Fawzy Hashem

Survival and Growth of Listeria monocytogenes in Broth as a Function of Temperature, pH, and Potassium Lactate and Sodium Diacetate Concentrations

The objective of this study was to determine the antimicrobial effect of a combination of potassium lactate and sodium diacetate (0, 1.8, 3, and 4.5%; PURASAL P Opti. Form 4, 60% solution) on the survival and growth of Listeria monocytogenes Scott A in pH-adjusted broth (5.5, 6.0, 6.5, and 7.0) stored at 4, 10, 17, 24, 30, and 37 degrees C. Appropriate dilutions of broth were enumerated by spiral plating on tryptose agar and counted with an automated colony counter. Growth data were iteratively fit, using nonlinear regression analysis to a three-phase linear model, using GraphPad PRISM. At pH 5.5, the combination of lactate-diacetate fully inhibited (P < 0.001) the growth of L. monocytogenes at all four levels and six temperatures. At pH 6.0, addition of 1.8% lactate-diacetate reduced (P < 0.001) the specific growth rate of L. monocytogenes and increased lag time; however, 3 and 4.5% completely inhibited the growth at the six temperatures studied. Efficacy of the lactate-diacetate mixture was decreased as pH increased and incubation temperature increased. Thus, at pH 6.5, at least 3% was required to retard (P < 0.001) the growth of L. monocytogenes in broth. There was a limited effect of the lactate-diacetate level on the specific growth rate of the pathogen at pH 7.0. However, 1.8 and 3% significantly lengthened the lag time at 4 and 10 degrees C. These results suggest that 1.8% of lactate-diacetate mixture can be used as a substantial hurdle to the growth of L. monocytogenes when refrigerated temperatures are maintained for products with pH less than 6.5.

Salmonella and Campylobacter: Antimicrobial resistance and bacteriophage control in poultry

Salmonella and Campylobacter are major causes of foodborne related illness and are traditionally associated with consuming undercooked poultry and/or consuming products that have been cross contaminated with raw poultry. Many of the isolated Salmonella and Campylobacter that can cause disease have displayed antimicrobial resistance phenotypes. Although poultry producers have reduced on-the-farm overuse of antimicrobials, antimicrobial resistant Salmonella and Campylobacter strains still persist. One method of bio-control, that is producing promising results, is the use of lytic bacteriophages. This review will highlight the current emergence and persistence of antimicrobial resistant Salmonella and Campylobacter recovered from poultry as well as bacteriophage research interventions and limitations.

Microbiological quality of fresh produce obtained from retail stores on the Eastern Shore of Maryland, United States of America.

The aim of this study was to investigate the microbiological quality of six types of fresh produce obtained from three retail stores located on the Eastern Shore of Maryland, USA. A total of 414 samples representing basil, cilantro, lettuce, scallion, spinach, and parsley were analyzed for total aerobic bacteria (APC), total coliforms, Escherichia coli, and three pathogenic bacteria (E. coli O157:H7, Listeria monocytogenes, and Salmonella), using standard methods. Presumptive pathogenic isolates were confirmed using BAX Polymerase Chain Reaction. Total aerobic populations varied widely between samples, while 38.41% were positive for total coliforms and only 10.15% for E. coli. Median abundance (log CFU/g) of total coliforms and E. coli were less than the limit of detection and that of APC ranged from 5.78 to 6.61 over the six produce types. There was a statistically significant difference in prevalence of total coliforms among the retail stores, but not for abundance of APC or prevalence of E. coli. E. coli O157:H7 and L. monocytogenes were detected in one spinach sample each, while one parsley and one cilantro sample were positive for Salmonella. There were no statistically significant differences in microbiological quality among produce types. Although the results of this study provided some indices of sanitary and/or spoilage level, no relationship was observed among the total aerobic bacteria, total coliforms, E. coli, and the presence of pathogenic bacteria in the samples tested.

A protocol for conducting rainfall simulation to study soil runoff.

Rainfall is a driving force for the transport of environmental contaminants from agricultural soils to surficial water bodies via surface runoff. The objective of this study was to characterize the effects of antecedent soil moisture content on the fate and transport of surface applied commercial urea, a common form of nitrogen (N) fertilizer, following a rainfall event that occurs within 24 hr after fertilizer application. Although urea is assumed to be readily hydrolyzed to ammonium and therefore not often available for transport, recent studies suggest that urea can be transported from agricultural soils to coastal waters where it is implicated in harmful algal blooms. A rainfall simulator was used to apply a consistent rate of uniform rainfall across packed soil boxes that had been prewetted to different soil moisture contents. By controlling rainfall and soil physical characteristics, the effects of antecedent soil moisture on urea loss were isolated. Wetter soils exhibited shorter time from rainfall initiation to runoff initiation, greater total volume of runoff, higher urea concentrations in runoff, and greater mass loadings of urea in runoff. These results also demonstrate the importance of controlling for antecedent soil moisture content in studies designed to isolate other variables, such as soil physical or chemical characteristics, slope, soil cover, management, or rainfall characteristics. Because rainfall simulators are designed to deliver raindrops of similar size and velocity as natural rainfall, studies conducted under a standardized protocol can yield valuable data that, in turn, can be used to develop models for predicting the fate and transport of pollutants in runoff.

