Apparatus and Method for Detecting Microbial Contamination Rapid On-Site Pathogen Detection in Food, Water, and Bodily Fluids

This patent covers a rapid immunomagnetic and optical detection system for identifying food-borne pathogens such as E. coli O157:H7 and Salmonella in food, water, and bodily fluid samples, delivering results on-site in significantly less time than conventional laboratory culture methods.

The Problem

Foodborne pathogenic bacteria, including E. coli O157:H7 and Salmonella, are a major cause of illness and death worldwide. Testing food and water for these pathogens is a regulatory and public health necessity, but conventional culture and plating methods require days of incubation in properly equipped laboratories. The time delay between sampling and result means that contaminated product can enter the food supply before testing is complete, and that outbreak investigations run behind the spread of illness. Rapid testing methods that can reduce this delay — particularly methods that can be conducted on-site at food production facilities, distribution points, or in the field without specialist laboratory infrastructure — would directly improve food safety outcomes. The additional challenge is sensitivity: detecting as few as one viable cell per 125 grams of sample, the regulatory threshold for some pathogens, requires both efficient capture of the target organism from a complex matrix and a detection system sensitive enough to produce a readable signal from that low a concentration.

What This Invention Does

The invention combines immunomagnetic separation and optical detection in a streamlined workflow. A capture antibody (IgG class), linked to a magnetic particle 20 nm to 165 micrometres in diameter and coated with Protein A, is mixed with the sample. When the target pathogen is present, the capture antibody binds to a specific antigen on the bacterial surface, forming a first complex. A magnetic field separates this complex from the unbound sample matrix. A detector antibody (IgY class, lacking an IgG Fc region) linked to a detection moiety — either horseradish peroxidase or a fluorescent dye with excitation between 450 nm and 700 nm — is then added and binds to a distinct epitope on the same bacterial antigen, forming a sandwich complex. After separation of unbound detector antibody, the detection moiety is read on a portable optical instrument comprising an array of sample container positions, dedicated light sources, and photodetectors that convert the optical emission into a quantified signal. The system can detect concentrations as low as 0.008 to 0.078 cells per 125 grams and delivers results within approximately 30 minutes of an 8-hour enrichment step, compared with multiple days for conventional culture methods.

Key Features

• Immunomagnetic capture for high sensitivity. Magnetic particle-linked capture antibodies efficiently concentrate the target pathogen from large sample volumes, enabling detection at the single-cell-per-125-gram level required for regulatory food safety testing.
• IgG and IgY antibody pairing. Using an IgG capture antibody and an IgY detector antibody (which lacks an IgG Fc region) on distinct epitopes of the same antigen creates a highly specific sandwich format that minimises non-specific binding and background signal.
• Portable optical detection platform. The instrument contains an array of sample positions with individual light sources and photodetectors, enabling multi-sample parallel testing and quantitative output without a centralised laboratory spectrophotometer. Results are decoded digitally and can be delivered on-site.
• Broad pathogen applicability. While the patent specifically covers E. coli O157:H7 and Salmonella, the platform is designed to be adaptable to a range of foodborne bacterial pathogens by substituting the appropriate binding agents, enabling it to function as a multi-pathogen array.
• Dramatically reduced detection time. The combination of immunomagnetic concentration and optical detection reduces total time-to-result to approximately 8.5 hours (8 hours enrichment plus 30 minutes detection), a substantial improvement over 2-5 day conventional culture timelines.

Who Is Behind It?

The applicant and sole inventor is Majed El-Dweik, an independent researcher with a background in rapid microbiological detection methods. The Australian application is a divisional with a long lineage: AU 2024200122, AU 2022201210, and AU 2018266138 (the national phase of PCT/US2018/031679), with priority from two US provisional applications filed 8 May 2017. The Australian patent attorney is Spruson and Ferguson in Sydney.

Why It Matters

Australia’s food export industry — including beef, sheep meat, seafood, dairy, and fresh produce — depends on rigorous pathogen testing to maintain access to international markets. E. coli O157:H7 and Salmonella are among the most consequential foodborne pathogens for both domestic public health and export certification. A portable, rapid detection system that can be deployed at abattoirs, packing houses, export inspection points, and water treatment facilities, without sending samples to a central laboratory and waiting days, would meaningfully strengthen Australia’s food safety infrastructure. The low detection threshold (one cell per 125 grams) meets or exceeds regulatory requirements for major export markets, and the quantitative output of the optical platform provides documentation suitable for compliance records.

Related Concepts

This system combines two established principles: immunomagnetic separation, which concentrates target bacteria from complex matrices using antibody-coated magnetic particles, and sandwich immunoassay detection, in which two antibodies binding distinct epitopes on the same antigen generate a quantifiable signal. Together they enable highly sensitive, on-site pathogen identification.

Food safety testing requirements for pathogens such as E. coli O157:H7 and Salmonella are governed by regulators including Food Standards Australia New Zealand. Reducing time-to-result from days to hours directly supports outbreak prevention and export certification workflows across the agrifood supply chain.

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AU 2026201838 was published in the Australian Official Journal of Patents on 2 April 2026 and is open for public inspection. Patent applications represent inventions that are sought to be protected and do not necessarily reflect commercially available products.