Interspecies killing activity of Pseudomonas syringae tailocins.

Tailocins are ribosomally synthesized bacteriocins, encoded by bacterial genomes, but originally derived from bacteriophage tails. As with both bacteriocins and phage, tailocins are largely thought to be species-specific with killing activity often assumed to be directed against closely related strains. Previous investigations into interactions between tailocin host range and sensitivity across phylogenetically diverse isolates of the phytopathogen Pseudomonas syringae have demonstrated that many strains possess intraspecific tailocin activity and that this activity is highly precise and specific against subsets of strains. However, here we demonstrate that at least one strain of P. syringae, USA011R, defies both expectations and current overarching dogma because tailocins from this strain possess broad killing activity against other agriculturally significant phytopathogens such as Erwinia amylovora and Xanthomonas perforans as well as against the clinical human pathogen Salmonella enterica serovar Choleraesuis. Moreover, we show that the full spectrum of this interspecific killing activity is not conserved across closely related strains with data suggesting that even if tailocins can target different species, they do so with different efficiencies. Our results reported herein highlight the potential for and phenotypic divergence of interspecific killing activity of P. syringae tailocins and establish a platform for further investigations into the evolution of tailocin host range and strain specificity.

Variations in Bacterial Communities and Antibiotic Resistance Genes Across Diverse Recycled and Surface Water Irrigation Sources in the Mid-Atlantic and Southwest United States: A CONSERVE Two-Year Field Study.

Reduced availability of agricultural water has spurred increased interest in using recycled irrigation water for U.S. food crop production. However, there are significant knowledge gaps concerning the microbiological quality of these water sources. To address these gaps, we used 16S rRNA gene and metagenomic sequencing to characterize taxonomic and functional variations (e.g., antimicrobial resistance) in bacterial communities across diverse recycled and surface water irrigation sources. We collected 1 L water samples (n = 410) between 2016 and 2018 from the Mid-Atlantic (12 sites) and Southwest (10 sites) U.S. Samples were filtered, and DNA was extracted. The V3-V4 regions of the 16S rRNA gene were then PCR amplified and sequenced. Metagenomic sequencing was also performed to characterize antibiotic, metal, and biocide resistance genes. Bacterial alpha and beta diversities were significantly different (p < 0.001) across water types and seasons. Pathogenic bacteria, such as Salmonella enterica, Staphylococcus aureus, and Aeromonas hydrophilia were observed across sample types. The most common antibiotic resistance genes identified coded against macrolides/lincosamides/streptogramins, aminoglycosides, rifampin and elfamycins, and their read counts fluctuated across seasons. We also observed multi-metal and multi-biocide resistance across all water types. To our knowledge, this is the most comprehensive longitudinal study to date of U.S. recycled water and surface water used for irrigation. Our findings improve understanding of the potential differences in the risk of exposure to bacterial pathogens and antibiotic resistance genes originating from diverse irrigation water sources across seasons and U.S. regions.

Plant-based antimicrobials inactivate Listeria monocytogenes and Salmonella enterica on melons grown in different regions of the United States.

The efficacy of plant-based antimicrobials against Salmonella Newport and Listeria monocytogenes on melon rinds was evaluated. Four cantaloupe and 3 honeydew melon varieties grown in Georgia, Arizona, Texas, North Carolina, Indiana and California were tested. Melon rinds (10 g pieces) were inoculated with 5-6 log CFU/10 g rind of S. Newport or L. monocytogenes. Samples were then immersed in 5 % olive extract or 0.5 % oregano oil antimicrobial solution and gently agitated for 2 min. Samples were stored at 4 °C and surviving populations of both bacteria were enumerated at days 0 and 3. Plant-based antimicrobials reduced S. Newport and L.monocytogenes population on all rind samples, regardless of the melon types, varieties or growing locations. Compared to the control, antimicrobial treatments caused up to 3.6 and 4.0 log reductions in populations of Salmonella and L. monocytogenes, respectively. In most cases, plant-based antimicrobial treatments reduced pathogen populations to below the detection limit (1 log CFU/g) at day 3. In general, oregano oil had better antimicrobial activity than olive extract and the antimicrobial treatments were more effective on Salmonella than on L. monocytogenes. The plant-based antimicrobial treatments exhibited better microbial reductions on honeydews than on cantaloupes. These antimicrobials could potentially be used as sanitizers for decontaminating melons.

