Quantitative contamination assessment of Escherichia coli in baby spinach primary production in Spain : effects of weather conditions and agricultural practices

A quantitative microbial contamination model of Escherichia colt during primary production of baby spinach was developed. The model included only systematic contamination routes (e.g. soil and irrigation water) and it was used to evaluate the potential impact of weather conditions, agricultural practices as well as bacterial fitness in soil on the E. colt levels present in the crop at harvest. The model can be used to estimate E. colt contamination of baby spinach via irrigation water, via soil splashing due to irrigation water or rain events, and also including the inactivation of E. colt on plants due to solar radiation during a variable time of culturing before harvest. Seasonality, solar radiation and rainfall were predicted to have an important impact on the E. colt contamination. Winter conditions increased E. colt prevalence and levels when compared to spring conditions. As regards agricultural practices, both water quality and irrigation system slightly influenced E. colt levels on baby spinach. The good microbiological quality of the irrigation water (average E. colt counts in positive water samples below 1 log/100 mL) could have influenced the differences observed among the tested agricultural practices (water treatment and irrigation system). This quantitative microbial contamination model represents a preliminary framework that assesses the potential impact of different factors and intervention strategies affecting E. colt concentrations at field level. Taking into account that E. colt strains may serve as a surrogate organism for enteric bacterial pathogens, obtained results on E. colt levels on baby spinach may be indicative of the potential behaviour of these pathogens under defined conditions.A quantitative microbial contamination model of Escherichia colt during primary production of baby spinach was developed. The model included only systematic contamination routes (e.g. soil and irrigation water) and it was used to evaluate the potential impact of weather conditions, agricultural practices as well as bacterial fitness in soil on the E. colt levels present in the crop at harvest. The model can be used to estimate E. colt contamination of baby spinach via irrigation water, via soil splashing due to irrigation water or rain events, and also including the inactivation of E. colt on plants due to solar radiation during a variable time of culturing before harvest. Seasonality, solar radiation and rainfall were predicted to have an important impact on the E. colt contamination. Winter conditions increased E. colt prevalence and levels when compared to spring conditions. As regards agricultural practices, both water quality and irrigation system slightly influenced E. colt levels on baby spinach. The good microbiological quality of the irrigation water (average E. colt counts in positive water samples below 1 log/100 mL) could have influenced the differences observed among the tested agricultural practices (water treatment and irrigation system). This quantitative microbial contamination model represents a preliminary framework that assesses the potential impact of different factors and intervention strategies affecting E. colt concentrations at field level. Taking into account that E. colt strains may serve as a surrogate organism for enteric bacterial pathogens, obtained results on E. colt levels on baby spinach may be indicative of the potential behaviour of these pathogens under defined conditions.A