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A research team led by scientists from Hong Kong Baptist University (HKBU) has developed a new cell sensor with a barcode-like micro-channel structure that enables rapid and inexpensive screening for drug-resistant bacteria. .

The technology could potentially be used on a large scale in resource-limited situations such as frequent safety checks of water, food and public facilities, as well as urgent investigations of massive samples during a disease outbreak. infectious, especially in developing countries.

A research article on the new invention has been published in the international academic journal Biosensors and bioelectronics.

A fast and inexpensive testing approach

Photo: Cellular sensor with a barcode type micro-channel structure comprising two main parts; Source: HKBU, press release

Antibiotics are often used to treat bacterial infections, but the overuse and misuse of antibiotics has created the problem of drug resistance. Antimicrobial susceptibility testing (AST) is used to determine which antibiotics can effectively inhibit the growth of a certain type of bacteria.

However, conventional AST methods are too slow, as they require 16-24 hours to obtain results, while modern fast AST methods are expensive and require elaborate laboratory equipment. A rapid and cost-effective strategy is therefore needed to screen for bacterial samples on-site, with advanced laboratory tests organized only for those suspected of containing drug-resistant bacteria.

In response to this need, a research team led by Dr. Ren Kangning, Associate Professor in the Department of Chemistry at HKBU, designed a fully automatic, microscope-less AST system. It consists of two main parts: a cell culture zone and a “barcode” cell sensor. The cell culture area consists of a set of fluid-filled micro-channels that contain cell culture media as well as different concentrations of the antibiotic. The “bar code” cell sensor contains an array of “adaptive linear filters” arranged in parallel that resembles a “bar code” structure.

Users can complete the on-site screening within three hours by scanning the “barcode” with a mobile app developed by the researchers, and this will indicate if any drug-resistant pathogenic bacteria are present in the sample.

Amount of bacteria represented by the length of the bar

When performing AST with the system, bacterial samples will be injected and incubated in the cell culture area. The bacteria present in the test sample inside the microchannels show different proliferation rates depending on the different concentrations of the antibiotic.

Once the culture period is over, the bacterial cells will pass through the “adaptive linear filters”. Cells will not build up around the nanopores on the side walls of the microchannels, instead, they will be dragged down by the fluid and collected at the end of the microchannels.

The accumulated cells will then form visible vertical bars whose lengths are proportional to the quantity of bacterial cells cultured under the different concentrations of the antibiotic.

A mobile phone equipped with a macro lens can then be used to photograph the “barcode” created by the AST. The image will be analyzed automatically by the mobile application.

Results consistent with conventional AST

After the culture period, if all of the “bars” of the cell sensor have similar lengths, it means that the tested antibiotic cannot inhibit the growth of bacteria, and therefore the bacterial sample is resistant to the tested antibiotic. If the length of the “bars” is generally inversely proportional to the concentration of the antibiotic in the microchannels, this shows that the tested antibiotic is generally effective in preventing the growth of the bacteria, and therefore the bacteria is not. not medicated. resistant. When two adjacent “bars” show a marked difference in length, this indicates that the antimicrobial effect of the antibiotic jumps when its concentration reaches a particular level.

The research team tested E. coli and S. aureus with the “barcode” cell sensor and the results were consistent with those of the classic AST. The test can be completed in three hours, which is much faster than conventional AST. Microfluidic approaches developed by other researchers can also achieve comparable speeds, but they rely on expensive instruments for analysis in general.

Potential for use in resource-limited areas

The team’s barcode testing technology is a promising new tool in the fight against antimicrobial resistance. It is hoped that this will benefit routine screening for drug-resistant bacteria in the food industry, public spaces and healthcare facilities, as it does not require advanced clinical facilities and professional testing skills, said Dr. Ren.

The “barcode” cell sensor has a low production cost, and is estimated at less than US $ 1 per piece. The research team has applied for a patent for the “barcode” cellular sensor. The team plans to develop the technology into a portable AST instrument and ultimately hope it will be used in resource-limited areas.

In addition to researchers from the HKBU Chemistry Department, the “barcode” cell sensor research team also included scientists from the HKBU Computer Science Department and Stanford University School of Medicine.

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