Carla Pinheiro

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Xylella fastidiosa is a xylem-limited, Gram-negative phytopathogenic bacterium responsible for severe diseases affecting a wide range of economically important crops worldwide. Its recent expansion into Europe has reinforced its status as a major quarantine pathogen. However, research on its physiology and antimicrobial susceptibility remains limited by its slow and fastidious growth under laboratory conditions, which typically requires 7–30 days for detectable development. We report a new laboratory-adapted culture medium, XFG; that supports robust growth of X. fastidiosa strain DSM 10026/PYCC 9740 in both liquid and solid formulations compatible with established physiological and antimicrobial testing protocols. In liquid culture, bacterial populations reached the stationary phase within three days, while visible and isolated colonies formed on solid medium within the same time frame. Growth kinetics were confirmed by optical density measurements, demonstrating a shortened lag phase and reproducible exponential growth. Proof-of-concept antimicrobial susceptibility testing revealed high sensitivity to rifampicin and tetracycline (MIC = 0.25 μg/mL), and to chloramphenicol and ampicillin (MIC = 0.99 μg/mL). These MIC values are consistent with those previously reported using conventional media, supporting the robustness and applicability of the proposed system. Overall, these results establish XFG as a system for reproducible X. fastidiosa growth under laboratory conditions, enabling high-throughput phenotyping of this important plant pathogen.

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