A concept sensor-based system to be integrated in an existing automated platform monitoring bacterial growth

摘要

Bacterial infections are still one of the main causes of disease around the world. For this reason, the early diagnosis of an infection becomes fundamental for patient's health. In the market, there are very advanced systems that perform such analyses on biological samples, such as WASPLab, by COPAN Italia S.p.A. This platform monitors the growth of bacterial cultures, in a fully automated way, by taking periodic images of the Petri dishes inoculated with bacteria. In this work, we describe the preliminary study on a concept sensor-based system that, when optimized, could be integrated in the WASPLab, to provide a more rapid and complete diagnosis response. The system measures the electrical impedance related to a Petri dish instrumented with an electrode-based sensor, only at two fixed frequencies. In addition, it presents quantitative information associated to bacterial growth to the user in real time. Such information comes under the form of parameters derived from impedance response. We tested the system through a specific experimental analysis. During repeated tests, we inoculated a Petri dish with an initial concentration equal to 1.5 McFarland of Staphylococcus Aureus ATC 6538. We have been monitoring its growth for 18 hours, while the dish was staying in an incubator at 35°C, by measuring the impedance at 100 Hz and 1000 Hz. After six hours, we observed a variation higher than 10% on the best parameter, which allowed finding a growth detection time of four hours. Achieved results demonstrate the validity of our approach, paving the way to the possibility to integrate our device in the WASPLab, to enhance its flexibility and diagnosis capabilities.