title: Proliferation of Escherichia coli O157:H7 in Soil-Substitute and Hydroponic Microgreen Production Systems.
abstract: Radish (Raphanus sativus var. longipinnatus) microgreens were produced from seeds inoculated with Escherichia coli O157:H7 by using peat moss-based soil-substitute and hydroponic production systems. E. coli populations on the edible and inedible parts of harvested microgreen plants (7 days postseeding) and in growth medium were examined. E. coli O157:H7 was shown to survive and proliferate significantly during microgreen growth in both production systems, with a higher level in the hydroponic production system. At the initial seed inoculation level of 3.7 log CFU/g, E. coli O157:H7 populations on the edible part of microgreen plants reached 2.3 and 2.1 log CFU/g (overhead irrigation and bottom irrigation, respectively) for microgreens from the soil-substitute production system and reached 5.7 log CFU/g for those hydroponically grown. At a higher initial inoculation of 5.6 log CFU/g seeds, the corresponding E. coli O157:H7 populations on the edible parts of microgreens grown in these production systems were 3.4, 3.6, and 5.3 log CFU/g, respectively. Examination of the spatial distribution of bacterial cells on different parts of microgreen plants showed that contaminated seeds led to systematic contamination of whole plants, including both edible and inedible parts, and seed coats remained the focal point of E. coli O157:H7 survival and growth throughout the period of microgreen production.
authors.affiliation: Environmental Microbial and Food Safety Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA; Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20740, USA.
authors.forename: Zhenlei
authors.initials: Z
authors.lastname: Xiao
authors.affiliation: Electron and Confocal Microscopy Unit, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA.
authors.forename: Gary
authors.initials: G
authors.lastname: Bauchan
authors.affiliation: Environmental Microbial and Food Safety Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA.
authors.forename: Lydia
authors.initials: L
authors.lastname: Nichols-Russell
authors.affiliation: Environmental Microbial and Food Safety Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA.
authors.forename: Yaguang
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Department of Nutrition and Food Science, University of Maryland, College Park, Maryland 20740, USA.
authors.forename: Qin
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Environmental Microbial and Food Safety Laboratory, U.S. Department of Agriculture, Agricultural Research Service, Beltsville, Maryland 20705, USA. xiangwu.nou@ars.usda.gov.
authors.forename: Xiangwu
authors.initials: X
authors.lastname: Nou
mesh_terms: D015169:Colony Count, Microbial; D019453:Escherichia coli O157 / Q000254:growth & development*; D005506:Food Contamination / Q000032:analysis; D005516:Food Microbiology; D018527:Hydroponics / Q000379:methods*; D018613:Microscopy, Confocal; D018515:Plant Leaves / Q000382:microbiology; D018517:Plant Roots / Q000382:microbiology; D031224:Raphanus / Q000382:microbiology; D012639:Seeds / Q000382:microbiology; D012988:Soil Microbiology