Essential Oil Microemulsions Inactivate Antibiotic-Resistant Bacteria on Iceberg Lettuce during 28-Day Storage at 4 °C.

The objective of this study was to investigate the antimicrobial activities of essential oil-based microemulsions in the wash water against Escherichia coli O157:H7 and Pseudomonas fluorescens on Iceberg lettuce. Evaluated wash microemulsions included oregano oil, lemongrass oil, and cinnamon oil, along with a plant-based emulsifier for improved solubility. Iceberg lettuce was inoculated for 2 min with E. coli O157:H7 (6.0 log CFU/g) or P. fluorescens (6.0 log CFU/g) and then dip-treated in a phosphate buffered saline (PBS) control, 50 ppm chlorine, 3% hydrogen peroxide treatment or a 0.1%, 0.3%, or 0.5% microemulsion solution. Treated leaves were stored at 4 °C, and analyzed for surviving bacteria on days 0, 3, 7, 10, 14, 21, and 28. Efficacies of the antimicrobials were concentration and storage-time dependent. There was a 1.26−4.86 log CFU/g reduction in E. coli O157:H7 and significant reductions (0.32−2.35 log CFU/g) in P. fluorescens during storage at days 0−28 (p < 0.05). The 0.1% oregano oil microemulsion resulted in the best visual appeal in Iceberg leaves inoculated with E. coli O157:H7 and showed better improvement in the quality of the Iceberg leaves inoculated with spoilage bacteria P. fluorescens. The results suggest that 0.5% cinnamon and 0.3% oregano oil treatments have the potential to provide natural, eco-friendly, and effective alternatives to chemicals for the decontamination of leafy greens, eliminating E. coli O157:H7 and P. fluorescens.

Ozonized water with plant antimicrobials: An effective method to inactivate Salmonella enterica on iceberg lettuce in the produce wash water.

Post-harvest washing of produce is performed to remove physical debris and to lower microbial load. The use of ozone in combination with plant-based antimicrobials was evaluated as an alternative to conventional sanitizers such as chlorine. Plant based antimicrobials that were evaluated in combination with ozone included oregano oil, carvacrol, Quillaja saponin and olive extract. Ozone was dispersed in phosphate buffered saline (PBS), following which individual antimicrobials or their combinations were added. Iceberg lettuce leaves (10 g portions) inoculated with Salmonella enterica serotype Newport (6.5 ±â€¯1 log CFU/g) were added to the wash suspension. The leaves were tested for reduction in S. Newport population after 60, 90 and 120 min of treatment. Exposure to ozonized water for 120 min resulted in a 2.1 log CFU/g (p < 0.05) reduction in S. Newport population. The addition of 0.1% oregano oil to ozonized water resulted in 3 log CFU/g reduction after 120 min but a 4.1 log CFU/g reduction after 60 min, indicating that the antioxidant property of oregano oil might have diminished ozone activity and resuscitated injured S. Newport cells. The addition of 5% olive extract to ozonized water resulted in 4.2 log CFU/g reduction of S. Newport after 120 min (p < 0.05) of treatment. While 5% olive extract did not confer protection to S. Newport cells from ozone, 1% olive extract resulted in higher S. Newport survival after 120 min treatment than the 60 min treatment. The use of carvacrol (0.1%, 0.3% and 0.5%) in ozonized water reduced the pathogen population to below the limit of detection (10 CFU/g) (p < 0.05) which was in excess of 6 log CFU/g. These results indicate that the efficacy of ozone is compounded by the addition of certain plant-based antimicrobials when used at optimum concentrations. Ozone combined with plant antimicrobials could serve as an effective alternative to sanitizers currently used for washing and processing of produce.

