Rapid detection of Escherichia coli O157:H7 in ground beef using a fiber-optic biosensor

• Published in: Journal of food protection Vol. 62; no. 7; p. 711
• Main Authors: DeMarco, D R, Saaski, E W, McCrae, D A, Lim, D V
• Format: Journal Article
• Language: English
• Published: United States 01-07-1999
• Subjects: Animals; Biosensing Techniques - instrumentation; Cattle; Escherichia coli O157 - isolation & purification; Fiber Optic Technology; Meat - microbiology; Optical Fibers; Sensitivity and Specificity
• ISSN: 0362-028X
• DOI: 10.4315/0362-028X-62.7.711

A portable fiber-optic biosensor was used to detect Escherichia coli O157:H7 in seeded ground beef samples. The principle of the system is a sandwich immunoassay using cyanine 5 dye-labeled polyclonal anti-E. coli O157:H7 antibodies for generation of a specific fluorescent signal. Signal acquisition is effected by launching light from a 635-nm diode laser into a dual tapered 600-microm silica fiber. Fluorescent molecules within approximately 100 nm of the fiber surface are excited by the evanescent field, and a portion of the emission recouples into the fiber. A photodiode allows for quantitation of the collected emission light at wavelengths of 670 to 710 nm. Biotin-avidin interactions are used to attach polyclonal antibodies specific for E. coli O157:H7 to the final 7.5 cm of the fiber probe. The biosensor was able to detect E. coli O157:H7 to 3 to 30 CFU/ml in seeded ground beef samples. The reaction was highly specific. Signals with Listeria monocytogenes, Salmonella Typhimurium, or E. coli nonO157:H7 were 2 to 3% of those observed with a similar concentration of E. coli O157:H7. Assays were conducted at or near real-time with results obtained within 20 min of sampling.