title: Seasonal variation of Shiga toxin-encoding genes (stx) and detection of E. coli O157 in dairy cattle from Argentina.
abstract: OBJECTIVE
  To study the seasonal variation of Shiga toxin-encoding genes (stx) and to investigate the presence of Shiga toxin-producing Escherichia coli (STEC) O157 in cattle belonging to five dairy farms from Argentina.
  
  
  RESULTS
  Rectal swab samples were collected from 360 dairy cows in each season and 115 and 137 calves in autumn and in spring, respectively. The stx were investigated by multiplex PCR and it was used as the indicator for STEC. Samples positives for stx were tested by PCR for eae-gamma1 of E. coli O157 and then subjected to IMS (immunomagnetic separation). In positive animals significant differences in the prevalence of stx between warm and cold seasons were detected. In warm seasons, stx1 + stx2 increased and stx1 decreased, independently of the animal category. The prevalence of STEC O157 in cows and calves were 0.2% and 0.8%, respectively.
  
  
  CONCLUSIONS
  This work provides new data about the occurrence of stx and STEC O157 in dairy herds from Argentina and suggests a relationship between the type of stx and season of year.
  
  
  CONCLUSIONS
  The detection of STEC O157 and the seasonality of stx and its types provide an opportunity to improve control strategies designed to prevent contamination of food products and transmission animal-person.
authors.affiliation: Laboratorio de Inmunoquímica y Biotecnología, Tandil, Argentina.
authors.forename: D
authors.initials: D
authors.lastname: Fernández
authors.forename: E M
authors.initials: EM
authors.lastname: Rodríguez
authors.forename: G H
authors.initials: GH
authors.lastname: Arroyo
authors.forename: N L
authors.initials: NL
authors.lastname: Padola
authors.forename: A E
authors.initials: AE
authors.lastname: Parma
mesh_terms: D000818:Animals; D001118:Argentina / Q000453:epidemiology; D002417:Cattle / Q000382:microbiology; D004927:Escherichia coli Infections / Q000453:epidemiology* / Q000662:veterinary*; D019453:Escherichia coli O157 / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D015995:Prevalence; D012007:Rectum / Q000382:microbiology; D012621:Seasons; D022621:Shiga Toxin / Q000096:biosynthesis / Q000235:genetics*
chemical_list: D022621:Shiga Toxin