Incidence of fecal indicator and pathogenic bacteria in reclaimed and return flow waters in Arizona, USA.

The quality of irrigation water used to cultivate produce that is consumed raw is an important issue with regard to food safety. In this study, the microbiological quality of potential irrigation water sources in Arizona was evaluated by testing for the presence of indicator and pathogenic bacteria. Reclaimed water samples were collected from two wastewater treatment plants and return flow samples were collected from two drainage canals and one return flow pond. Standard membrane filtration methods were used for detection of indicator bacteria. Water samples (n = 28) were filtered through cellulose ester membrane filters and bacterial populations were enumerated by placing the filters on selective agar. For detection of pathogens (Salmonella enterica, Listeria monocytogenes and Shiga toxin-producing E. coli (STEC)), water samples were filtered through Modified Moore swabs and enriched in Universal Pre-enrichment Broth, followed by selective enrichment broth for each pathogen. The enriched broth was streaked onto agar media selective for each pathogen. Presumptive colonies were confirmed by PCR/real-time PCR. Among the 14 reclaimed water samples from two sites, the ranges of recovered populations of E. coli, total coliforms, and enterococci were 0-1.3, 0.5-8.3 × 103, and 0-5.5 CFU/100 mL, respectively. No L. monocytogenes, Salmonella or STEC were found. In the 13 return flow water samples from 3 sites, the ranges of recovered populations of E. coli, total coliforms and enterococci were 1.9-5.3 × 102, 6.5 × 102-9.1 × 104, and 2.9-3.7× 103 CFU/100 mL, respectively. All samples were negative for L. monocytogenes. One (7.1%) of the return flow samples was positive for E. coli O145. Nine (64.3%) of the samples were positive for Salmonella. Both real-time PCR and culture-based methods were used for the detection of Salmonella and L. monocytogenes, and the results from the two methods were comparable. The findings of this study provide evidence that irrigation waters in Arizona, including reclaimed water and return flows, could be potential sources of bacterial contamination of produce. Additional work is needed to evaluate whether bacteria present in irrigation water sources transfer to the edible portion of irrigated plants and are capable of persisting through post-harvest activities.

Pharmaceuticals, herbicides, and disinfectants in agricultural water sources.

Agricultural water withdrawals account for the largest proportion of global freshwater use. Increasing municipal water demands and droughts are straining agricultural water supplies. Therefore, alternative solutions to agricultural water crises are urgently needed, including the use of nontraditional water sources such as advanced treated wastewater or reclaimed water, brackish water, return flows, and effluent from produce processing facilities. However, it is critical to ensure that such usage does not compromise soil, crop, and public health. Here, we characterized five different nontraditional water types (n = 357 samples) for the presence of pharmaceuticals, herbicides, and disinfectants using ultra-high-pressure liquid chromatography tandem mass spectrometry based method (UPLC-MS/MS). We then evaluated whether the levels of these contaminants were influenced by season. The highest level of herbicides (atrazine) was detected in untreated pond water (median concentration 135.9 ng/L). Reclaimed water had the highest levels of antibiotics and stimulants including azithromycin (215 ng/L), sulfamethoxazole (232.1 ng/L), and caffeine (89.4 ng/L). Produce processing plant water also tended to have high levels of atrazine (102.7 ng/L) and ciprofloxacin (80.1 ng/L). In addition, we observed seasonal variability across water types, with the highest atrazine concentrations observed during summer months, while the highest median azithromycin concentrations were observed in reclaimed water during the winter season. Further studies are needed to evaluate if economically feasible on-farm water treatment technologies can effectively remove such contaminants from nontraditional irrigation water sources.

Antimicrobial efficacy of plant essential oils and extracts against Escherichia coli.

