Xiuping Jiang

Persistence of enterohemorrhagic Escherichia coli O157:H7 in soil and on leaf lettuce and parsley grown in fields treated with contaminated manure composts or irrigation water

Outbreaks of enterohemorrhagic Escherichia coli O157:H7 infections associated with lettuce and other leaf crops have occurred with increasing frequency in recent years. Contaminated manure and polluted irrigation water are probable vehicles for the pathogen in many outbreaks. In this study, the occurrence and persistence of E. coli O157:H7 in soil fertilized with contaminated poultry or bovine manure composts or treated with contaminated irrigation water and on lettuce and parsley grown on these soils under natural environmental conditions was determined. Twenty-five plots, each 1.8 by 4.6 m, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but treated with contaminated water) and five replication plots for each treatment. Three different types of compost, PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline-stabilized dairy manure compost), and irrigation water were inoculated with an avirulent strain of E. coli O157:H7. Pathogen concentrations were 10(7) CFU/g of compost and 10(5) CFU/ml of water. Contaminated compost was applied to soil in the field as a strip at 4.5 metric tons per hectare on the day before lettuce and parsley seedlings were transplanted in late October 2002. Contaminated irrigation water was applied only once on the plants as a treatment in five plots for each crop at the rate of 2 liters per plot 3 weeks after the seedlings were transplanted. E. coli O157:H7 persisted for 154 to 217 days in soils amended with contaminated composts and was detected on lettuce and parsley for up to 77 and 177 days, respectively, after seedlings were planted. Very little difference was observed in E. coli O157:H7 persistence based on compost type alone. E. coli O157:H7 persisted longer (by > 60 days) in soil covered with parsley plants than in soil from lettuce plots, which were bare after lettuce was harvested. In all cases, E. coli O157:H7 in soil, regardless of source or crop type, persisted for > 5 months after application of contaminated compost or irrigation water.

Fate of Escherichia coli O157:H7 in Manure-Amended Soil

ABSTRACT Escherichia coli O157:H7 cells survived for up to 77, >226, and 231 days in manure-amended autoclaved soil held at 5, 15, and 21°C, respectively. Pathogen populations declined more rapidly in manure-amended unautoclaved soil under the same conditions, likely due to antagonistic interactions with indigenous soil microorganisms. E. coli O157:H7 cells were inactivated more rapidly in both autoclaved and unautoclaved soils amended with manure at a ratio of 1 part manure to 10 parts soil at 15 and 21°C than in soil samples containing dilute amounts of manure. The manure-to-soil ratio, soil temperature, and indigenous microorganisms of the soil appear to be contributory factors to the pathogens survival in manure-amended soil.

Fate of Salmonella enterica Serovar Typhimurium on Carrots and Radishes Grown in Fields Treated with Contaminated Manure Composts or Irrigation Water

ABSTRACT Three different types of compost, PM-5 (poultry manure compost), 338 (dairy cattle manure compost), and NVIRO-4 (alkaline-pH-stabilized dairy cattle manure compost), and irrigation water were inoculated with an avirulent strain of Salmonella enterica serovar Typhimurium at 107 CFU g−1 and 105 CFU ml−1, respectively, to determine the persistence of salmonellae in soils containing these composts, in irrigation water, and also on carrots and radishes grown in these contaminated soils. A split-plot block design plan was used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but with contaminated water applied) and five replicates for a total of 25 plots for each crop, with each plot measuring 1.8 × 4.6 m. Salmonellae persisted for an extended period of time, with the bacteria surviving in soil samples for 203 to 231 days, and were detected after seeds were sown for 84 and 203 days on radishes and carrots, respectively. Salmonella survival was greatest in soil amended with poultry compost and least in soil containing alkaline-pH-stabilized dairy cattle manure compost. Survival profiles of Salmonella on vegetables and soil samples contaminated by irrigation water were similar to those observed when contamination occurred through compost. Hence, both contaminated manure compost and irrigation water can play an important role in contaminating soil and root vegetables with salmonellae for several months.

