title: Selected lactic acid-producing bacterial isolates with the capacity to reduce Salmonella translocation and virulence gene expression in chickens.
abstract: BACKGROUND
  Probiotics have been used to control Salmonella colonization/infection in chickens. Yet the mechanisms of probiotic effects are not fully understood. This study has characterized our previously-selected lactic acid-producing bacterial (LAB) isolates for controlling Salmonella infection in chickens, particularly the mechanism underlying the control.
  
  
  RESULTS
  In vitro studies were conducted to characterize 14 LAB isolates for their tolerance to low pH (2.0) and high bile salt (0.3-1.5%) and susceptibility to antibiotics. Three chicken infection trials were subsequently carried out to evaluate four of the isolates for reducing the burden of Salmonella enterica serovar Typhimurium in the broiler cecum. Chicks were gavaged with LAB cultures (10(6-7) CFU/chick) or phosphate-buffered saline (PBS) at 1 day of age followed by Salmonella challenge (10(4) CFU/chick) next day. Samples of cecal digesta, spleen, and liver were examined for Salmonella counts on days 1, 3, or 4 post-challenge. Salmonella in the cecum from Trial 3 was also assessed for the expression of ten virulence genes located in its pathogenicity island-1 (SPI-1). These genes play a role in Salmonella intestinal invasion. Tested LAB isolates (individuals or mixed cultures) were unable to lower Salmonella burden in the chicken cecum, but able to attenuate Salmonella infection in the spleen and liver. The LAB treatments also reduced almost all SPI-1 virulence gene expression (9 out of 10) in the chicken cecum, particularly at the low dose. In vitro treatment with the extracellular culture fluid from a LAB culture also down-regulated most SPI-1 virulence gene expression.
  
  
  CONCLUSIONS
  The possible correlation between attenuation of Salmonella infection in the chicken spleen and liver and reduction of Salmonella SPI-1 virulence gene expression in the chicken cecum by LAB isolates is a new observation. Suppression of Salmonella virulence gene expression in vivo can be one of the strategies for controlling Salmonella infection in chickens.
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Xiaojian
authors.initials: X
authors.lastname: Yang
authors.affiliation: Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Brisbin
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Hai
authors.initials: H
authors.lastname: Yu
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Qi
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Fugui
authors.initials: F
authors.lastname: Yin
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Yonggang
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Parviz
authors.initials: P
authors.lastname: Sabour
authors.affiliation: Department of Pathobiology, University of Guelph, Guelph, Ontario, Canada.
authors.forename: Shayan
authors.initials: S
authors.lastname: Sharif
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Joshua
authors.initials: J
authors.lastname: Gong
mesh_terms: D000818:Animals; D002645:Chickens; D019344:Lactic Acid; D008099:Liver / Q000382:microbiology; D019936:Probiotics / Q000627:therapeutic use*; D012475:Salmonella / Q000472:pathogenicity*; D012480:Salmonella Infections / Q000188:drug therapy / Q000382:microbiology; D013154:Spleen / Q000382:microbiology; D014774:Virulence / Q000502:physiology*
chemical_list: D019344:Lactic Acid
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