A longitudinal study to examine the influence of farming practices and environmental factors on pathogen prevalence using structural equation modeling.

The contamination of fresh produce with foodborne pathogens has been an on-going concern with outbreaks linked to these commodities. Evaluation of farm practices, such as use of manure, irrigation water source, and other factors that could influence pathogen prevalence in the farming environment could lead to improved mitigation strategies to reduce the potential for contamination events. Soil, water, manure, and compost were sampled from farms in Ohio and Georgia to identify the prevalence of Salmonella, Listeria monocytogenes (Lm), Campylobacter, and Shiga-toxin-producing Escherichia coli (STEC), as well as Arcobacter, an emerging human pathogen. This study investigated agricultural practices to determine which influenced pathogen prevalence, i.e., the percent positive samples. These efforts identified a low prevalence of Salmonella, STEC, and Campylobacter in soil and water (< 10%), preventing statistical modeling of these pathogens. However, Lm and Arcobacter were found in soil (13 and 7%, respectively), manure (49 and 32%, respectively), and water samples (18 and 39%, respectively) at a comparatively higher prevalence, suggesting different dynamics are involved in their survival in the farm environment. Lm and Arcobacter prevalence data, soil chemical characteristics, as well as farm practices and weather, were analyzed using structural equation modeling to identify which factors play a role, directly or indirectly, on the prevalence of these pathogens. These analyses identified an association between pathogen prevalence and weather, as well as biological soil amendments of animal origin. Increasing air temperature increased Arcobacter and decreased Lm. Lm prevalence was found to be inversely correlated with the use of surface water for irrigation, despite a high Lm prevalence in surface water suggesting other factors may play a role. Furthermore, Lm prevalence increased when the microbiome's Simpson's Diversity Index decreased, which occurred as soil fertility increased, leading to an indirect positive effect for soil fertility on Lm prevalence. These results suggest that pathogen, environment, and farm management practices, in addition to produce commodities, all need to be considered when developing mitigation strategies. The prevalence of Arcobacter and Lm versus the other pathogens suggests that multiple mitigation strategies may need to be employed to control these pathogens.

Use of a Unique Farmers' Market Program Targeting Lower-Income Community Members.

We examined use of a farmers' market that leverages community partnerships to provide free produce to lower-income persons. Participants (n = 422) were asked to complete a questionnaire and given an ID number, which was used to track market use from 2014 to 2015. Chi square tests were used to examine associations between 2014/2015 market use and reasons for market use, financial support received, and how attendees had learned about the market. Ordinal regression was used to identify household characteristics associated with increased market attendance. Although the proportion of lower-income attendees declined over the study period, a substantial proportion of households in 2014 (69.1%) and 2015 (54.6%) were below the poverty threshold. We identified significant differences in attendees' reasons for market use and ways attendees heard about the market from 2014 to 2015. The most frequently reported reason for 2014 market use was retirement/fixed income (P < 0.001) and in 2015 was low-income (P < 0.001). Most attendees heard about the market through flyers (P < 0.001) and word of mouth (P ≤ 0.001) in 2014 and through local, non-profit services (P < 0.001) in 2015. In the ordinal regression, households with an older person registering the household for the market used the market more times per year (P < 0.001). Impoverished households (P = 0.020) and households receiving more financial support services (P < 0.001) used the market fewer times per year. While a substantial proportion of lower-income persons used the free-produce market, frequency of use was still lowest among this group indicating a need to address barriers beyond produce cost.

Assessing Heavy Metal and PCB Exposure from Tap Water by Measuring Levels in Plasma from Sporadic Breast Cancer Patients, a Pilot Study.

Breast cancer (BrCA) is the most common cancer affecting women around the world. However, it does not arise from the same causative agent among all women. Genetic markers have been associated with heritable or familial breast cancers, which may or may not be confounded by environmental factors, whereas sporadic breast cancer cases are more likely attributable to environmental exposures. Approximately 85% of women diagnosed with BrCA have no family history of the disease. Given this overwhelming bias, more plausible etiologic mechanisms should be investigated to accurately assess a woman's risk of acquiring breast cancer. It is known that breast cancer risk is highly influenced by exogenous environmental cues altering cancer genes either by genotoxic mechanisms (DNA mutations) or otherwise. Risk assessment should comprehensively incorporate exposures to exogenous factors that are linked to a woman's individual susceptibility. However, the exact role that some environmental agents (EA) play in tumor formation and/or cancer gene regulation is unclear. In this pilot project, we begin a multi-disciplinary approach to investigate the intersection of environmental exposures, cancer gene response, and BrCA risk. Here, we present data that show environmental exposure to heavy metals and PCBs in drinking water, heavy metal presence in plasma of nine patients with sporadic BrCA, and Toxic Release Inventory and geological data for a metal of concern, uranium, in Northeast Georgia.

Maize seedling blight induced by Fusarium verticillioides: accumulation of fumonisin B1 in leaves without colonization of the leaves.