Transport of dissolved trace elements in surface runoff and leachate from a Coastal Plain soil after poultry litter application

The application of poultry (Gallus gallus domesticus) litter to agricultural soils may exacerbate losses of trace elements in runoff water, an emerging concern to water quality. We evaluated trace elements (arsenic [As], mercury [Hg], selenium [Se], and zinc [Zn]) in surface runoff and leachate from an agricultural soil with and without poultry litter application. Litter from a commercial operation was applied by three methods—broadcast application, subsurface placement, and broadcast application followed by disking—to no-till soils with a history of receiving litter. Soil monolith lysimeters (61 by 61 by 61 cm)(24 by 24 by 24 in) were extracted from each of the treatments and subjected to rainfall simulation (1 hour, 61 mm h−1 [2.4 in hr−1]) 15 and 42 days after litter application. Broadcasting poultry litter significantly increased concentrations (mg L−1) and loads (g ha−1) of As and Zn in runoff during the first event relative to other application methods. Notably, incorporating litter, either by disking after broadcasting or by subsurface placement, lowered As and Zn in runoff to near background levels by the second event, and there were no significant differences in As and Zn between any of the treatments. While Hg and Se were detected in runoff, they likely derived from edaphic sources as they were not detected in the litter nor did they differ significantly between treatments. Results point to poultry litter as a temporary source of some trace elements to runoff. This source can be readily controlled by adjusting application method.

Effect of Insecticide Spray Applications, Sowing Dates and Cultivar Resistance on Insect Pests of Cowpea in the Delmarva Region of the United States

ABSTRACT Field studies were conducted to determine the effect of insecticide spray applications, sowing dates and cultivar resistance in diverse cowpea genotypes in the Delmarva (Delaware, Maryland and Virginia) peninsula region of the United States. A mixture of cypermethrin and dimethoate was applied in the first experiment and the number of spray applications ranged from two to six. The second experiment had two sowing date treatments and received four spray applications of endosulfan. Also, ten genotypes of cowpea were planted and observations were taken on the incidence of major insect pests and pod damage. There was a 30% increase in cowpea seed yield as a result of spraying the mixture of cypermethrin + dimethoate insecticides. The damage to cowpea pods was also significantly reduced in the sprayed treatments. The first and second sowing dates of cowpea sprayed treatments gave 30% and 45% increase in the seed yield over the first and second unsprayed dates of sowing cowpea treatments, respectively. The first sowing date treatment gave significantly higher seed yield than the second sowing date treatments. There were significant differences in the number of some major insect pests and also on pod damage among the ten diverse cowpea genotypes grown under the Delmarva field conditions. This study provides information on the incidence of insect pests of cowpea in the Delmarva region, the potential of insect pests to cause significant yield losses, and variation in insect pest resistance among ten diverse cowpea genotypes.

Reduction of Salmonella in ground chicken using a bacteriophage

&NA; This studys goal was to ascertain the effectiveness of a commercially available Salmonella bacteriophage during ground chicken production focusing on: water source, different Salmonella serovars, and time. Salmonella‐free boneless, skinless chicken meat was inoculated with 4.0 Log CFU/cm2 of either a cocktail of 3 Salmonella isolates derived from ground chicken (GC) or a cocktail of 3 Salmonella strains not isolated from ground chicken (non‐GC). Bacteriophages were spread onto the chicken using sterile tap or filtered water for 30 min or 8 h. Salmonella was recovered using standard plating method. Greater Salmonella reduction was observed when the bacteriophage was diluted in sterile tap water than in sterile filtered water: 0.39 Log CFU/cm2 and 0.23 Log CFU/cm2 reduction after 30 min, respectively (P < 0.05). The non‐GC isolates showed reductions of 0.71 Log CFU/cm2 and 0.90 Log CFU/cm2 after 30 min and 8 h, respectively (P < 0.05). The GC isolates were less sensitive to the bacteriophage: 0.39 Log CFU/cm2 and 0.67 Log CFU/cm2 reductions after 30 min and 8 h, respectively (P < 0.05). In conclusion, bacteriophage reduction was dependent on water used to dilute the bacteriophage, Salmonellas susceptibility to the bacteriophage, and treatment time.

