Hydroponic systems are increasingly adopted for their high yields, efficient resource use, and year-round production of fresh produce. However, their nutrient-rich and controlled environments can also support the survival of foodborne pathogens such as Listeria monocytogenes and Salmonella enterica , posing a food safety challenge. Plant growth-promoting rhizobacteria (PGPR) are promising biocontrol agents that enhance plant health but could also suppress human pathogens in soilless systems. This study investigated the efficacy of three commercial bioinoculants: a multibacillus- Trichoderma harzianum consortium (TG), Bacillus subtilis QST 713 (SN), and Streptomyces lydicus WYEC 108 (AC) against L. monocytogenes and S. Typhimurium in basil grown under deep-water culture (DWC) and nutrient film technique (NFT) systems. Results demonstrated that PGPR significantly reduced Listeria but not Salmonella , with effectiveness dependent on bioinoculant type, system, and production stage. TG was the most effective PGPR, with a significantly higher reduction of5.38±0.10 log reduction in NFT (p < 0.05), corresponding to complete elimination of Listeria from the roots by day 28. In contrast, AC consistently sustained higher pathogen survival, often exceeding that of uninoculated controls. These findings reveal that commercial PGPR bioinoculants can serve as a viable and effective strategy for mitigating and controlling the persistence of Listeria monocytogenes and Salmonella Typhimurium in hydroponic production systems. Still, their efficacy is highly context-dependent, shaped by the pathogen, PGPR composition, hydroponic system design, and production cycle stage. Integrating PGPR into hydroponics holds promise for enhancing microbial safety of fresh produce, but bioinoculant selection must be tailored to system and pathogen dynamics.
Akumu et al. (Mon,) studied this question.