Survival and Persistence of E. coli in Hydroponic Systems using Synthetic and Organic Fertilizers During Mint...

Hydroponics uses fertilizers that have readily available nutrients for plant growth. Studies have demonstrated the survival of human pathogens in hydroponic nutrient solutions. However, there are limited data on the influence of fertilizer composition and type on microbial contaminants. This study evaluated the survival, persistence, and distribution of E. coli ATCC 25922 in Nutrient Film Technique (NFT) and Deep-Water Culture (DWC) hydroponic systems using synthetic and organic fertilizers during mint production. E. coli ATCC 25922 was inoculated into mint-grown hydroponic systems with three synthetic and two organic (fish-based) nutrient solutions. Hydroponic solutions were collected for up to 39 days, and fully matured mint plants were harvested on day 40. The E. coli population, along with changes in physicochemical parameters and plant growth, was determined. E. coli levels decreased significantly (p < 0.05) in synthetic fertilizer systems after 24 h in both NFT and DWC systems. However, in fish-based fertilizer systems, the population increased significantly from 4.8 log CFU/mL to 8.51 log CFU/mL within 24 h, and the reduction rate was significantly lower in subsequent days than in synthetic nutrient solutions. Plant growth varied across fertilizer types. The organic hydroponic systems had significantly higher E. coli levels in mints, both edible parts and roots, compared to their counterparts. The findings of this study demonstrated a higher food safety risk associated with fish-based organic nutrient solutions than with synthetic fertilizers in hydroponic farming when contamination occurs.