Persistence of Salmonella enterica Serovar Typhimurium on Lettuce and Parsley and in Soils on Which They Were Grown in Fields Treated with Contaminated Manure Composts or Irrigation Water

There are many sources of pathogen contamination of vegetable crops in the field that include manure used as fertilizer and irrigation water. An avirulent strain of Salmonella enterica serovar Typhimurium was added to three different types of composts-PM-5 (poultry manure compost), 338 (dairy manure compost), and NVIRO-4 (alkaline stabilized dairy manure compost)-and irrigation water at 10(7) colony forming units (cfu)/g and 10(5) cfu/mL, respectively, to determine under field conditions the persistence of salmonellae in soils treated with these composts or irrigation water, and also on leaf lettuce and parsley grown on such treated soil. Contaminated compost was applied to soil in the field as a strip at a rate of 4.5 metric tons/hectare on the day before lettuce and parsley seedlings were transplanted. Contaminated irrigation water was applied only once on the plants at the rate of 2 liters per plot on the same day after the seedlings were transplanted. Twenty-five plots, each measuring 1.8 x 4.6 meters, were used for each crop, with five treatments (one without compost, three with each of the three composts, and one without compost but applied with contaminated water) and five replication plots for each treatment. Salmonella persisted for 161 and up to 231 days in soils amended with contaminated composts on which lettuce and parsley, respectively, were grown, and was detected for up to 63 days and 231 days on lettuce and parsley, respectively. The type of contaminated compost had minimal effect on the persistence of S. Typhimurium in soil. Occurrence of Salmonella on vegetables and survival in soil on which these vegetables were grown, irrespective of source of contamination through irrigation water or compost, were similar, suggesting both contaminated manure compost and irrigation water can play important roles in contaminating soil and vegetables with Salmonella for an extended period of time.

Fate of Escherichia coli O157:H7 during Composting of Bovine Manure in a Laboratory-Scale Bioreactor

Inactivation profiles of Escherichia coli O157:H7 in inoculated bovine manure-based compost ingredients were determined by composting these ingredients in a bioreactor under controlled conditions. A 15-liter bioreactor was constructed to determine the fate of E. coli O157:H7 and changes in pH, moisture content, temperature, and aerobic mesophilic and thermophilic bacterial counts during composting. Fresh cow manure, wheat straw, cottonseed meal, and ammonium sulfate were combined to obtain a moisture content of ca. 60% and a carbon/nitrogen ratio of 29:1. The compost ingredients were held in the bioreactor at a constant external temperature of 21 or 50 degrees C. Self-heating of the ingredients due to microbial activity occurred during composting, with stratified temperatures occurring within the bioreactor. At an external temperature of 21 degrees C, self-heating occurred for 0 to 3 days, depending on the location within the bioreactor. E. coli O157:H7 populations increased by 1 to 2 log10 CFU/g during the initial 24 h of composting and decreased by ca. 3.5 log10 CFU/g near the bottom of the bioreactor and by ca. 2 log10 CFU/g near the middle and at the top during 36 days of composting. At an external temperature of 50 degrees C. E. coli O157:H7 was inactivated rapidly (by ca. 4.9 log10 CFU/g at the top of the bioreactor, by 4.0 log10 CFU/g near the middle, and by 5.9 log10 CFU/g near the bottom) within 24 h of composting. When inoculated at an initial level of ca. 10(7) CFU/g. E. coli O157:H7 survived for 7 days but not for 14 days at all three sampling locations, as indicated by either direct plating or enrichment culture. At the top of the bioreactor a relatively constant moisture content of 60% was maintained, whereas the moisture content near the bottom decreased steadily to 37 to 45% over 14 days of composting. The pH of the composting mixture decreased to ca. 6 within 1 to 3 days and subsequently increased to 8 to 9. Results obtained in this study indicate that large populations (10(4) to 10(7) CFU/g) of E coli O157:H7 survived for 36 days during composting in a bioreactor at an external temperature of 21 degrees C but were inactivated to undetectable levels after 7 to 14 days when the external temperature of the bioreactor was 50 degrees C. Hence, manure contaminated with large populations (e.g., 10(7) CFU/g) of E. coli O157:H7 should be composted for more than 1 week, and preferably for 2 weeks, when held at a minimum temperature of 50 degrees C.

