title: Lactobacillus zeae protects Caenorhabditis elegans from enterotoxigenic Escherichia coli-caused death by inhibiting enterotoxin gene expression of the pathogen.
abstract: BACKGROUND
  The nematode Caenorhabditis elegans has become increasingly used for screening antimicrobials and probiotics for pathogen control. It also provides a useful tool for studying microbe-host interactions. This study has established a C. elegans life-span assay to preselect probiotic bacteria for controlling K88(+) enterotoxigenic Escherichia coli (ETEC), a pathogen causing pig diarrhea, and has determined a potential mechanism underlying the protection provided by Lactobacillus.
  
  
  RESULTS
  Life-span of C. elegans was used to measure the response of worms to ETEC infection and protection provided by lactic acid-producing bacteria (LAB). Among 13 LAB isolates that varied in their ability to protect C. elegans from death induced by ETEC strain JG280, Lactobacillus zeae LB1 offered the highest level of protection (86%). The treatment with Lactobacillus did not reduce ETEC JG280 colonization in the nematode intestine. Feeding E. coli strain JFF4 (K88(+) but lacking enterotoxin genes of estA, estB, and elt) did not cause death of worms. There was a significant increase in gene expression of estA, estB, and elt during ETEC JG280 infection, which was remarkably inhibited by isolate LB1. The clone with either estA or estB expressed in E. coli DH5α was as effective as ETEC JG280 in killing the nematode. However, the elt clone killed only approximately 40% of worms. The killing by the clones could also be prevented by isolate LB1. The same isolate only partially inhibited the gene expression of enterotoxins in both ETEC JG280 and E. coli DH5α in-vitro.
  
  
  CONCLUSIONS
  The established life-span assay can be used for studies of probiotics to control ETEC (for effective selection and mechanistic studies). Heat-stable enterotoxins appeared to be the main factors responsible for the death of C. elegans. Inhibition of ETEC enterotoxin production, rather than interference of its intestinal colonization, appears to be the mechanism of protection offered by Lactobacillus.
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China ; Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Mengzhou
authors.initials: M
authors.lastname: Zhou
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: Xianhua
authors.initials: X
authors.lastname: Yin
authors.affiliation: Guelph Food Research Centre, Agriculture and Agri-Food Canada, Guelph, Ontario, Canada.
authors.forename: Parviz M
authors.initials: PM
authors.lastname: Sabour
authors.affiliation: State Key Laboratory of Food Science and Technology, Jiangnan University, Wuxi, Jiangsu, China.
authors.forename: Wei
authors.initials: W
authors.lastname: Chen
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: D000704:Analysis of Variance; D000818:Animals; D017173:Caenorhabditis elegans / Q000235:genetics* / Q000382:microbiology* / Q000648:ultrastructure; D003001:Cloning, Molecular; D054307:Enterotoxigenic Escherichia coli / Q000378:metabolism*; D004768:Enterotoxins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000502:physiology*; D007422:Intestines / Q000382:microbiology; D007778:Lactobacillus / Q000502:physiology*; D046529:Microscopy, Electron, Transmission; D019936:Probiotics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013045:Species Specificity; D016019:Survival Analysis
chemical_list: D004768:Enterotoxins