title: Associations between weather and microbial load on fresh produce prior to harvest.
abstract: Contaminated produce causes approximately 1 million cases of foodborne illness and 1 billion dollars in damages to the U.S. economy annually. The environmental conditions, especially weather, that influence the inoculation, proliferation, and dispersal of microbial load on produce are not well understood. Using a mixed models approach, we examined the relationship of temperature and precipitation to microbial indicators of contamination on fresh produce on the farm over a week-long period prior to harvest. Between 2000 and 2002, we assayed for four microbial indicators of contamination (aerobic plate count, Enterococcus, total coliforms, and Escherichia coli) on 10 produce types in 15 fields in the southern United States. The sample collection times varied, with most occurring between January and May. We collected hourly weather data for the corresponding time period and location. Our results indicated that there was a significant association between the average daily temperature (20°C) and both log aerobic plate count (e.g., an increase of 0.074 log CFU/g [standard error {SE}, 0.023] per °C increase in weekly average temperature) and log Enterococcus (e.g., an increase of 0.15 log CFU/g [SE, 0.031] per °C increase in weekly average temperature) for approximately 5 days prior to sample collection. Daily total precipitation was significantly associated with log coliforms on 2 days (∼0.11 log CFU/g [SE, 0.06] per mm of precipitation) during the week-long lag period prior to harvest. Our results suggest that microbial indicator concentrations may increase as the temperature increases. Precipitation may have a positive but complex relationship with microbial indicators, as precipitation may create moist conditions conducive to bacterial growth, spread contamination onto the field, or wash contamination off of the plant.
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, 1518 Clifton Road N.E., Atlanta, Georgia 30322, USA.
authors.forename: Michelle
authors.initials: M
authors.lastname: Ward
authors.affiliation: Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road N.E., Atlanta, Georgia 30322, USA.
authors.forename: Radhika
authors.initials: R
authors.lastname: Dhingra
authors.affiliation: Department of Environmental Health, Rollins School of Public Health, Emory University, 1518 Clifton Road N.E., Atlanta, Georgia 30322, USA, Program in Population Biology, Ecology and Evolution, Graduate Division of Biological and Biomedical Sciences, Emory University, 1462 Clifton Road N.E., Atlanta, Georgia 30322, USA.
authors.forename: Justin V
authors.initials: JV
authors.lastname: Remais
authors.affiliation: Department of Biostatistics and Bioinformatics, Rollins School of Public Health, Emory University, 1518 Clifton Road N.E., Atlanta, Georgia 30322, USA.
authors.forename: Howard H
authors.initials: HH
authors.lastname: Chang
authors.affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Lynette M
authors.initials: LM
authors.lastname: Johnston
authors.affiliation: Department of Food, Bioprocessing, and Nutrition Sciences, North Carolina State University, Raleigh, North Carolina 27695, USA.
authors.forename: Lee-Ann
authors.initials: LA
authors.lastname: Jaykus
authors.affiliation: Hubert Department of Global Health, Rollins School of Public Health, Emory University, 1518 Clifton Road N.E., Atlanta, Georgia 30322, USA. juan.leon@emory.edu.
authors.forename: Juan
authors.initials: J
authors.lastname: Leon
mesh_terms: D058491:Bacterial Load; D018556:Crops, Agricultural / Q000254:growth & development / Q000382:microbiology*; D016983:Enterococcus / Q000302:isolation & purification; D004926:Escherichia coli / Q000302:isolation & purification; D005516:Food Microbiology; D005517:Foodborne Diseases; D011891:Rain; D013696:Temperature; D014481:United States; D014887:Weather