The alarming dynamics of antibiotic-resistant infections calls for the development of rapid and point-of-care (POC) antibiotic susceptibility testing (AST) methods. Here, we demonstrated the first completely stand-alone microfluidic system that allowed the execution of digital enumeration of bacteria and digital antibiograms without any specialized microfluidic instrumentation. A four-chamber gravity-driven step emulsification device generated ∼2000 monodisperse 2 nanoliter droplets with a coefficient of variation of 8.9% of volumes for 95% of droplets within less than 10 minutes. The manual workload required for droplet generation was limited to the sample preparation, the deposition into the sample inlet of the chip and subsequent orientation of the chip vertically without an additional pumping system. The use of shallow chambers imposing a 2D droplet arrangement provided superior stability of the droplets against coalescence and minimized the leakage of the reporter viability dye between adjacent droplets during long-term culture. By using resazurin as an indicator of the growth of bacteria, we were also able to reduce the assay time to ∼5 hours compared to 20 hours using the standard culture-based test.

中文翻译：

---

重力驱动的微流体分析，用于细菌的数字计数和抗生素敏感性测试。

抗生素耐药性感染的惊人动态要求开发一种快速，即时的（POC）抗生素敏感性测试（AST）方法。在这里，我们展示了第一个完全独立的微流控系统，该系统无需任何专门的微流控仪器即可执行细菌的数字枚举和数字化抗菌素检测。一个四腔重力驱动的步骤乳化装置在不到10分钟的时间内产生了约2000个单分散的2纳升液滴，其中95％的液滴的变化系数为8.9％的体积。产生液滴所需的手动工作量仅限于样品制备，沉积在芯片样品入口中以及随后芯片垂直定向，而无需额外的泵送系统。施加2D液滴排列的浅室的使用提供了优异的液滴抗聚结稳定性，并使长期培养期间相邻液滴之间的报告活性染料的泄漏最小化。通过使用刃天青作为细菌生长的指示剂，我们也能够将测定时间减少到约5小时，而使用基于标准培养物的测试则为20小时。