Agrochemicals indirectly increase survival of <i>E. coli</i> O157:H7 and indicator bacteria by reducing ecosystem services

Staley, Zachery R.; Rohr, Jason R.; Senkbeil, Jacob K.; Harwood, Valerie J.

doi:10.1890/13-1242.1

Cited by 37 publications

(25 citation statements)

References 57 publications

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“…Rather than removing vegetation, ranchers and growers could sequester pathogens by maintaining and/or installing vegetated buffers between crop fields and grazeable lands (25,26). Other alternatives include planting produce that is not eaten raw in areas adjacent to grazeable lands and reducing application of agrichemicals (i.e., herbicides and fungicides), which can increase EHEC through decreasing predatory and competitor bacterial abundance (34).…”

Section: Discussionmentioning

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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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: 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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“…In addition to density-mediated indirect effects, pesticides have the capacity to alter traits of organisms, such as behavior, immunity, physiology or morphology, resulting in trait-mediated indirect effects (Rohr and Crumrine, 2005; Rohr et al, 2003; Rohr, Kerby, and Sih, 2006; Rohr and Palmer, 2005; Rohr et al, 2008; Rohr et al, 2009). For example, upon exposure to an herbicide that affects photosynthesis, a facultatively heterotrophic protozoan (capable of photosynthetic or heterotrophic metabolism) might switch from an autotrophic to a heterotrophic mode, causing increased predation on the microbial prey population (an adverse effect) (Debenest et al, 2010; Staley et al, 2014). Pesticides might also stimulate an increase or decrease in anti-parasite or anti-predator behaviors, affecting overall survival (Rohr et al, 2009).…”

Section: Type and Direction Of Pesticide Effectsmentioning

confidence: 99%

“…In a study utilizing freshwater microcosms to assess the impact of atrazine (at 102 µg L −1 ) on competition and predation, no effect was observed on autochthonous protozoan predators; however, inoculated strains of Ent. faecalis and E. coli O157:H7 remained significantly elevated, likely a result of atrazine reducing autochthonous (naturally present) competitors (Staley et al, 2014). …”

Section: Specific Effects Of Pesticidesmentioning

confidence: 99%

A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems

Staley

Harwood

Rohr

2015

Critical Reviews in Toxicology

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Pesticides are a pervasive presence in aquatic ecosystems throughout the world. While pesticides are intended to control fungi, insects, and other pests, their mechanisms of action are often not specific enough to prevent unintended effects, such as on non-target microbial populations. Microorganisms, including algae and cyanobacteria, protozoa, aquatic fungi, and bacteria, form the basis of many food webs and are responsible for crucial aspects of biogeochemical cycling; therefore, the potential for pesticides to alter microbial community structures must be understood to preserve ecosystem services. This review examines studies that focused on direct population-level effects and indirect community-level effects of pesticides on microorganisms. Generally, insecticides, herbicides, and fungicides were found to have adverse direct effects on algal and fungal species. Insecticides and fungicides also had deleterious direct effects in the majority of studies examining protozoa species, although herbicides were found to have inconsistent direct effects on protozoans. Our synthesis revealed mixed or no direct effects on bacterial species among all pesticide categories, with results highly dependent on the target species, chemical, and concentration used in the study. Examination of community-level, indirect effects revealed that all pesticide categories had a tendency to reduce higher trophic levels, thereby diminishing top-down pressures and favoring lower trophic levels. Often, indirect effects exerted greater influence than direct effects. However, few studies have been conducted to specifically address community-level effects of pesticides on microorganisms and further research is necessary to better understand and predict the net effects of pesticides on ecosystem health.

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“…This study tested the hypothesis that LA35 persistence in environmental waters was consistent with that of FIB and various bacterial pathogens found in poultry feces. A 7-day incubation period was chosen, as the biphasic rapid decrease of bacteria followed by a lower rate of decline is readily observable in environmental or mesocosm studies (59,60). Longer incubation times have shown a continuation of the slow downward trend of most feces-associated bacteria until they reach undetectable levels (12).…”

Section: Discussionmentioning

confidence: 99%

LA35 Poultry Fecal Marker Persistence Is Correlated with That of Indicators and Pathogens in Environmental Waters

Weidhaas

Harwood

2015

Appl Environ Microbiol

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bDisposal of fecally contaminated poultry litter by land application can deliver pathogens and fecal indicator bacteria (FIB) into receiving waters via runoff. While water quality is regulated by FIB enumeration, FIB testing provides inadequate information about contamination source and health risk. This microbial source tracking (MST) study compared the persistence of the Brevibacterium sp. strain LA35 16S rRNA gene (marker) for poultry litter with that of pathogens and FIB under outdoor, environmentally relevant conditions in freshwater, marine water, and sediments over 7 days. Salmonella enterica, Campylobacter jejuni, Campylobacter coli, Bacteroidales, and LA35 were enumerated by quantitative PCR (qPCR), and Enterococcus spp. and E. coli were quantified by culture and qPCR. Unlike the other bacteria, C. jejuni was not detectable after 48 h. Bacterial levels in the water column consistently declined over time and were highly correlated among species. Survival in sediments ranged from a slow decrease over time to growth, particularly in marine microcosms and for Bacteroidales. S. enterica also grew in marine sediments. Linear decay rates in water (k) ranged from ؊0.17 day ؊1 for LA35 to ؊3.12 day ؊1 for C. coli. LA35 levels correlated well with those of other bacteria in the water column but not in sediments. These observations suggest that, particularly in the water column, the fate of LA35 in aquatic environments is similar to that of FIB, C. coli, and Salmonella, supporting the hypothesis that the LA35 marker gene can be a useful tool for evaluating the impact of poultry litter on water quality and human health risk.T he practice of applying poultry litter (bedding contaminated with feces) as fertilizer is the chosen method of disposal of several billion tons of litter per year in the United States (1, 2). Numerous studies have demonstrated the cause-and-effect relationship between land application of poultry litter and contamination of environmental waters and soils due to chemical and microbial pollution from runoff (3-6). The presence of pathogens such as Campylobacter jejuni, Salmonella enterica, and Staphylococcus aureus along with fecal indicator bacteria (FIB) such as enterococci and Escherichia coli in poultry litter is of particular concern from a public health perspective (7-10). The human disease risk associated with contamination of environmental water bodies with human fecal material is unambiguous; in contrast, the risk of disease from nonhuman fecal contamination (from animals and birds) is more variable and host dependent (11).Currently, water body contamination by fecal pollution is assessed by FIB levels. A body of literature has established that fecal coliforms, E. coli, and Enterococcus spp. can persist in environmental waters and in sediments (12-14), indicating the existence of extraintestinal reservoirs of FIB. The ability of enteric pathogens to persist in environmental waters and sediments is much less clear and almost certainly varies by pathogen type and species (13,15). A better ...

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Agrochemicals indirectly increase survival of E. coli O157:H7 and indicator bacteria by reducing ecosystem services

Cited by 37 publications

References 57 publications

Comanaging fresh produce for nature conservation and food safety

Comanaging fresh produce for nature conservation and food safety

A synthesis of the effects of pesticides on microbial persistence in aquatic ecosystems

LA35 Poultry Fecal Marker Persistence Is Correlated with That of Indicators and Pathogens in Environmental Waters

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