Evaluation of meteorological factors associated with pre-harvest contamination risk of generic Escherichia coli in a mixed produce and dairy farm

Abstract

Produce products from mixed farms may be at risk due to its unique setting and practice. This study aimed to identify specific meteorological factors affecting the presence and population levels of generic Escherichia coli (as an indicator for fecal contamination) in a mixed produce and dairy farm. Over 14 months, environmental samples were collected from locations within a mixed produce and dairy farm, and enumerated for generic E. coli. Local weather factors were evaluated for their association with the presence of generic E. coli by using logistic regression and classification tree method. In addition, negative binomial and regression tree models were developed to identify factors affecting population levels of generic E. coli from a sample location. The developed models identified monthly precipitation and monthly temperature as risk factors. The higher prevalence or higher population levels of generic E. coli were observed under higher average precipitation (>1.4 mm) and higher average temperature (>20.2 °C) in the previous 30 days. However, prevalence and population level of generic E. coli were negatively correlated with precipitation and wind speed at day 2 before sampling, suggesting that higher precipitation (>0.5 mm) and higher wind speed (>2.5 m/s) two days before sampling may lower the prevalence and count of generic E. coli within the mixed farm. Results suggest that presence and population level of E. coli in mixed farms is influenced by temperature, precipitation, and wind speed. Meteorological factors should be considered when evaluating farm management practices to reduce pre-harvest pathogen contamination.