Fusarium verticillioides produces fumonisin mycotoxins during the colonization of maize, and fumonisin B1 (FB1) production is necessary for manifestation of maize seedling blight disease. The objective of this study was to address FB1 mobility and accumulation in seedlings to determine if proximal infection by F. verticillioides is necessary for FB1 accumulation. Taking advantage of an aconidial mutant known to have limited capability for seedling infection, tissue and soil samples were analyzed to compare wild-type F. verticillioides against the mutant. Inoculation with either strain caused accumulation of FB1 in the first and second leaves, but the mutants were unable to colonize aerial tissues. FB1, FB2, and FB3 were detected in the soil and seedling roots, but only FB1 was detected in the leaves of any treatment. These data suggest root infection by F. verticillioides is necessary for accumulation of FB1 in leaves, but the mechanism for accumulation does not require colonization of the leaf.

Transformation-mediated complementation of a FUM gene cluster deletion in Fusarium verticillioides restores both fumonisin production and pathogenicity on maize seedlings.

The filamentous ascomycete Fusarium verticillioides is a pathogen of maize and produces the fumonisin mycotoxins. However, a distinct population of F. verticillioides is pathogenic on banana and does not produce fumonisins. Fumonisin-producing strains from maize cause leaf lesions, developmental abnormalities, stunting, and sometimes death of maize seedlings, whereas fumonisin-nonproducing banana strains do not. A Southern analysis of banana strains did not detect genes in the fumonisin biosynthetic gene (FUM) cluster but did detect genes flanking the cluster. Nucleotide sequence analysis of the genomic region carrying the flanking genes revealed that the FUM cluster was absent in banana strains except for portions of FUM21 and FUM19, which are the terminal genes at each end of the cluster. Polymerase chain reaction analysis confirmed the absence of the cluster in all banana strains examined. Cotransformation of a banana strain with two overlapping cosmids, which together contain the entire FUM cluster, yielded fumonisin-producing transformants that were pathogenic on maize seedlings. Conversely, maize strains that possess the FUM cluster but do not produce fumonisins because of mutations in FUM1, a polyketide synthase gene, were not pathogenic on maize seedlings. Together, the data indicate that fumonisin production may have been lost by deletion of the FUM cluster in the banana population of F. verticillioides but that fumonisin production could be restored by molecular genetic complementation. The results also indicate that fumonisin production by F. verticillioides is required for development of foliar disease symptoms on maize seedlings.

Fumonisin disruption of ceramide biosynthesis in maize roots and the effects on plant development and Fusarium verticillioides-induced seedling disease.

The fungus Fusarium verticillioides infects maize and produces fumonisins, inhibitors of ceramide synthase. Seeds of the cultivar Silver Queen were inoculated with fumonisin-producing or non-fumonisin-producing strains of F. verticillioides. Leaf lesion incidence and severity of effects on root and stalk growth were significantly correlated with fumonisin in roots and disruption of sphingolipid metabolism in roots. Uninoculated seeds grown in soil watered with solutions of fumonisin B1 exhibited above-ground symptoms indicative of F. verticillioides-induced seedling disease and dose-dependent reduction in root mass that was inversely correlated with fumonisin B1, sphingoid bases, and sphingoid base 1-phosphates in roots. There was also evidence of an adaptive response to disrupted sphingolipid metabolism in both the virulence and watering assays, suggesting induction of pathways responsible for metabolism of sphingoid base 1-phosphates after prolonged exposure. The results suggest that fumonisin, and its effects on sphingolipids, could contribute to all aspects of F. verticillioides maize seedling disease.

The plant MT1 metallothioneins are stabilized by binding cadmiums and are required for cadmium tolerance and accumulation.

The small Arabidopsis genome contains nine metallothionein-like (MT) sequences with classic, cysteine-rich domains separated by spacer sequences, quite unlike the small conserved MT families found vertebrate genomes. Phylogenetic analysis revealed four ancient and divergent classes of plant MTs that predate the monocot-dicot divergence. A distinct cysteine spacing pattern suggested differential metal ion specificity for each class. The in vivo stability of representatives of the four classes of plant MT proteins and a mouse MT2 control expressed in E. coli were enhanced by cadmium (Cd). Particular MTs were also stabilized by arsenic (As), copper (Cu), and or zinc (Zn). To understand why plants have such a diversity of MT sequences, the Arabidopsis MT1 class, comprised of three genes, MT1a, MT1b, and MT1c, was characterized in more detail in plants. MT1 family transcripts were knocked down to less than 5-10% of wild-type levels in Arabidopsis by expression of a RNA interference (RNAi) construct. The MT1 knockdown plant lines were all hypersensitive to Cd and accumulated several fold lower levels of As, Cd, and Zn than wildtype, while Cu and Fe levels were unaffected. The ancient class of MT1 protein sequences may be preserved in plant genomes, because it has distinct metal-binding properties, confers tolerance to cadmium, and can assist with zinc homeostasis.