“Barcode” cell sensor offers rapid, low-cost, portable antimicrobial susceptibility testing

Researchers at the Hong Kong Baptist University (HKBU) have developed a portable antimicrobial susceptibility testing (AST) system with a barcode-like cell sensor and a companion smartphone app, allowing rapid, automatic, low-cost and microscope-free screening of samples in resource-limited settings or during infectious disease outbreaks.

The portable AST system has two main components: a cell culture zone consisting of microchannels where bacterial samples are exposed to various concentrations of a tested antibiotic, and a “barcode” cell sensor zone containing an array of adaptive linear filters arranged in parallel that resembles a barcode structure. [Biosens Bioelectron 2021;192:113516]

“After the culture period in the drug-admitted cell culture zone, bacteria are pushed to the downstream cell sensor zone. The suspended cells are concentrated here in the adaptive linear filters to form visible miniature bars, the lengths of which are generally proportional to the number of bacterial cells cultured under different concentrations of the tested antibiotic,” the researchers explained.

On-site screening is completed by scanning the barcode pattern with a smartphone app, which automatically records and analyzes the data to generate a minimum inhibitory concentration (MIC) value for the tested antibiotic based on the lengths of microbars.

The easy-to-use system offers a much shorter turnaround time (2–3 hours) than conventional AST methods (16–24 hours) and currently available automated AST systems (6.5–12 hours), both of which require laboratory equipment and skills. “It takes less than 15 minutes for the cultured cells to be pushed down to form the barcode pattern in the linear filters,” the researchers noted.

In addition, the system enables counting of a very small number of cells (approximately 1.00 x 10⁴ cells without pre-incubation), which could otherwise not be seen without a microscope. The production cost is low – estimated at <USD 1 per unit.

Testing of Escherichia coli and Staphylococcus aureus showed consistent MIC results between the “barcode” cell sensor and conventional AST, the researchers reported.

“Our novel platform for rapid, resource-independent, high throughput, and easy-to-use on-site AST can serve as a cost-efficient sample screening tool to quickly detect any sample with potential drug-resistant bacteria, which can then be sent for subsequent advanced analysis,” the researchers suggested.

Potential applications include on-site screening of food, water or facility samples, clinical AST in resource-limited settings, and urgent screening of large volumes of samples during outbreaks or pandemics.

“Our ‘barcode’ testing system is a promising new tool in the fight against antimicrobial resistance. It does not require advanced clinical facilities or professional testing skills,” said principal investigator, Dr Kangning Ren of the Department of Chemistry, HKBU.

A patent application has been filed for the novel system. “We plan to develop this into a portable AST device that can be used in resource-limited regions,” Ren added.

The portable system with a barcode-like microchannel structure has two main components: a cell culture zone (top) and a “barcode” cell sensor zone (bottom).