OPTICAL METHODS FOR DETECTING ESCHERICHIA COLI 0157:H7 SPIKED ON CANTALOUPES

Authors: Tu, Shu I; Uknalis, Joseph; Gehring, Andrew

Submitted to: Proceedings of SPIE
Publication Type: Proceedings
Publication Acceptance Date: 10/15/2004
Publication Date: 10/25/2004
Citation: Tu, S., Uknalis, J., Gehring, A.G. 2004. Optical methods for detecting escherichia coli 0157:h7 spiked on cantaloupes. Proceedings of SPIE. 5587. pp. 183-189.

Interpretive Summary:

Technical Abstract: Outbreaks of E. coli O157:H7 by the consumption of contaminated cantaloupes have been documented. Pathogens harbored in the networked but porous veins in the khaki colored skin of cantaloupes are difficult to remove. Thus, sensitive and efficient methods are needed to detect the presence of E. coli O157:H7 in cantaloupes. In this work, known quantities (3.18 x 10(2) to 3.18 x 10(6) CFU/cm(2) of the E. coli were placed on cantaloupe skins at room temperature for 1 h to allow bacteria to bind. The contaminated samples were transferred to stomacher bags filled with EC+novobiocin broth and stomachered for 30 s. The resulting suspensions were incubated at 37 degrees C for 3.3h. The bacteria in the slurry captured by magnetic beads coated with anti E. coli O157 antibodies were further sandwiched by second anti E. coli O157 antibodies containing peroxidase for chemiluminescent measurements of captured bacteria. Alternatively, the captured bacteria were treated with electron-shuttering reagent, e.g., menadione, to detect the cellular level of NAD(P)H via bioluminescence. The detected enzyme activity (peroxidase) and the NAD(P)H were used to measure the presence of the pathogen. The results indicated both the chemiluminescence and the fluorescence methods, in 96 well microplate format, could be applied to detect the E. coli (3.18 x 10(2) CFU/cm(2)) contamination of cantaloupes.