The efficacies of 11 plant-derived antimicrobials were evaluated against Escherichia coli in vitro in solution at room temperature. These included lemongrass, cinnamon, and oregano essential oils and their active components (citral, cinnamaldehyde, and carvacrol, respectively). Allspice and clove bud oils and olive, green tea, and grape seed extracts were also studied. The efficacies of the antimicrobials were both concentration- and exposure time-dependent. The essential oils and their active components demonstrated statistically significant >5.0-log10 reductions within 1-10 min. The plant extracts were less effective; green tea and grape seed extracts required 24 h before significant reductions were observed (1.93-log10 and 5.05-log10, respectively). Nevertheless, olive extract exhibited a reduction of ∼5-log10 within 30 min. Most of these plant-derived compounds exhibited strong bactericidal activity and can potentially be applied as alternatives to chemicals for foods/food contact surfaces since they are generally recognized as safe (GRAS) for human consumption. They may also be useful in applications in which other antimicrobials have reduced efficacy (e.g., in the presence of organics) or used with sensitive populations that are unable to tolerate exposure to harsher chemicals (e.g., elderly care facilities). These compounds could be used alone, in combination, or with fast-acting antimicrobials to provide a long-lasting residual.

Bacterial diversity and composition on the rinds of specific melon cultivars and hybrids from across different growing regions in the United States.

The goal of this study was to characterize the bacterial diversity on different melon varieties grown in different regions of the US, and determine the influence that region, rind netting, and variety of melon has on the composition of the melon microbiome. Assessing the bacterial diversity of the microbiome on the melon rind can identify antagonistic and protagonistic bacteria for foodborne pathogens and spoilage organisms to improve melon safety, prolong shelf-life, and/or improve overall plant health. Bacterial community composition of melons (n = 603) grown in seven locations over a four-year period were used for 16S rRNA gene amplicon sequencing and analysis to identify bacterial diversity and constituents. Statistically significant differences in alpha diversity based on the rind netting and growing region (p < 0.01) were found among the melon samples. Principal Coordinate Analysis based on the Bray-Curtis dissimilarity distance matrix found that the melon bacterial communities clustered more by region rather than melon variety (R2 value: 0.09 & R2 value: 0.02 respectively). Taxonomic profiling among the growing regions found Enterobacteriaceae, Bacillaceae, Microbacteriaceae, and Pseudomonadaceae present on the different melon rinds at an abundance of ≥ 0.1%, but no specific core microbiome was found for netted melons. However, a core of Pseudomonadaceae, Bacillaceae, and Exiguobacteraceae were found for non-netted melons. The results of this study indicate that bacterial diversity is driven more by the region that the melons were grown in compared to rind netting or melon type. Establishing the foundation for regional differences could improve melon safety, shelf-life, and quality as well as the consumers' health.

Antimicrobial activity of oregano oil against antibiotic-resistant Salmonella enterica on organic leafy greens at varying exposure times and storage temperatures.

The objective of this study was to evaluate the effectiveness of oregano oil on four organic leafy greens (Iceberg and Romaine lettuces and mature and baby spinaches) inoculated with Salmonella Newport as a function of treatment exposure times as well as storage temperatures. Leaf samples were washed, dip inoculated with S. Newport (6-log CFU/ml) and dried. Oregano oil was prepared at 0.1, 0.3, and 0.5% concentrations in sterile phosphate buffered saline (PBS). Inoculated leaves were immersed in the treatment solution for 1 or 2 min, and individually incubated at 4 or 8 °C. Samples were taken at day 0, 1, and 3 for enumeration of survivors. The results showed that oregano oil was effective against S. Newport at all concentrations. S. Newport showed reductions from the PBS control of 0.7-4.8 log CFU/g (Romaine lettuce), 0.8-4.8 log CFU/g (Iceberg lettuce), 0.8-4.9 log CFU/g (mature spinach), and 0.5-4.7 log CFU/g (baby spinach), respectively. The antibacterial activity also increased with exposure time. Leaf samples treated for 2 min generally showed greater reductions (by 1.4-3.2 log CFU/g), than those samples treated for 1 min; however, there was minimal difference in antimicrobial activity among samples stored under refrigeration and abuse temperatures. This study demonstrates the potential of oregano oil to inactivate S. Newport on organic leafy greens.

