Rapid antibiotic susceptibility testing (AST) is critical in determining bacterial resistance or susceptibility to a particular antibiotic. Simple-to-use phenotype-based AST platforms can assist care-givers in timely prescription of the right antibiotic. Monitoring the change of bacterial viability by measuring electrochemical Faradaic current is a promising approach for rapid AST. However, the existing works require mixing redox-active reagents in the solution which can interfere with the antibiotics. In this paper, we developed a facile electrodeposition process for creating a redox-active crystalline layer (denoted as RZx) on pyrolytic graphite sheets (PGS), which was then utilized as the sensing layer for reagent-free electrochemical AST. To demonstrate the proof-of-principle, we tested the sensors with Escherichia coli (E. coli) K-12 treated with two antibiotics, ampicillin and kanamycin. While the sensors enable detection of bacterial metabolism mainly due to pH-sensitivity of RZx (∼ 53 mV/pH), secreted redox-active metabolites/compounds from whole cells are likely contributing to the signal as well. By monitoring the differential voltammetric signals, the sensors enable accurate prediction of the minimum inhibitory concentration (MIC) in 60 min (p < 0.03). The sensors are stable after 60 days storage in ambient conditions and enable analysis of microbial viability in complex solutions, as demonstrated in spiked milk and human whole blood.

快速抗生素敏感性测试（AST）对于确定细菌对特定抗生素的耐药性或敏感性至关重要。基于表型的易于使用的AST平台可以帮助护理人员及时开出正确的抗生素处方。通过测量电化学法拉第电流来监测细菌生存力的变化是快速AST的有前途的方法。然而，现有的工作需要在溶液中混合氧化还原活性试剂，这会干扰抗生素。在本文中，我们开发了一种简便的电沉积工艺，以在热解石墨片（PGS）上创建氧化还原活性晶体层（表示为RZx），然后将其用作无试剂电化学AST的传感层。为了证明原理，我们使用大肠杆菌（大肠杆菌）K-12具有两个抗生素治疗，氨苄青霉素和卡那霉素。虽然传感器主要由于RZx的pH敏感性（〜53 mV / pH）能够检测细菌代谢，但全细胞分泌的氧化还原活性代谢产物/化合物也可能对信号产生影响。通过监测差分伏安信号，传感器可以在60分钟内准确预测最小抑菌浓度（MIC）（p  <0.03）。传感器在环境条件下储存60天后稳定，并且能够分析复杂溶液中的微生物活力，如加标牛奶和人类全血中所证明的那样。