Fast Antibacterial Susceptibility Testing by Measuring Electron Transfer Metabolism

Since some 2.8 million antibiotic-resistant infections occur annually in the United States with more than 35,000 fatalities, fast and simple antimicrobial susceptibility testing (AST) is urgently required to guide effective antibiotic usages and for monitoring of the antimicrobial resistance rate.

Towards this end, investigators at Binghamton University (NY, USA) established a rapid, quantitative, and high-throughput phenotypic AST by measuring electrons transferred from the interiors of microbial cells to external electrodes. Since the transferred electrons are based on microbial metabolic activities and are inversely proportional to the concentration of potential antibiotics, the changes in electrical outputs can be readily used as a signal to efficiently monitor bacterial growth and antibiotic susceptibility.

For this study, the investigators utilized the common Gram-negative pathogenic bacterium Pseudomonas aeruginosa together with the first-line antibiotic gentamicin. The novel detector had eight sensors printed on a paper surface. The minimum inhibitory concentration (MIC) values generated by the new technique were validated by the gold standard broth microdilution (BMD) method.

Results revealed that the new approach provided quantitative, actionable MIC results within just five hours, as it measured electricity produced by bacterial metabolism instead of the days needed for growth-observation methods.

"To effectively treat the infections, we need to select the right antibiotics with the exact dose for the appropriate duration," said senior author Dr. Seokheun Choi, associate professor of electrical and computer engineering at Binghamton University. "There is a need to develop an antibiotic-susceptibility testing method and offer effective guidelines to treat these infections."

"Although many bacteria are energy-producing, some pathogens do not perform extracellular electron transfer and may not be used directly in our platform. However, various chemical compounds can assist the electron transfer from non-electricity-producing bacteria," said Dr. Choi. "For instance, E. coli cannot transfer electrons from the inside of the cell to the outside, but with the addition of some chemical compounds, they can generate electricity. Now we are working on how to make this technique general to all bacteria cells. We leverage this biochemical event for a new technique to assess the antibiotic effectiveness against bacteria without monitoring the whole bacterial growth. As far as I know, we are the first to demonstrate this technique in a rapid and high-throughput manner by using paper as a substrate."

The new method for determining bacterial antibiotic resistance was published in the November 15, 2020 issue of the journal Biosensors and Bioelectronics.

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