Antimicrobial activity of plant essential oils against Escherichia coli O157:H7 and Salmonella on lettuce.

Foodborne outbreaks associated with the consumption of fresh produce have increased. In an effort to identify natural antimicrobial agents as fresh produce-wash, the effect of essential oils in reducing enteric pathogens on iceberg and romaine lettuce was investigated. Lettuce pieces were inoculated with a five-strain cocktail of Escherichia coli O157:H7 or Salmonella enterica (5 log CFU/g) and then immersed in a treatment solution containing 5 ppm free chlorine, cinnamaldehyde, or Sporan(®) (800 and 1000 ppm) alone or in combination with 200 ppm acetic acid (20%) for 1 min. Treated leaves were spin-dried and stored at 4°C. Samples were taken to determine the surviving populations of E. coli O157:H7, Salmonella, total coliforms, mesophilic and psychrotrophic bacteria, and yeasts and molds during the 14-day storage period. The effect of treatments on lettuce color and texture was also determined. Cinnamaldehyde-Tween (800 ppm, 800T) reduced E. coli O157:H7 by 2.89 log CFU/g (p<0.05) on iceberg lettuce at day 0; Sporan(®)-acetic acid (1000SV) reduced E. coli O157:H7 and Salmonella on iceberg and romaine lettuce by 2.68 and 1.56 log CFU/g (p<0.05), respectively, at day 0. The effect of essential oils was comparable to that of 5 ppm free chlorine in reducing E. coli O157:H7 and Salmonella populations on iceberg and romaine lettuce throughout the storage time. The natural microbiota on treated lettuce leaves increased during the storage time, but remained similar (p>0.05) to those treated with chlorine and control (water). The texture and the color of iceberg and romaine lettuce treated with essential oils were not different from the control lettuce after 14 days of storage. This study demonstrates the potential of Sporan(®) and cinnamaldehyde as effective lettuce washes that do not affect lettuce color and texture.

Antimicrobial activity of different copper alloy surfaces against copper resistant and sensitive Salmonella enterica.

Copper has shown antibacterial effects against foodborne pathogens. The objective of this study was to evaluate the antibacterial activity of copper surfaces on copper resistant and sensitive strains of Salmonella enterica. Six different copper alloy coupons (60-99.9% copper) were tested along with stainless steel as the control. The coupons were surface inoculated with either S. Enteritidis or one of the 3 copper resistant strains, S. Typhimurium S9, S19 and S20; stored under various incubation conditions at room temperature; and sampled at various times up to 2 h. The results showed that under dry incubation conditions, Salmonella only survived 10-15 min on high copper content alloys. Salmonella on low copper content alloys showed 3-4 log reductions. Under moist incubation conditions, no survivors were detected after 30 min-2 h on high copper content alloys, while the cell counts decreased 2-4 logs on low copper content coupons. Although the copper resistant strains survived better than S. Enteritidis, they were either completely inactivated or survival was decreased. Copper coupons showed better antimicrobial efficacy in the absence of organic compounds. These results clearly show the antibacterial effects of copper and its potential as an alternative to stainless steel for selected food contact surfaces.

Effects and interactions of sodium lactate, sodium diacetate, and pediocin on the thermal inactivation of starved Listeria monocytogenes on bologna.

