| 1. |
- Johura, Fatema-Tuz, et al.
(författare)
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Occurrence of Hybrid Escherichia coli Strains Carrying Shiga Toxin and Heat-Stable Toxin in Livestock of Bangladesh
- 2017
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Ingår i: Frontiers In Public Health. - : Frontiers Media SA. - 2296-2565. ; 4
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Tidskriftsartikel (refereegranskat)abstract
- Shiga toxin-producing Escherichia coli (STEC) and enterotoxigenic E. coli (ETEC) are important causes of diarrhea in humans and animals worldwide. Although ruminant animals are the main source of STEC, diarrhea due to this pathotype is very low in Bangladesh where ETEC remains the predominant group associated with childhood diarrhea. In the present study, E. coli strains (n = 35) isolated from Bangladesh livestock (goats, sheep, and cattle) and poultry (chicken and ducks) were analyzed for the presence of major virulence factors, such as Shiga toxins (STX-1 and STX-2), heat-labile toxin, and heat-stable toxins (STa and STb). Multiplex polymerase chain reaction results revealed 23 (66%) E. coli strains to be virulent possessing either sta (n = 5), stx (stx1, n = 8; stx2, n = 2), or both (n = 8) genes in varying combinations. Thirty-four percent (8/23) of strains from livestock were hybrid type that carried both stx (either stx1 or stx2) and ETEC-specific enterotoxin gene sta. Serotyping results revealed that the ETEC strains belonged to five serotypes, namely O36: H5, O174: H-, O152: H8, O109: H51, and O8: H21, while the STEC-producing strains belonged to serotypes O76: H19 (n = 3), O43: H2 (n = 2), O87: H16 (n = 2), OR: H2 (n = 1), O110: H16 (n = 1), and O152: H8 (n = 1). The STEC-ETEC hybrid strains belonged to serotypes O76: H19 (n = 3), O43: H2 (n = 2), O87: H16, OR: H2, and O152: H8. Forty percent (2/5) of the ETEC and 20% (2/10) of the STEC strains were multidrug resistant with the highest drug resistance (50%) being found in the hybrid strains. Molecular fingerprinting determined by pulsed-field gel electrophoresis and cluster analyses by dendrogram revealed that, genetically, STEC-ETEC hybrid strains were highly heterogeneous. Multidrug-resistant E. coli STEC-ETEC hybrid strains in domesticated animals pose a public health threat for humans in Bangladesh.
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| 3. |
- Yamamoto, Shouji, et al.
(författare)
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Regulation of natural competence by the orphan two-component system sensor kinase ChiS involves a non-canonical transmembrane regulator in Vibrio cholerae
- 2014
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Ingår i: Molecular Microbiology. - : John Wiley & Sons. - 0950-382X .- 1365-2958. ; 91:2, s. 326-347
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Tidskriftsartikel (refereegranskat)abstract
- In Vibrio cholerae, 41 chitin-inducible genes, including the genes involved in natural competence for DNA uptake, are governed by the orphan two-component system (TCS) sensor kinase ChiS. However, the mechanism by which ChiS controls the expression of these genes is currently unknown. Here, we report the involvement of a novel transcription factor termed TfoS' in this process. TfoS is a transmembrane protein that contains a large periplasmic domain and a cytoplasmic AraC-type DNA-binding domain, but lacks TCS signature domains. Inactivation of tfoS abolished natural competence as well as transcription of the tfoR gene encoding a chitin-induced small RNA essential for competence gene expression. A TfoS fragment containing the DNA-binding domain specifically bound to and activated transcription from the tfoR promoter. Intracellular TfoS levels were unaffected by disruption of chiS and coexpression of TfoS and ChiS in Escherichia coli recovered transcription of the chromosomally integrated tfoR::lacZ gene, suggesting that TfoS is post-translationally modulated by ChiS during transcriptional activation; however, this regulation persisted when the canonical phosphorelay residues of ChiS were mutated. The results presented here suggest that ChiS operates a chitin-induced non-canonical signal transduction cascade through TfoS, leading to transcriptional activation of tfoR.
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