Rapid Detection of Escherichia coli O157:H7 in Ground Beef Using a Fiber-Optic Biosensor

Abstract

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.

Rapid Ultrafiltration Concentration and Biosensor Detection of Enterococci from Large Volumes of Florida Recreational Water

“…Detection limits of biological targets in complex matrices average 10 4 to 10 5 CFU/ml (8,9,23,24,46). Hollow-fiber ultrafiltration provides significant concentration of cells from water with little increase in assay time and is currently the most promising technology for processing large volumes of water.…”

“…Although PCR assays can detect approximately 30 cells in a short time (14,17,20), the assays require a relatively "clean" sample that is free of inhibitors. Antibody-based biosensor assays have been performed on complex matrices, such as ground beef, apple juice, sprout irrigation waters, talc, chlorinated and chloraminated potable water, river water, and throat specimens (8,9,23,24,27,31,46). The following microorganisms have been detected within one or more of these matrices: Escherichia coli O157:H7, Salmonella enterica serovar Typhimurium, Bacillus anthracis, Bacillus atrophaeus, and vaccinia virus.…”

Method for Label-Free Detection of Femtogram Quantities of Biologics in Flowing Liquid Samples

“…This two-step procedure is used because in-liquid measurement is compromised because of viscous damping. The current methods capable of pathogen detection at low concentrations under liquid include traditional enrichment and plating methods in selective media, 52 polymerase chain reaction (PCR), 53 fiber-optic biosensors, 44,[54][55][56] immunomagnetic beads, 57 and quartz crystal microbalance. 58 Enrichment and plating approach lack sensitivity and specificity and often take 24-96 h to identify the contaminant organism.…”

Optical biosensors for food quality and safety assurance—a review

“…Application of antibody coupled fluorescence waveguide biosensor for detection of pathogens using fiber optic biosensors with detection limits was reviewed (Bhunia et al, 2007;Orellana and Haigh 2008). The fiber optic biosensors employing sandwich immunoassay coupled with fluorescent tagging were used to detect E. coli O157:H7 cells in ground beef rapidly at the levels of 3 to 30 CFU/mL (Demarco et al 1999), 5.2×10 2 CFU/g (Demarco and Lim 2002) and 10 3 CFU/mL . The commercial biosensor (Analyte 2000 of Research International, Washington) with no false positives could be easily adopted for field application with favourable cost economics.…”