Two entomopathogenic bacteria, Xenorhabdus nematophila (Xn) and Photorhabdus temperata temperata (Ptt), maintain monoxenic condition within host insect cadaver by synthesizing and releasing various antibiotics. These two bacteria were cultured in tryptic soy broth during different times, which were screened in their antibacterial activities. Both bacterial culture broth had high antibacterial activities against Escherichia coli at their stationary growth phase. The potent culture broth was used to screen target plant bacterial pathogens using both inhibition zone assay and liquid culture assay. Ralstonia sp. was most susceptible, while Xanthomonas sp. was highly resistant. Pseudomonas sp. and Bacillus sp. showed hemi-susceptible. The culture broth was further fractionated into hexane and diethylether extracts. Significant antibacterial effect was found in the diethylether extract