIK2000 and FRIK966 (LSPA-2; TR 4 ), and twice in strain EC869 (TR 3 ). TR 3 , found in EC869, is thus termed LSPA-6-2b. Strains are further distinguished by a length polymorphism within the LSPA-1 locus.…”

Section: Resultsmentioning

confidence: 99%

“…Shiga toxin (stx)-converting phages of toxin subtypes stx 2 and stx 2c are more frequently carried in clinical STEC isolates, while stx 1 is more frequent in O157 and non-O157 STEC isolates of bovine origin (13, 32) (Eppinger, Mammel, LeClerc, Cebula, and Ravel, unpublished). Lineages I, I/II, and II are further distinguished by polymorphisms in toxin production and expression of other synergistic key virulence factors (3,10). STEC strains produce characteristic attaching and effacing (A/E) lesions mediated by the pathogenicity locus of enterocyte effacement (LEE) (57).…”

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confidence: 99%

Genome Signatures of Escherichia coli O157:H7 Isolates from the Bovine Host Reservoir

Eppinger

Mammel

LeClerc

et al. 2011

Appl Environ Microbiol

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Cattle comprise a main reservoir of Shiga toxin-producing Escherichia coli O157:H7 (STEC). The significant differences in host prevalence, transmissibility, and virulence phenotypes among strains from bovine and human sources are of major interest to the public health community and livestock industry. Genomic analysis revealed divergence into three lineages: lineage I and lineage I/II strains are commonly associated with human disease, while lineage II strains are overrepresented in the asymptomatic bovine host reservoir. Growing evidence suggests that genotypic differences between these lineages, such as polymorphisms in Shiga toxin subtypes and synergistically acting virulence factors, are correlated with phenotypic differences in virulence, host ecology, and epidemiology. To assess the genomic plasticity on a genome-wide scale, we have sequenced the whole genome of strain EC869, a bovine-associated E. coli O157:H7 isolate. Comparative phylogenomic analysis of this key isolate enabled us to place accurately bovine lineage II strains within the genetically homogenous E. coli O157:H7 clade. Identification of polymorphic loci that are anchored both in the chromosomal backbone and horizontally acquired regions allowed us to associate bovine genotypes with altered virulence phenotypes and host prevalence. This study catalogued numerous novel lineage II-specific genome signatures, some of which appear to be associated intimately with the altered pathogenic potential and niche adaptation within the bovine rumen. The presented extended list of polymorphic markers is valuable in the development of a robust typing system critical for forensic, diagnostic, and epidemiological studies of this emerging human pathogen.Shiga toxin-producing, non-sorbitol-fermenting, and ␤-glucuronidase-negative Escherichia coli (STEC) O157:H7 has evolved from an O55:H7-like progenitor (24, 50, 65) into an emerging human pathogen, with cattle as the main asymptomatic reservoir (12, 54). E. coli O157:H7 is transmitted from cattle to human by means of contaminated food products, such as undercooked meat, unpasteurized milk, fruit and vegetables, or tainted water. As seasonal changes can influence the prevalence and load of E. coli O157:H7 in cattle and super shedders exist within the bovine population (30,33,39,49,67), physical contact of humans with cattle and their environment introduces added risk of E. coli infection (29). Human infection manifests in various ways, ranging from mild to more severe bloody diarrhea. In some cases, infection can lead to renal dysfunction, i.e., hemolytic uremic syndrome (HUS), and central nervous system (CNS) failure (10,17,73). Epidemiological data have demonstrated a high prevalence of E. coli O157:H7 in cattle and their environment but a comparatively low incidence of human infection. This supports the notion that a subset of STEC O157:H7 strains harbored in cattle causes the majority of human disease (18). Genetic heterogeneity among STEC O157:H7 strains has been established using a broad panel of typing m...

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“…The bacteriophage antiterminator gene alleles (Q 933 and Q 21 ) were detected by PCR using the Applied Biosystems GeneAmp 9700 thermal cycler with the primer sequences and cycling conditions described by Ahmad & Zurek (2006) (Table S1). …”

Section: Methodsmentioning

confidence: 99%

“…Shiga toxin bacteriophage insertion (SBI) site analysis relies on amplification of the stx toxin genes (stx 1 and stx 2 ) and the insertion site junctions of their encoding bacteriophages that can be used as a valuable genotyping technique to distinguish E. coli O157 : H7 strains, based on their distribution, gene expression and virulence potential (Besser et al, 2008;Shaikh & Tarr, 2003). Moreover, Shiga toxin 2 variants (stx 2a and stx 2c ) and stx 2 -Q antiterminator gene variants are clinically relevant genetic markers among E. coli O157 : H7 (Ahmad & Zurek, 2006;Persson et al, 2007).…”

Section: Introductionmentioning

confidence: 99%

Genetic diversity of Shiga toxin-producing Escherichia coli O157 : H7 recovered from human and food sources

et al. 2015

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The aim of this study was to identify an epidemiological association between Shiga toxinproducing Escherichia coli O157 : H7 strains associated with human infection and with food sources. Frequency distributions of different genetic markers of E. coli O157 : H7 strains recovered from human and food sources were compared using molecular assays to identify E. coli O157 : H7 genotypes associated with variation in pathogenic potential and host specificity. Genotypic characterization included: lineage-specific polymorphism assay (LSPA-6), clade typing, tir (A255T) polymorphism, Shiga toxin-encoding bacteriophage insertion site analysis and variant analysis of Shiga toxin 2 gene (stx 2a and stx 2c ) and antiterminator Q genes (Q 933 and Q 21 ). The intermediate lineage (LI/II) dominated among both food and human strains. Compared to other clades, clades 7 and 8 were more frequent among food and human strains, respectively. The tir (255T) polymorphism occurred more frequently among human strains than food strains. Q 21 and Q 933+Q21 were found at significantly higher frequencies among food and human strains, respectively. Moreover, stx 2a and stx 2a+c were detected at significantly higher frequencies among human strains compared to food strains. Bivariate analysis revealed significant concordance (P,0.05) between the LSPA-6 assay and the other typing methods. Multivariable regression Abbreviations: HP, hairpin; HUS, haemolytic uraemic syndrome; LSPA-6, lineage-specific polymorphism assay; SBI, Shiga toxin bacteriophage insertion; STEC, Shiga toxin-producing Escherichia coli; stx 1 , Shiga toxin 1; stx 2 , Shiga toxin 2.Five supplementary tables are available with the online Supplementary Material.

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Evaluation of the Anti-Terminator Q933 Gene as a Marker for Escherichia coli O157:H7 with High Shiga Toxin Production

Cited by 29 publications

References 17 publications

Characterization of Escherichia coli O157:H7 Strains Isolated from Supershedding Cattle

Characterization of Escherichia coli O157:H7 Strains Isolated from Supershedding Cattle

Genome Signatures of Escherichia coli O157:H7 Isolates from the Bovine Host Reservoir

Genetic diversity of Shiga toxin-producing Escherichia coli O157 : H7 recovered from human and food sources

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