Verotoxigenic <it>Escherichia coli </it>O157:H7 from Swedish cattle; isolates from prevalence studies versus strains linked to human infections - A retrospective study

• Main Authors: Eriksson Erik, Aspán Anna
• Format: Article
• Language: English
• Published: BMC 2010-01-01
• Series: BMC Veterinary Research
• Online Access: http://www.biomedcentral.com/1746-6148/6/7

<p>Abstract</p> <p>Background</p> <p>Several cases of human infection caused by verotoxin-producing <it>Escherichia coli </it>(VTEC) O157:H7 in Sweden have been connected with cattle farm visits. Between 1996 and 2002, 18 farms were classified as the source of human cases with isolation of EHEC (Enterohaemorrhagic <it>Escherichia coli</it>) after VTEC O157:H7 had been isolated from cattle on those farms.</p> <p>Results</p> <p>Characterization by phage typing and molecular methods of the strains isolated from these 18 farms, including PCR for virulence genes (<it>vtx</it>₁, <it>vtx</it>₂and variants thereof, <it>eaeA </it>and EHEC-<it>hlyA</it>) and Pulsed-Field Gel Electrophoresis (PFGE), demonstrated a cluster of very similar strains from 16 farms. All were of phage type 4, carried the genes encoding the verotoxins VT2 and VT2c, intimin, EHEC-haemolysin and flagellin H7 as shown by PCR, and had identical or very similar PFGE patterns. When analysing strains in a prevalence study of VTEC O157:H7 from cattle at slaughter as well as from an on-farm prevalence study of dairy cattle, using the same typing methods, a rather wide variation was observed among the isolated VTEC O157:H7 strains.</p> <p>Conclusions</p> <p>In Sweden, a limited group of genetically similar and highly pathogenic VTEC O157:H7 strains seem to predominate in direct or indirect transmission from cattle to man.</p>