The effects and interactions of temperature (56.3-60 °C), sodium lactate (SL; 0-4.8%), sodium diacetate (SDA; 0-2.5%), and pediocin (0-10,000 AU) on starved Listeria monocytogenes (10(7) CFU/g) on bologna were investigated. Bologna slices containing SL and SDA in the formulation were dipped in pediocin, surface inoculated, and treated at various temperatures using combinations of parameters determined by central composite design. D-values were calculated. The observed D-values ranged from 2.8 min at 60 °C to 24.61 min at 56.3 °C. Injury ranged from 9.1 to 76% under various conditions. The observed D-values were analyzed using second order response surface regression for temperature, SL, SDA, and pediocin, and a predictive model was developed. Predicted D-values were calculated and ranged from 3.7 to 19 min for various combinations of parameters. Temperature alone reduced the predicted D-values from 33.96 min at 56.3 °C to 11.51 min at 60 °C. Addition of SL showed a protective effect. Other combination treatments either reduced or increased D-values depending on temperature. The combination of SL and SDA was effective at lower temperatures, however, higher levels of SDA at higher temperatures made the organism more heat resistant. Pediocin (up to 5000 AU) with increasing temperature and SDA reduced D-values. Depending on temperature and concentration, the interactions between various additives can affect thermal inactivation of L. monocytogenes on bologna. Starvation rendered L. monocytogenes more susceptible to heat and additives.

Carvacrol and cinnamaldehyde inactivate antibiotic-resistant Salmonella enterica in buffer and on celery and oysters.

The emergence of antibiotic-resistant Salmonella is of concern to food processors. The objective of this research was to identify antimicrobial activities of cinnamaldehyde and carvacrol against antibiotic-resistant Salmonella enterica in phosphate-buffered saline (PBS) and on celery and oysters. Twenty-three isolates were screened for resistance to seven antibiotics. Two resistant and two susceptible strains were chosen for the study. S. enterica cultures (10(5) CFU/ml) were added to different concentrations of cinnamaldehyde and carvacrol (0.1, 0.2, 0.3, and 0.4% [vol/vol]) in PBS, mixed, and incubated at 37 degrees C. Samples were taken at 0, 1, 5, and 24 h for enumeration. Celery and oysters were inoculated with S. enterica (10(6-7) CFU/ml), treated with 1% cinnamaldehyde or 1% carvacrol, incubated at 4 degrees C, and then sampled for enumeration on days 0 and 3. Both antimicrobials induced complete inactivation of S. enterica in PBS at 0.3 and 0.4% on exposure, and on 0.2% in 1 h. Exposure to cinnamaldehyde at 0.1% inactivated all pathogens at 1 h, and survivors were observed only for Salmonella Newport with 0.1% carvacrol at 1 h. In celery, 1% carvacrol reduced S. enterica populations to below detection on day 0, while 1% cinnamaldehyde reduced populations by 1 and 2.3 log on day 0 and day 3, respectively. In oysters, both antimicrobials caused about 5-log reductions on day 3. These results show the potential antimicrobial effects of carvacrol and cinnamaldehyde against antibiotic-resistant S. enterica in vitro and in foods.

Assessing the cross contamination and transfer rates of Salmonella enterica from chicken to lettuce under different food-handling scenarios.

Cross contamination of foodborne pathogens from raw meats to ready-to-eat foods has caused a number of foodborne outbreaks. The cross contamination and transfer rates of Salmonella enterica from chicken to lettuce under various food-handling scenarios were determined. The following scenarios were tested: in scenario 1, cutting board and knife used to cut chicken (10(6) CFU/g) were also used for cutting lettuce, without washing; in scenario 2, cutting board and knife were washed with water separately after cutting chicken, and subsequently used for cutting lettuce; and in scenario 3, cutting board and knife were thoroughly washed with soap and hot water after cutting chicken, and before cutting lettuce. In each scenario, cutting board, knife, chicken and lettuce were sampled for population of S. enterica. For scenario 1, both before and after cutting lettuce, the cutting board and knife each had about 2 logs CFU/cm(2) of S. enterica, respectively. The cut lettuce had about 3 logs CFU/g of S. enterica. In scenario 2, fewer organisms (0.5-2.4 logs CFU/g or cm(2)) were transferred. The transfer rates in both scenarios ranged from 0.02 to 75%. However, in scenario 3, <1 log CFU/g or cm(2) organisms were detected on lettuce, cutting board or knife, after washing and cutting lettuce. This shows that the FDA recommended practice for cleaning cutting boards is effective in removing S. enterica and preventing cross contamination.

