Internalization capacity of Salmonella enterica sv Thompson in strawberry plants via root

ABSTRACT Strawberry production represents an agriculture sector of high relevance for the Spanish economy, due to their strawberries, highly appreciated for their organoleptic characteristics and health benefits. However, the reported outbreaks in different countries by enteric pathogens associated with this product have increased the safety concerns among different stakeholders. A number of factors and pathways for introducing pathogens in the strawberry production chain has been investigated. However, information on the potential internalization of enteric pathogens in strawberries is still scarce. The present study aimed to evaluate the potential internalization of Salmonella enterica sv Thompson via root in strawberry plants under the application of successive contamination events through capillary irrigation. Strawberry plants were organized in three groups (16 plants per group), and they were submitted to different contamination scenarios; groups 1, 2 and 3 were irrigated 1, 2 and 3 times respectively, with 100 mL of water containing Salmonella Thompson (8.8 log10 CFU/mL) every other day for 9 days. Fruits, calyces, and leaves were analyzed during the experiment, while roots were analyzed on the 9th day. The results showed that all calyces analyzed were negative, while one strawberry sample (group 3; day 8), four leaves samples (groups 2 and 3; day 8) and one root sample (group 3; day 9) were positive for Salmonella Thompson, representing the 0.85% (95% C.I.: [0.02 – 4.63%]), 8.88% (95% C.I.: [2.48 – 21.22%]), and 2.22% (95% C.I.: [0.06 – 11.77%]), respectively, of the overall samples analyzed. A significant association between the increased frequency of contamination (three irrigations) and the presence of the pathogen in the samples was elucidated. Our findings, in comparison with other studies, also point out the importance of watering by drip irrigation as a more hygienic and safer agronomic practice than systems like sprinkling irrigation.