Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: 9/11/2007
Publication Date: 9/20/2007
Citation: Tu, S., Uknalis, J., Gehring, A.G., He, Y. 2007. Application of horse-radish peroxidase linked chemiluminescence to determine the production mechanism of Shiga-like toxins by E. coli O157:H7. Proceedings of SPIE.#6761 Interpretive Summary: The Centers for Disease Control have estimated that E. coli O157:H7 bacteria cause 73,000 cases of serious illness and 61 deaths in the United States each year. The illness has been associated with the Shiga-like toxins (SLTs) secreted by the bacteria. Thus, there is a need to develop sensitive, specific and rapid detection of the bacteria and their SLTs. We have developed a new biosensor assay based on an antibody approach to detect both E. coli O157:H7 and the SLTs from the same food samples. We also found that the presence of other non-toxin bacteria did not affect the growth of E. coli O157:H7 but did substantially decrease the production of SLTs. This information is valuable for researchers to develop practical conditions for assaying the presence of SLTs in complex food matrices.
Technical Abstract: A sandwiched immunoassay consisting of toxin capture by immunomagnetic beads (IMB) and toxin detection by horseradish peroxidase (HRP) linked chemiluminescence was used to follow the production of Shiga-like toxins (SLT) by E. coli O157:H7. The intensity of luminescence generated by the oxidation of luminol-liked compounds was used to represent the concentration of toxins produced. The time-course of SLT production by E. coli O157:H7 under different conditions was investigated. In pure culture, optimal generation of SLT showed a significant delay than the steady state of cell growth. In mixed cultures of SLT producing E. coli O157:H7 and non-SLT producing E. coli K-12 strain, the production of toxins was substantially decreased. However, the growth of E. coli O157:H7 was not affected by the presence of K-12 strain. This decrease in SLT production was also observed in radiation-sterile ground beef. In regular ground beef that might contain numerous other bacteria, the growth of E. coli O157:H7 in EC media was not significantly affected but the lowered production of SLT was observed. The results showed that mechanism of inducing SLT production was complex with both the growth time and growth environment could influence SLT production. The addition of homo-serine lactone to the growth media enhanced the production of SLT. Thus, possibly cell-cell communication may have a role in SLT production by E. coli O157:H7.