Sodium lactate, sodium diacetate and pediocin: Effects and interactions on the thermal inactivation of Listeria monocytogenes on bologna.

The effects and interactions of temperature (56.3-60 degrees C), sodium lactate (SL; 0-4.8%), sodium diacetate (SD; 0-0.25%) and pediocin (0-10,000 AU) on Listeria monocytogenes on bologna were studied and a predictive inactivation model was developed. Bologna was manufactured with different SL/SD concentrations in the formulation, dipped in pediocin solution and treated at different temperatures using combinations of parameters determined by central composite design. D-values were calculated and analyzed using second order response regression. Predicted D-values were also calculated. The observed D-values for L. monocytogenes on bologna ranged from 2.10 to 35.59 min. Temperature alone decreased predicted D-values from 99.02 min at 56.3 degrees C to 44.71 min at 60.0 degrees C. Adding SL decreased D-values (85.43-22.71 min) further; however, heat and SD combined was the most effective for reducing L. monocytogenes on bologna. An SD level of 0.25% at 58.2 degrees C had the overall lowest predicted D-value (15.95 min). Combination treatments increased or decreased D-values, depending on the temperature. Pediocin (2500 and 5000 AU) and heat decreased D-values, but exhibited a protective effect at higher concentrations (>or=7500 AU). The results showed that interactions between additives in formulations can vary at different temperatures/concentrations, thereby affecting thermal inactivation of foodborne pathogens in meat products. Hence, food processors should modify food formulations carefully, and verify with adequate testing so that product safety is not compromised.

Contamination of spinach at germination: A route to persistence and environmental reintroduction by Salmonella.

The effects of using contaminated seed and water on the persistence and internalization of Salmonella Newport in organic spinach cultivars- Lazio, Space, Emilia and Waitiki were studied. Seeds were contaminated by either immersing in a suspension of Salmonella and then sprouted or were sprouted in Salmonella contaminated water in the dark at 25 °C. After 5 days, germinated sprouts were analyzed for S. Newport population and internalization. Germinated sprouts were potted in soil and grown in a plant incubator for 4 weeks. Leaves, stems and roots were sampled for Salmonella population by plating on CHROMagar™. Plants surface-sterilized with chlorine were analyzed for internalized pathogen. Potting soil and water runoff were sampled for Salmonella after 4 weeks of plant growth. Contaminated seeds and irrigation water had S. Newport populations of 7.64±0.43 log CFU/g and 7.12±0.04 log CFU/ml, respectively. Sprouts germinated using contaminated water or seeds had S. Newport populations of 8.09±0.04 and 8.08±0.03 log CFU/g, respectively and had a Salmonella population that was significantly higher than other spinach tissues (P<0.05). Populations of S. Newport in leaves, stem and roots of spinach plants were as follows: contaminated seed- 2.82±1.69, 1.69±0.86, and 4.41±0.62 log CFU/ml; contaminated water- 3.56±0.90, 3.04±0.31, and 4.03±0.42 log CFU/ml of macerated tissue suspension, respectively. Internalization was observed in plants developing from contaminated seeds and in sprouts germinated using contaminated water. S. Newport populations of 2.82±0.70 log CFU/g and 1.76±0.46 log CFU/ml were recovered from soil and water runoff, respectively. The results indicate that contamination of spinach during germination can result in persistence, internalization and environmental reintroduction of Salmonella.

Assessing the Food Safety Risk Posed by Birds Entering Leafy Greens Fields in the US Southwest.

