Basil essential oil induces multifactorial stress in Klebsiella variicola : a potential natural strategy to control a foodborne pathogen

AIMS: Klebsiella variicola, traditionally considered a plant-associated bacterium, is emerging as a foodborne and opportunistic pathogen with growing antimicrobial resistance. Its persistence in food and food-processing environments represents a potential risk to public health. This study aimed to investigate how basil (Ocimum basilicum) essential oil (BEO), a plant-derived antimicrobial, affects the physiology of K. variicola and to identify molecular targets that could reduce its persistence in food-related environments. METHODS AND RESULTS: We applied a label-free quantitative proteomic approach to examine the global responses of K. variicola to a subinhibitory concentration of BEO. Exposure to BEO induced multifactorial stress responses, including altered membrane homeostasis, oxidative management, and translation processes. Key energy-related pathways were downregulated, while antioxidant defenses were upregulated, indicating that BEO imposes combined physiological stresses rather than acting through a single mechanism. CONCLUSIONS: These findings provide the first proteome-level insight into the cellular response of K. variicola to essential oils and highlight molecular vulnerabilities that could be exploited to limit its survival in food-processing settings. Overall, the study supports the potential of BEO as a natural antimicrobial strategy to improve food safety.