Department of Electronic Engineering (DEIS), University of Bologna, Bologna, Italy.
Biosens Bioelectron. 2010 Nov 15;26(3):983-90. doi: 10.1016/j.bios.2010.08.039. Epub 2010 Aug 20.
Microbial screening is a primary concern for many products. Traditional techniques based on standard plate count (SPC) are accurate, but time consuming. Furthermore, they require a laboratory environment and qualified personnel. The impedance technique (IT) looking for changes in the electrical characteristics of the sample under test (SUT) induced by bacterial metabolism represents an interesting alternative to SPC since it is faster (3-12h vs. 24-72 h for SPC) and can be easily implemented in automatic form. With this approach, the essential parameter is the time for bacteria concentration to reach a critical threshold value (about 10(7) cfu mL(-1)) capable of inducing significant variations in the SUT impedance, measured by applying a 100 mV peak-to-peak 200 Hz sinusoidal test signal at time intervals of 5 min. The results of this work show good correlation between data obtained with the SPC approach and with impedance measurements lasting only 3h, in the case of highly contaminated samples (10(6) cfu mL(-1)). Furthermore, this work introduces a portable system for impedance measurements composed of an incubation chamber containing the SUT, a thermoregulation board to control the target temperature and an impedance measurement board. The mix of cheap electronics and fast detection time provides a useful tool for microbial screening in industrial and commercial environments.
微生物筛选是许多产品的首要关注点。基于标准平板计数（SPC）的传统技术准确，但耗时。此外，它们需要实验室环境和合格的人员。阻抗技术（IT）通过寻找细菌代谢引起的测试样品（SUT）的电特性变化，代表了对 SPC 的一个有趣替代，因为它更快（3-12h 与 SPC 的 24-72 h 相比），并且可以很容易地以自动形式实现。使用这种方法，关键参数是细菌浓度达到临界阈值（约 10(7) cfu mL(-1))的时间，该时间足以在 SUT 阻抗中引起显著变化，通过在 5 分钟的时间间隔内施加 100 mV 峰峰值 200 Hz 正弦测试信号来测量。这项工作的结果表明，在高度污染的样品（10(6) cfu mL(-1))中，与仅持续 3 小时的阻抗测量相比，SPC 方法获得的数据之间存在良好的相关性。此外，这项工作引入了一种用于阻抗测量的便携式系统，该系统由一个包含 SUT 的孵育室、一个用于控制目标温度的热调节板和一个阻抗测量板组成。廉价电子设备和快速检测时间的结合为工业和商业环境中的微生物筛选提供了有用的工具。
