Occurrence of generic Escherichia coli, E. coli O157 and Salmonella spp. in water and sediment from leafy green produce farms and streams on the Central California coast

Benjamin, Lisa; Atwill, Edward R.; Jay-Russell, Michele; Cooley, Michael B.; Carychao, Diana; Gorski, Lisa; Mandrell, Robert E.

doi:10.1016/j.ijfoodmicro.2013.04.003

Cited by 139 publications

(138 citation statements)

References 64 publications

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“…2). Previous work also has shown that generic E. coli (18), E. coli O157:H7 (27), Salmonella (28), and Listeria (29,30) are positively associated with livestock density or proximity to livestock. Similarly, studies that have aggregated reported EHEC illnesses to county or district levels have generally observed higher EHEC infection rates in counties with higher cattle densities, although this approach infers rather than directly links cases and exposures (19,20).…”

Section: Discussionmentioning

confidence: 85%

“…Although some pathogens are sufficiently prevalent to enable investigation of the effects of surrounding landscape composition on pathogens (16), low pathogen prevalence generally constrains such investigations. One response to this situation has been to relate landscape features to indicators (e.g., generic E. coli) as a proxy for known pathogens (17,18). Another approach has been to assume that exposures result primarily from contact with local livestock or Significance Fresh produce has become the primary cause of foodborne illness in the United States.…”

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confidence: 99%

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Comanaging fresh produce for nature conservation and food safety

Karp

Gennet

Kilonzo

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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In 2006, a deadly Escherichia coli O157:H7 outbreak in bagged spinach was traced to California's Central Coast region, where >70% of the salad vegetables sold in the United States are produced. Although no definitive cause for the outbreak could be determined, wildlife was implicated as a disease vector. Growers were subsequently pressured to minimize the intrusion of wildlife onto their farm fields by removing surrounding noncrop vegetation. How vegetation removal actually affects foodborne pathogens remains unknown, however. We combined a fine-scale land use map with three datasets comprising ∼250,000 enterohemorrhagic E. coli (EHEC), generic E. coli, and Salmonella tests in produce, irrigation water, and rodents to quantify whether seminatural vegetation surrounding farmland is associated with foodborne pathogen prevalence in California's Central Coast region. We found that EHEC in fresh produce increased by more than an order of magnitude from 2007 to 2013, despite extensive vegetation clearing at farm field margins. Furthermore, although EHEC prevalence in produce was highest on farms near areas suitable for livestock grazing, we found no evidence of increased EHEC, generic E. coli, or Salmonella near nongrazed, seminatural areas. Rather, pathogen prevalence increased the most on farms where noncrop vegetation was removed, calling into question reforms that promote vegetation removal to improve food safety. These results suggest a path forward for comanaging fresh produce farms for food safety and environmental quality, as federal food safety reforms spread across ∼4.5 M acres of US farmland.agriculture | biodiversity | disease ecology | E. coli | foodborne pathogens

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Section: Discussionmentioning

confidence: 85%

mentioning

confidence: 99%

Comanaging fresh produce for nature conservation and food safety

Karp

Gennet

Kilonzo

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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“…Water has been iden-tified as a major reservoir for pathogens and irrigation as a vehicle for transmission of pathogens to fields and produce (12,30,41,(72)(73)(74)(75). L. monocytogenes is often found in various water sources, with reported prevalence from Ͻ1% to 29% (14,76,77).…”

Section: Field Practices Associated With Presence Of Pathogensmentioning

confidence: 99%

Risk Factors Associated with Salmonella and Listeria monocytogenes Contamination of Produce Fields

