Abstract

Escherichia coli (E. coli) has been linked to multiple outbreaks of foodborne illness associated with the consumption of leafy vegetables. Typically, sanitizers only reduce microbiological load up to 2 log units, suggesting that pathogens survive inside the leaves. Contamination can occur in different crop production systems, such as field cultivation, cultivation in closed production systems, and hydroponic cultivation. Without proper safety measures, pathogenic microorganisms can contaminate leafy vegetables in hydroponic production systems. This study aimed to evaluate the survival of E. coli in chard plants (Beta vulgaris L. cv. SCR 107) whose nutrient solution was subjected to different doses of ozone (O3) (0, 0.5, and 2 mg L-1) for 3 min in floating root hydroponic culture. Furthermore, the study aimed to investigate the possible internalization of this bacteria in chard plants. Two experiments were conducted; the first consisted of applying O3 to the nutrient solution inoculated with 108 CFU mL-1 of E. coli. Survival and internalization of bacteria from the nutrient solution to the roots and leaves were measured by plate counts. In the second experiment, E. coli was introduced into the nutrient solution (108 CFU mL-1) and leaves (106 CFU mL-1) separately; subsequently, bacterial internalization was assessed by microscopy. The results indicated that, although the application of O3 reduced E. coli counts, the bacteria resisted the treatment and successfully penetrated the leaves of chard plants.