Effect of Coal Combustion By-products on Phosphorus Runoff from a Coastal Plain Soil

Coal combustion by-products can lower soil phosphorus (P) solubility, but few studies have assessed their effect on runoff P. A soil with elevated P content was amended with fluidized bed combustion ash, flue gas desulfurization gypsum, and anthracite refuse ash at rates of 0–40 g kg−1 soil, and runoff from small plots was monitored over 3 years. In the first year, by-products lowered dissolved P in runoff by up to 47% below the untreated control; however, effects did not persist into the remaining years of the study. Total P losses were not significantly affected by coal combustion by-products, likely because of elevated particulate P losses. Water-extractable P was up to 40% less in treated soils than in untreated soils across the 3 years. Results demonstrate that although coal combustion by-products readily lower P solubility in soils, their impact on P losses in runoff can be undermined by erosional processes.

The Potential of Bt Corn as a Trap Crop for the Control of Corn Earworm, Helicoverpa zea Boddie, in Soybean

ABSTRACT Corn and soybean are two important crops in the Delmarva (Delaware, Maryland and Virginia) peninsula region. Both crops are attacked by corn earworm (CEW), Helicoverpa zea (Boddie). The larvae cause significant ear damage to corn serving as a primary nursery for CEW populations which shift to soybean later in the season. In soybean, CEW larvae cause serious yield losses if not controlled by insecticides. Many farmers in the Delmarva region have been increasing the acreage they grow with genetically engineered corn hybrids that contain insecticidal proteins expressed by the genes of Bacillus thurngiensis sub sp. kurstaki (Bt) as an alternative to the application of chemical insecticides. A study was conducted to investigate the use of Bt corn as a trap crop for the management of CEW in soybean. Bt corn was planted as a trap crop in a ten percent of the area of soybean as a peripheral trap, trap in the middle and trap in the intermittent rows in soybean. CEW moths were attracted and observed on the newly formed silks of the ears of Bt corn in all types of traps including peripheral trap, trap in the middle and trap in the intermittents rows planted in soybean. CEW eggs were also observed on the silk of transgenic corn. The moths, eggs and larvae (CEW) were hardly observed in soybean grown as a main crop. Clearly, we were able to divert the CEW adults on Bt corn from soybean. The number of CEW eggs was significantly higher in the peripheral trap and trap in the intermittent rows compared with trap in the middle of the plots, suggesting that Bt corn planted as a peripheral trap crop could be more practicable and effective for the farmers in reducing the CEW damage in soybean.

Survival and Persistence of Nonpathogenic Escherichia coli and Attenuated Escherichia coli O157:H7 in Soils Amended with Animal Manure in a Greenhouse Environment

Animal manure provides benefits to agriculture but may contain pathogens that contaminate ready-to-eat produce. U.S. Department of Agriculture National Organic Program standards include 90- or 120-day intervals between application of manure and harvest of crop to minimize risks of pathogen contamination of fresh produce. Data on factors affecting survival of Escherichia coli in soils under greenhouse conditions are needed. Three separate studies were conducted to evaluate survival of nonpathogenic E. coli (gEc) and attenuated E. coli O157:H7 (attO157) inoculated at either low (4 log CFU/ml) or high (6 log CFU/ml) populations over 56 days. Studies involved two pot sizes (small, 398 cm(3); large, 89 liters), three soil types (sandy loam, SL; clay loam, CL; silt loam, SIL), and four amendments (poultry litter, PL; dairy manure liquids, DML; horse manure, HM; unamended). Amendments were applied to the surface of the soil in either small or large containers. Study 1, conducted in regularly irrigated small containers, showed that populations of gEc and attO157 (2.84 to 2.88 log CFU/g) in PL-amended soils were significantly (P < 0.05) greater than those in DML-amended (0.29 to 0.32 log CFU/g [dry weight] [gdw]) or unamended (0.25 to 0.28 log CFU/gdw) soils; soil type did not affect E. coli survival. Results from study 2, in large pots with CL and SIL, showed that PL-amended soils supported significantly higher attO157 and gEc populations compared with HM-amended or unamended soils. Study 3 compared results from small and large containers that received high inoculum simultaneously. Overall, in both small and large containers, PLamended soils supported higher gEc and attO157 populations compared with HM-amended and unamended soils. Populations of attO157 were significantly greater in small containers (1.83 log CFU/gdw) than in large containers (0.65 log CFU/gdw) at week 8, perhaps because small containers received more regular irrigation than large pots. Regular irrigation of small pots may have affected E. coli persistence in manure-amended soils. Overall, PL-amended soils in both small and large containers supported E. coli survival at higher populations compared with DML-, HM-, or unamended soils.