Microfluidic Array Enables Rapid Testing of Natural Compounds Against Xylella fastidiosa

The bacterial pathogen <i>Xylella fastidiosa</i> (<i>Xf</i>), which causes several plant diseases with significant economic impacts on agriculture and the environment, remains a challenge to manage due to its wide host range. This study investigated the <i>in vitro</i> antibacterial effects of natural compounds, including <i>Trametes versicolor</i> extract, clove essential oil, and the resistance inducer Fossil^Ⓡ, against <i>X. fastidiosa</i> subsp. <i>fastidiosa</i> using an antibacterial susceptibility testing (AST) method based on microfluidic channels. This novel method was compared with the traditional broth macrodilution method to assess its reliability and the potential advantages microfluidics offers. For each substance and test, both the ability to limit planktonic growth (reported as the minimum inhibitory concentration) and the ability to inhibit biofilm formation were evaluated. The results suggest that compared to the macrodilution method, microfluidic channels allow for a more rapid AST execution, use less material, and allow for real-time observation of bacterial behavior under a continuous flow of nutrients and antibacterial substances. All tested products demonstrated high antibacterial efficacy against <i>Xf</i> with the macrodilution method, yielding comparable results with microfluidic AST. These findings highlight the antimicrobial properties of the tested substances and establish the groundwork for applying this new technique to select promising eco-friendly products for potential future field applications in controlling <i>Xf</i>.