Rapid detection of Escherichia coli O157:H7 in ground beef using a fiber-optic biosensor.
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.
DeMarco
D R
DR
Department of Biology, University of South Florida, Tampa 33620, USA.
Saaski
E W
EW
McCrae
D A
DA
Lim
D V
DV
D000818:Animals; D015374:Biosensing Techniques / Q000295:instrumentation*; D002417:Cattle; D019453:Escherichia coli O157 / Q000302:isolation & purification*; D005336:Fiber Optic Technology; D008460:Meat / Q000382:microbiology*; D055100:Optical Fibers; D012680:Sensitivity and Specificity