Environmental effects on the production of Shiga-like toxins byEscherichia coli 0157:H7 as revealed by sandwiched immuno-chemiluminescence detection

摘要

We have developed a sandwiched immuno assay to detect sensitively Shiga-like toxins (SLTs) produced by Escherichia coli 0157:H7. The method involved the capture of toxins by specific immuno magnetic beads followed by tagging the toxins with peroxidase-labeled anti E. coli 0157:H7 antibody. Upon addition of proper substrate, peroxidase induced luminescence was used to measure the presence of SLTs. We have previously demonstrated that co-incubation'of shiga toxin (SLT) producing E. coli 0157:H7 with certain other bacteria can inhibit toxin production but does not affect the growth of the E. coli. We show here that media in which the cells have grown been centrifuged from (conditioned media) have similar effects on cell growth and SLT production. Adjusting the pH and adding nutrients to the conditioned media did not have any effect on the reduction of SLT produced. Bacteria communicate with each other via secreted sensing molecules. Several types of the molecules have been identified. However, the mechanisms of control remain to be established. This pattern for bacteria growth and toxin production is also observed when quorum-sensing molecules of homoserine lactone and indole are added to the media prior to inoculation.