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 [1–3]. 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) [6–8]. 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
References
[1]
M.-L. Ackers, B. E. Mahon, E. Leahy et al., “An outbreak of Escherichia coli O157:H7 infections associated with leaf lettuce consumption,” Journal of Infectious Diseases, vol. 177, no. 6, pp. 1588–1593, 1998.
[2]
M. P. Doyle, “Reducing foodborne disease,” Food Technology, vol. 54, pp. 130–133, 2000.
[3]
E. D. Hilborn, J. H. Mermin, P. A. Mshar et al., “A multistate outbreak of Escherichia coli O157:H7 infections associated with consumption of mesclun lettuce,” Archives of Internal Medicine, vol. 159, no. 15, pp. 1758–1764, 1999.
[4]
R. L. Buchanan and M. P. Doyle, “Foodborne disease significance of Escherichia coli O157:H7 and other enterohemorrhagic E. coli,” Food Technology, vol. 51, no. 10, pp. 69–76, 1997.
[5]
Centers for Disease Control and Prevention, National Center for Infectious Diseases, and Division of Bacterial and Mycotic Diseases, “Escherichia coli O157:H7: general information,” September 2003, http://www.cdc.gov/.
[6]
M. Islam, M. P. Doyle, S. C. Phatak, P. Millner, and X. Jiang, “Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields treated with contaminated manure composts or irrigation water,” Journal of Food Protection, vol. 67, no. 7, pp. 1365–1370, 2004.
[7]
D. R. Fenlon, I. D. Ogden, A. Vinten, and I. Svoboda, “The fate of Escherichia coli and E. coli O157 in cattle slurry after application to land,” Journal of Applied Microbiology Symposium Supplement, vol. 88, no. 29, pp. 149s–156s, 2000.
[8]
J. V. Gagliardi and J. S. Karns, “Persistence of Escherichia coli O157:H7 in soil and on plant roots,” Environmental Microbiology, vol. 4, no. 2, pp. 89–96, 2002.
[9]
L. R. Beuchat, “Pathogenic microorganisms associated with fresh produce,” Journal of Food Protection, vol. 59, no. 2, pp. 204–216, 1996.
[10]
S. Wilhelm and A. O. Paulus, “How soil fumigation benefits the California strawberry industry,” Plant Diseases, vol. 64, pp. 264–270, 1980.
[11]
A. M. Ibekwe, S. K. Papiernik, J. Gan, S. R. Yates, C.-H. Yang, and D. E. Crowley, “Impact of Fumigants on Soil Microbial Communities,” Applied and Environmental Microbiology, vol. 67, no. 7, pp. 3245–3257, 2001.
[12]
R. S. Dungan, A. M. Ibekwe, and S. R. Yates, “Effect of propargyl bromide and 1,3-dichloropropene on microbial communities in an organically amended soil,” FEMS Microbiology Ecology, vol. 43, no. 1, pp. 75–87, 2003.
[13]
C. A. Heid, J. Stevens, K. J. Livak, and P. M. Williams, “Real time quantitative PCR,” Genome Research, vol. 6, no. 10, pp. 986–994, 1996.
[14]
R. D. Oberst, M. P. Hays, L. K. Bohra et al., “PCR-based DNA amplification and presumptive detection of Escherichia coli O157:H7 with an internal fluorogenic probe and the 5' nuclease (TaqMan) assay,” Applied and Environmental Microbiology, vol. 64, no. 9, pp. 3389–3396, 1998.
[15]
P. M. Fratamico, M. Y. Deng, T. P. Strobaugh, and S. A. Palumbo, “Construction and characterization of Escherichia coli O157:H7 strains expressing firefly luciferase and green fluorescent protein and their use in survival studies,” Journal of Food Protection, vol. 60, no. 10, pp. 1167–1173, 1997.
[16]
A. M. Ibekwe and C. M. Grieve, “Changes in developing plant microbial community structure as affected by contaminated water,” FEMS Microbiology Ecology, vol. 48, no. 2, pp. 239–248, 2004.
[17]
D. T. Hoagland and D. I. Arnon, “The water culture methods for growing plants without soil. University of California (Berkeley) Agriculture Experiment Station,” Circ, vol. 237, 1950.
[18]
L. ？vre？s, L. Forney, F. L. Daae, and V. Torsvik, “Distribution of bacterioplankton in meromictic lake Saelenvannet, as determined by denaturing gradient gel electrophoresis of PCR-amplified gene fragments coding for 16S rRNA,” Applied and Environmental Microbiology, vol. 63, no. 9, pp. 3367–3373, 1997.
[19]
SAS Institute Inc., “SAS/STAT User's Guide,” Release 8.2. Cary, NC, 2001.
[20]
C. E. Shannon and W. Weaver, The Mathematical Theory of Communication, University of Illinois Press, Urbana, Ill, USA, 1963.
[21]
A. M. Ibekwe, P. M. Watt, C. M. Grieve, V. K. Sharma, and S. R. Lyons, “Multiplex fluorogenic real-time PCR for detection and quantification of Escherichia coli O157:H7 in dairy wastewater wetlands,” Applied and Environmental Microbiology, vol. 68, no. 10, pp. 4853–4862, 2002.
[22]
V. K. Sharma, “Detection and quantitation of enterohemorrhagic Escherichia coli O157, O111, and O26 in beef and bovine feces by real-time polymerase chain reaction,” Journal of Food Protection, vol. 65, no. 9, pp. 1371–1380, 2002.
[23]
L. Coroller, I. Leguerinel, E. Mettler, N. Savy, and P. Mafart, “General model, based on two mixed weibull distributions of bacterial resistance, for describing various shapes of inactivation curves,” Applied and Environmental Microbiology, vol. 72, no. 10, pp. 6493–6502, 2006.
