title: Risk factors for microbial contamination in fruits and vegetables at the preharvest level: a systematic review.
abstract: The objective of this study was to perform a systematic review of risk factors for contamination of fruits and vegetables with Listeria monocytogenes, Salmonella, and Escherichia coli O157:H7 at the preharvest level. Relevant studies were identified by searching six electronic  databases: MEDLINE, EMBASE, CAB Abstracts, AGRIS, AGRICOLA, and FSTA, using the following thesaurus terms: L. monocytogenes, Salmonella, E. coli O157 AND fruit, vegetable. All search terms were exploded to find all related subheadings. To be eligible, studies had to be prospective controlled  trials or observational studies at the preharvest level and had to show clear and sufficient information on the process in which the produce was contaminated. Of the 3,463 citations identified, 68 studies fulfilled the eligibility criteria. Most of these studies were on leafy greens and tomatoes.  Six studies assessed produce contamination with respect to animal host-related risk factors, and 20 studies assessed contamination with respect to pathogen characteristics. Sixty-two studies assessed the association between produce contamination and factors related to produce, water, and soil,  as well as local ecological conditions of the production location. While evaluations of many risk factors for preharvest-level produce contamination have been reported, the quality assessment of the reviewed studies confirmed the existence of solid evidence for only some of them, including  growing produce on clay-type soil, the application of contaminated or non-pH-stabilized manure, and the use of spray irrigation with contaminated water, with a particular risk of contamination on the lower leaf surface. In conclusion, synthesis of the reviewed studies suggests that reducing  microbial contamination of irrigation water and soil are the most effective targets for the prevention and control of produce contamination. Furthermore, this review provides an inventory of the evaluated risk factors, including those requiring more research.
authors.affiliation: Department of Veterinary Integrative Biosciences, Texas A&M University, College Station, TX 77843, USA. sspark@cvm.tamu.edu
authors.forename: Sangshin
authors.initials: S
authors.lastname: Park
authors.forename: Barbara
authors.initials: B
authors.lastname: Szonyi
authors.forename: Raju
authors.initials: R
authors.lastname: Gautam
authors.forename: Kendra
authors.initials: K
authors.lastname: Nightingale
authors.forename: Juan
authors.initials: J
authors.lastname: Anciso
authors.forename: Renata
authors.initials: R
authors.lastname: Ivanek
mesh_terms: D019453:Escherichia coli O157 / Q000254:growth & development / Q000302:isolation & purification; D005506:Food Contamination / Q000032:analysis*; D059022:Food Safety; D005638:Fruit / Q000382:microbiology*; D006801:Humans; D008089:Listeria monocytogenes / Q000254:growth & development / Q000302:isolation & purification; D012307:Risk Factors; D012475:Salmonella / Q000254:growth & development / Q000302:isolation & purification; D014675:Vegetables / Q000382:microbiology*