Strawn

Gröhn

Warchocki

et al. 2013

Appl Environ Microbiol

148

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cIdentification of management practices associated with preharvest pathogen contamination of produce fields is crucial to the development of effective Good Agricultural Practices (GAPs). A cross-sectional study was conducted to (i) determine management practices associated with a Salmonella-or Listeria monocytogenes-positive field and (ii) quantify the frequency of these pathogens in irrigation and nonirrigation water sources. Over 5 weeks, 21 produce farms in New York State were visited. Fieldlevel management practices were recorded for 263 fields, and 600 environmental samples (soil, drag swab, and water) were collected and analyzed for Salmonella and L. monocytogenes. Management practices were evaluated for their association with the presence of a pathogen-positive field. Salmonella and L. monocytogenes were detected in 6.1% and 17.5% of fields (n ‫؍‬ 263) and 11% and 30% of water samples (n ‫؍‬ 74), respectively. The majority of pathogen-positive water samples were from nonirrigation surface water sources. Multivariate analysis showed that manure application within a year increased the odds of a Salmonellapositive field (odds ratio [OR], 16.7), while the presence of a buffer zone had a protective effect (OR, 0.1). Irrigation (within 3 days of sample collection) (OR, 6.0), reported wildlife observation (within 3 days of sample collection) (OR, 6.1), and soil cultivation (within 7 days of sample collection) (OR, 2.9) all increased the likelihood of an L. monocytogenes-positive field. Our findings provide new data that will assist growers with science-based evaluation of their current GAPs and implementation of preventive controls that reduce the risk of preharvest contamination.

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“…Recent investigations have focused on irrigation water as a potential environmental source of Salmonella for preharvest contamination of produce (8)(9)(10)(11)12). Furthermore, the static nature of some irrigation ponds may sustain persistent populations of Salmonella (13,14).…”

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confidence: 99%

“…The recommended microbial standards for the quality of agricultural water that comes into direct contact with preharvest produce (other than sprouts) requires the threshold of generic Escherichia coli to be Ͻ410 most probable number (MPN)/100 ml for any single sample, with a geometric mean of Ͻ126 MPN/100 ml for all samples. Although this policy change will provide greater assurance of food safety, it may not be sufficient to eliminate risks from pathogens, such as Salmonella, that have shown little or no correlation between the level of the pathogen and that of generic E. coli (14,(16)(17)(18)(19)(20)(21)(22).…”

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confidence: 99%

Distribution and Characterization of Salmonella enterica Isolates from Irrigation Ponds in the Southeastern United States

Luo

Ginn

et al. 2015

Appl Environ Microbiol

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f Irrigation water has been implicated as a likely source of produce contamination by Salmonella enterica. Therefore, the distribution of S. enterica was surveyed monthly in irrigation ponds (n ‫؍‬ 10) located within a prime agricultural region in southern Georgia and northern Florida. All ponds and 28.2% of all samples (n ‫؍‬ 635) were positive for Salmonella, with an overall geometric mean concentration (0.26 most probable number [MPN]/liter) that was relatively low compared to prior reports for rivers in this region. Salmonella peaks were seasonal; the levels correlated with increased temperature and rainfall (P < 0.05). The numbers and occurrence were significantly higher in water (0.32 MPN/liter and 37% of samples) than in sediment (0.22 MPN/ liter and 17% of samples) but did not vary with depth. Representative isolates (n ‫؍‬ 185) from different ponds, sample types, and seasons were examined for resistance to 15 different antibiotics; most strains were resistant to streptomycin (98.9%), while 20% were multidrug resistant (MDR) for 2 to 6 antibiotics. DiversiLab repetitive extragenic palindromic-element sequence-based PCR (rep-PCR) revealed genetic diversity and showed 43 genotypes among 191 isolates, as defined by >95% similarity. The genotypes did not partition by pond, season, or sample type. Genetic similarity to known serotypes indicated Hadar, Montevideo, and Newport as the most prevalent. All ponds achieved the current safety standards for generic Escherichia coli in agricultural water, and regression modeling showed that the E. coli level was a significant predictor for the probability of Salmonella occurrence. However, persistent populations of Salmonella were widely distributed in irrigation ponds, and the associated risks for produce contamination and subsequent human exposure are unknown, supporting continued surveillance of this pathogen in agricultural settings.

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Occurrence of generic Escherichia coli, E. coli O157 and Salmonella spp. in water and sediment from leafy green produce farms and streams on the Central California coast

Cited by 139 publications

References 64 publications

Comanaging fresh produce for nature conservation and food safety

Comanaging fresh produce for nature conservation and food safety

Risk Factors Associated with Salmonella and Listeria monocytogenes Contamination of Produce Fields

Distribution and Characterization of Salmonella enterica Isolates from Irrigation Ponds in the Southeastern United States

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