Aims: To identify a fast, economic and reliable method for preselecting lactic acid-producing bacterial (LAB) isolates to control enterotoxigenic Escherichia coli (ETEC). Methods and Results: Two assays with porcine intestinal epithelial IPEC-J2 cells or Caenorhabditis elegans for selecting effective probiotic candidates were compared. Both assays were based on measuring death of cells or worms caused by ETEC strain JG280. Six of 13 LAB isolates showed >= 50% protection in each assay, among which only four isolates (>= 50% protection) were consistently selected by both assays. Isolate CL9 (Lactobacillus reuteri) was further studied. It reduced gene expression of estA, estB and elt in JG280 in both assays. Furthermore, the isolate protected IPEC-J2 and C. elegans from cell and worm death caused by STa, STb or LT enterotoxin expressed in E. coli DH5 alpha. CL9 also promoted host defensive responses by decreasing IL-8 and increasing IL-10 production in IPEC-J2 cells and expression of antimicrobial peptide genes clec-60, clec-85 in C. elegans. Conclusions: Caenorhabditis elegans is useful for preselecting probiotic candidates to control ETEC after initial screening with IPEC-J2 cells. Significance and Impact of the Study: A combination of IPEC-J2 cell and C. elegans assays can improve the effectiveness in preselecting probiotic candidates.