%0 Journal Article
%T Quantification of Persistence of Escherichia coli O157:H7 in Contrasting Soils
%A A. Mark Ibekwe
%A Sharon K. Papiernik
%A Catherine M. Grieve
%A Ching-Hong Yang
%J International Journal of Microbiology
%D 2011
%I Hindawi Publishing Corporation
%R 10.1155/2011/421379
%X Persistence of Escherichia coli (E. coli) O157:H7 in the environment is a major concern to vegetable and fruit growers where farms and livestock production are in close proximity. The objectives were to determine the effects of preplant fumigation treatment on the survival of E. coli O157:H7 in two soils and the effects of indigenous bacterial populations on the survival of this pathogen. Real-time PCR and plate counts were used to quantify the survival of E. coli O157:H7 in two contrasting soils after fumigation with methyl bromide (MeBr) and methyl iodide (MeI). Ten days after fumigation, E. coli O157:H7 counts were significantly lower ( ) in fumigated soils than in the non-fumigated. Direct comparison between MeBr and MeI within each soil indicated that these two fumigants showed similar impacts on E. coli O157:H7 survival. Microbial species diversity as determined by DGGE was significantly higher in clay soil than sandy soil and this resulted in higher initial decline in population in clay soil than in sandy soil. This study shows that if soil is contaminated with E. coli O157:H7, fumigation alone may not eliminate the pathogen, but may cause decrease in microbial diversity which may enhance the survival of the pathogen. 1. Introduction Appropriate management of farm waste such as manure is critical in controlling the spread of pathogens such as E. coli O157:H7 to vegetable crops. In most management schemes, fumigants are used for the control of plant pathogens, nematodes, and weeds before high-value cash crops such as strawberry and tomato are planted. Outbreaks of E. coli O157:H7 infections historically have been associated with consumption of undercooked ground beef; however, many recent outbreaks have resulted from consumption of contaminated raw vegetables, including lettuce [1¨C3]. Although many pathogens have been associated with fresh produce, E. coli O157:H7 is of particular concern because ingestion of relatively few cells can cause illness [4]. E. coli O157:H7 can survive for 60 to 120 days in water and in soil, and under dry and acidic conditions [5]. The steps in the production chain that have the greatest potential for pathogen contamination are soil preparation (use of uncomposted manures) and planting and growing (use of contaminated irrigation water and animal manures and manure from animals grazing locally or nearby) [6¨C8]. Prevention of preharvest contamination of fresh produce is an essential part of systems approach focused on interventions designed to achieve delivery of microbiological safe produce to consumers [9]. Suppression
%U http://www.hindawi.com/journals/ijmicro/2011/421379/