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Activatable Shiga toxin 2d (Stx2d) in STEC strains isolated from cattle and sheep at slaughter.


Tasara, T; Bielaszewska, M; Nitzsche, S; Karch, H; Zweifel, C; Stephan, R (2008). Activatable Shiga toxin 2d (Stx2d) in STEC strains isolated from cattle and sheep at slaughter. Veterinary Microbiology, 131(1-2):199-204.

Abstract

Shiga toxin producing Escherichia coli (STEC) harbouring the stx2d-activatable gene and expressing the mucus- and elastase-activatable phenotype have been associated with severe outcomes of human disease. However, there is limited data available on the occurrence of such strains in livestock reservoirs. In this study, we analyzed 11 STEC strains isolated from healthy cattle and sheep at slaughter that were originally detected to contain the stx2c allele, for the presence of the stx2d-activatable genotype. Ten of the 11 strains displayed the stx2d-activatable genotype as determine by PstI restriction fragment length polymorphism (RFLP) of 890-bp fragments of their stx genes. However, only in six of 10 strains whose stx genes were sequenced, the presence of stx2d-activatable could be confirmed based on the predicted amino acid sequence of their StxA subunits; the remaining four strains contained Stx2c A subunit. Five of the six strains which contained stx2d-activatable displayed the activatable phenotype on Vero cells. Genes for adhesins such as the outer membrane protein intimin (eae), which is essential for the intimate attachment and the formation of attaching-and-effacing lesions on intestinal epithelial cells, or the STEC autoagglutinating adhesin (saa), potentially important in eae-negative STEC, were not detected. Moreover, all the strains tested negative for EHEC-hlyA encoding enterohaemorrhagic E. coli (EHEC) hemolysin.
To our knowledge, this is the first study that reports the presence of STEC harbouring stx2d-activatable and producing the activatable Stx2d in fecal samples of sheep. Therefore both cattle and sheep are reservoirs of such strains and potential sources of human infections. This is of particular importance, because in contrast to other eae-negative STEC, strains producing Stx2dactivatable may cause severe diseases such as bloody diarrhoea and haemolytic uremic syndrome in humans.

Shiga toxin producing Escherichia coli (STEC) harbouring the stx2d-activatable gene and expressing the mucus- and elastase-activatable phenotype have been associated with severe outcomes of human disease. However, there is limited data available on the occurrence of such strains in livestock reservoirs. In this study, we analyzed 11 STEC strains isolated from healthy cattle and sheep at slaughter that were originally detected to contain the stx2c allele, for the presence of the stx2d-activatable genotype. Ten of the 11 strains displayed the stx2d-activatable genotype as determine by PstI restriction fragment length polymorphism (RFLP) of 890-bp fragments of their stx genes. However, only in six of 10 strains whose stx genes were sequenced, the presence of stx2d-activatable could be confirmed based on the predicted amino acid sequence of their StxA subunits; the remaining four strains contained Stx2c A subunit. Five of the six strains which contained stx2d-activatable displayed the activatable phenotype on Vero cells. Genes for adhesins such as the outer membrane protein intimin (eae), which is essential for the intimate attachment and the formation of attaching-and-effacing lesions on intestinal epithelial cells, or the STEC autoagglutinating adhesin (saa), potentially important in eae-negative STEC, were not detected. Moreover, all the strains tested negative for EHEC-hlyA encoding enterohaemorrhagic E. coli (EHEC) hemolysin.
To our knowledge, this is the first study that reports the presence of STEC harbouring stx2d-activatable and producing the activatable Stx2d in fecal samples of sheep. Therefore both cattle and sheep are reservoirs of such strains and potential sources of human infections. This is of particular importance, because in contrast to other eae-negative STEC, strains producing Stx2dactivatable may cause severe diseases such as bloody diarrhoea and haemolytic uremic syndrome in humans.

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Additional indexing

Item Type:Journal Article, refereed, original work
Communities & Collections:05 Vetsuisse Faculty > Institute of Food Safety and Hygiene
Dewey Decimal Classification:570 Life sciences; biology
610 Medicine & health
Uncontrolled Keywords:Shiga toxin producing Escherichia coli; stx2d-activatable; Mucus activation assay; Livestock
Language:English
Date:2008
Deposited On:18 Nov 2008 11:01
Last Modified:05 Apr 2016 12:33
Publisher:Elsevier
ISSN:0378-1135
Publisher DOI:10.1016/j.vetmic.2008.03.001
Permanent URL: http://doi.org/10.5167/uzh-5114

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