[24]
I. Albert and P. Mafart, “A modified Weibull model for bacterial inactivation,” International Journal of Food Microbiology, vol. 100, no. 1–3, pp. 197–211, 2005.
[25]
E. Franz, M. M. Klerks, O. J. De Vos, A. J. Termorshuizen, and A. H. C. Van Bruggen, “Prevalence of Shiga toxin-producing Escherichia coli？？ , , eaeA, and rfbE genes and survival of E. coli O157:H7 in manure from organic and low-input conventional dairy farms,” Applied and Environmental Microbiology, vol. 73, no. 7, pp. 2180–2190, 2007.
[26]
X. Jiang, J. Morgan, and M. P. Doyle, “Fate of Escherichia coli O157:H7 in manure-amended soil,” Applied and Environmental Microbiology, vol. 68, no. 5, pp. 2605–2609, 2002.
[27]
M. Islam, J. Morgan, M. P. Doyle, and X. Jiang, “Fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and onions grown in an environmentally controlled growth chamber,” Journal of Food Protection, vol. 67, no. 3, pp. 574–578, 2004.
[28]
A. M. Ibekwe, P. M. Watt, P. J. Shouse, and C. M. Grieve, “Fate of Escherichia coli O157:H7 in irrigation water on soils and plants as validated by culture method and real-time PCR,” Canadian Journal of Microbiology, vol. 50, no. 12, pp. 1007–1014, 2004.
[29]
A. P. Williams, L. M. Avery, K. Killham, and D. L. Jones, “Persistence of Escherichia coli O157 on farm surfaces under different environmental conditions,” Journal of Applied Microbiology, vol. 98, no. 5, pp. 1075–1083, 2005.
[30]
L. M. Avery, K. Killham, and D. L. Jones, “Survival of E. coli O157:H7 in organic wastes destined for land application,” Journal of Applied Microbiology, vol. 98, no. 4, pp. 814–822, 2005.
[31]
J. M. Ritchie, G. R. Campbell, J. Shepherd et al., “A stable bioluminescent construct of Escherichia coli O157:H7 for hazard assessments of long-term survival in the environment,” Applied and Environmental Microbiology, vol. 69, no. 6, pp. 3359–3367, 2003.
[32]
E. Franz, A. V. Semenov, A. J. Termorshuizen, O. J. De Vos, J. G. Bokhorst, and A. H. C. van Bruggen, “Manure-amended soil characteristics affecting the survival of E. coli O157:H7 in 36 Dutch soils,” Environmental Microbiology, vol. 10, no. 2, pp. 313–327, 2008.
[33]
A. V. Semenov, E. Franz, L. Van Overbeek, A. J. Termorshuizen, and A. H. C. van Bruggen, “Estimating the stability of Escherichia coli O157:H7 survival in manure-amended soils with different management histories,” Environmental Microbiology, vol. 10, no. 6, pp. 1450–1459, 2008.
[34]
J. M. Schouten, E. A. M. Graat, K. Frankena, A. W. van De Giessen, W. K. van Der Zwaluw, and M. C. M. De Jong, “A longitudinal study of Escherichia coli O157 in cattle of a Dutch dairy farm and in the farm environment,” Veterinary Microbiology, vol. 107, no. 3-4, pp. 193–204, 2005.
[35]
A. Maule, “Survival of verocytotoxigenic Escherichia coli O157 in soil, water and on surfaces,” Journal of Applied Microbiology Symposium Supplement, vol. 88, no. 29, pp. 71S–78S, 2000.
[36]
E. Franz, A. D. van Diepeningen, O. J. De Vos, and A. H. C. van Bruggen, “Effects of cattle feeding regimen and soil management type on the fate of Escherichia coli O157:H7 and Salmonella enterica serovar typhimurium in manure, manure-amended soil, and lettuce,” Applied and Environmental Microbiology, vol. 71, no. 10, pp. 6165–6174, 2005.
[37]
A. Fernández, M. López, A. Bernardo, S. Condón, and J. Raso, “Modelling thermal inactivation of Listeria monocytogenes in sucrose solutions of various water activities,” Food Microbiology, vol. 24, no. 4, pp. 372–379, 2007.
[38]
M. A. J. S. Van Boekel, “On the use of the Weibull model to describe thermal inactivation of microbial vegetative cells,” International Journal of Food Microbiology, vol. 74, no. 1-2, pp. 139–159, 2002.
[39]
M. Peleg, “Microbial survival curves: interpretation, mathematical modeling, and utilization,” Comments Theory of Biology, vol. 8, pp. 357–387, 2003.
[40]
J. D. van Elsas, P. Hill, A. Chroňková et al., “Survival of genetically marked Escherichia coli O157:H7 in soil as affected by soil microbial community shifts,” ISME Journal, vol. 1, no. 3, pp. 204–214, 2007.
[41]
J. A. van Veen, L. S. van Overbeek, and J. D. van Elsas, “Fate and activity of microorganisms introduced into soil,” Microbiology and Molecular Biology Reviews, vol. 61, no. 2, pp. 121–135, 1997.
[42]
A. M. Ibekwe, C. M. Grieve, and C.-H. Yang, “Survival of Escherichia coli O157:H7 in soil and on lettuce after soil fumigation,” Canadian Journal of Microbiology, vol. 53, no. 5, pp. 623–635, 2007.
[43]
A. M. Ibekwe, P. J. Shouse, and C. M. Grieve, “Quantification of survival of Escherichia coli O157:H7 on plants affected by contaminated irrigation water,” Engineering in Life Sciences, vol. 6, no. 6, pp. 566–572, 2006.