In the US Southwest, it is common to observe birds in leafy green fields, though the risk they contribute to foodborne outbreaks remains unclear. In this study, we investigated and recorded the relationship between birds near leafy green fields and the risk for contaminated irrigation water or leafy green plants. We monitored the presence of birds for over two years and performed cloacal swab analysis for non-pathogenic Escherichia coli, E. coli O157:H7 and Salmonellaenterica, while also monitoring the incidence of other microbial indicators. We also assessed the risks from bird feces by performing observations in a commercial field reported with Salmonella positive samples and by analyzing the survival of foodborne pathogens in bird feces. Our results showed that most of the birds near the crop fields were resident small birds. We did not observe a correlation between the number of birds in sites and the incidence of indicator bacteria (e.g., coliforms, E. coli) in irrigation canal water, with the exception of one out of four sites where water flow was low or stagnant. Using walk-in-traps, 305 birds were captured and placed in short-term captivity to determine the presence of various bacteria. None of the birds tested positive for E. coli O157:H7 or Salmonella. However, nearly 40% of the birds captured were confirmed positive for non-pathogenic E. coli. We found no correlation between age (young, adult, unknown), gender (male, female, unknown) and the incidence of E. coli positive birds, but we observed significantly higher probability of incidence during October-December. The role of relative humidity and temperature on bacterial survival appeared to play a key role in the survival of Salmonella on the leaves of spinach plants in a commercial field. This was also confirmed in laboratory conditions where Salmonella inoculated in bird feces and exposed to 15 °C and 80% RH(Relative humidity) survived beyond 133 days, while at 26 °C and 40% RH, the organism was undetectable after 63 days. Our results suggest that local birds associated with leafy green fields likely pose a minimal impact of risk for food contamination, but also points out the need for increased analysis specifically for E. coli O157:H7. Furthermore, our study suggests the need for expanding research that addresses risks associated with large migratory birds, especially in areas where stagnated water sources would be used for overhead sprinkle irrigation.

Assessment of antioxidant and antidiabetic properties of Agaricus blazei Murill extracts.

Agaricus blazei Murill (ABM), a medicinal mushroom, has beneficial effects on various human metabolic diseases. The objective of this research was to evaluate the antioxidant and antidiabetic properties of ABM extracts (ethanol extract and ethyl acetate extract). The antioxidant activities of ABM ethanol extract (EE) and ethyl acetate extract (EA) were analyzed using 1,1-diphenyl-2-picrylhydrazyl (DPPH), 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS), and hydroxyl radical scavenging assays and the reducing power using K3Fe(CN)6 in vitro. Moreover, the effects of EE and EA on α-glucosidase inhibitory activity and improving glucose uptake by HepG2 cells were investigated in vitro. The EA showed stronger antioxidant activity, as well as inhibition of α-glucosidase, compared to EE. The analysis of glucose uptake by HepG2 cells showed that EA had significant glucose-lowering activity and exhibited no difference compared to metformin. The results suggest that ABM extracts could improve the glucose uptake by HepG2 cells and thereby alleviate postprandial hyperglycemia. This investigation provides a strong rationale for further studies on the application of ABM to control type 2 diabetes.

Multivariate Analysis of Amino Acids and Health Beneficial Properties of Cantaloupe Varieties Grown in Six Locations in the United States.

Cantaloupe is a good dietary source of amino acids, including γ-aminobutyric acid (GABA), glutamine, and citrulline. However, the levels of these amino acids vary among different cantaloupe varieties grown in different locations. Understanding the variation in amino acid contents provides fundamentally important information for quality control and improving melon varieties. To examine this variation, we measured the amino acid contents in cantaloupes grown in six locations in the United States (Texas, Georgia, North Carolina, California, Indiana, and Arizona). Principal component analyses were applied to analyze the effect of growing location on the amino acid profiles in different varieties. The GABA content ranged from 1006.14 ± 64.77 to 3187.12 ± 64.96 µg/g and citrulline ranged from 92.65 ± 9.52 to 464.75 ± 34.97 µg/g depending on the variety and location. Total phenolic contents, α-amylase inhibition, and antioxidant activities were also measured. Tuscan type Da Vinci had significantly higher phenolic contents in Arizona (381.99 ± 16.21 µg/g) but had the lowest level when grown in California (224.56 ± 14.62 µg/g). Our analyses showed significant differences in amino acid levels, phenolics contents, and antioxidant activity in the cantaloupe varieties based on the growing location. These findings underline the importance of considering growing location in the selection and improvement of cantaloupe varieties.