Fate of Escherichia coli O157:H7 in Manure Compost-Amended Soil and on Carrots and Onions Grown in an Environmentally Controlled Growth Chamber

Studies were done to determine the fate of Escherichia coli O157:H7 in manure compost-amended soil and on carrots and green onions grown in an environmentally controlled growth chamber. Commercial dairy cattle manure compost was inoculated with a five-strain mixture of green fluorescent protein-labeled E. coli O157:H7 at 10(7) CFU g(-1) and mixed with unsterilized Tifton sandy loam soil at a ratio of 1:5. Baby carrot or green onion seedlings were planted into the manure compost-amended soil in pots, and soil samples surrounding the plant, edible carrot roots and onion bulb samples, and soil immediately beneath the roots were assayed for E. coli O157:H7 in triplicate at weekly intervals for the first 4 weeks, and every 2 weeks for the remainder of the plant growth cycle (up to 3 months). E. coli O157:H7 cell numbers decreased within 64 days by 3 log CFU/g in soil and soil beneath the roots of green onions and by more than 2 log CFU/g on onions. E. coli O157:H7 survived better during the production of carrots, with a 2.3-log CFU/g reduction in soil and a 1.7-log CFU/g reduction on carrots within 84 days. These results indicate that the type of plant grown is an important factor influencing the survival of E. coli O157:H7 both on the vegetable and in the soil in which the vegetable is grown.

Antibacterial Effects of Grape Extracts on Helicobacter pylori

ABSTRACT Anti-Helicobacter pylori activities were determined by agar dilution, confocal laser scanning microscopy, and cell proliferation assays following treatment with various grape extracts. Muscadine grape skin possessed the strongest activity, followed by grape synergy (skin and seed) and seed, suggesting that higher phenolic levels do not necessarily determine overall anti-H. pylori efficacy.

Fate of Escherichia coli O157:H7 during On-Farm Dairy Manure–Based Composting

Studies were conducted to determine the fate of Escherichia coli O157:H7 in dairy manure-based compost in a field setting. Two trials were performed involving duplicate compost heaps constructed at an outdoor fenced site. The compost heaps were composed of dairy manure, old hay, feed waste, a mixture of sawdust and calf feces, and fresh hay. Samples of the composting mixture were inoculated with stx-negative E. coli O157:H7 B6914 at initial concentrations of 10(7) and 10(5) CFU/g for trial 1 and trial 2, respectively. Individual sample bags were placed on the surface and at three locations (top, center, and bottom) within each heap. Although the compost heaps achieved temperatures of 50 degrees C or above at all internal locations for at least 7 days, temperature stratification was observed. In trial 1, E. coli O157:H7 was detected by enrichment through 14 days within the heaps. When inoculated with 10(5) CFU/g in trial 2, E. coli O157:H7 was detected only through days 2, 2, and 5 at the top, center, and bottom locations, respectively. For both trials, the pathogen survived at the heaps surface for up to 4 months. The indicator commensal E. coli and coliforms were inactivated at a rate similar to that for E. coli O157:H7. Results indicate that composting, with periodic heap turning, can be a practical approach to inactivating E. coli O157:H7 in cattle wastes on the farm. Our data also suggest when compost heaps are not turned, E. coli O157:H7 may survive for months at the heap surface.

Fate of Escherichia coli O157:H7 and Salmonella Enteritidis on currency

The fate of foodborne pathogens Escherichia coli O157:H7 and Salmonella Enteritidis on coin surfaces was determined at room temperature (25 degrees C). A five-strain mixture of E. coli O157:H7 or Salmonella Enteritidis of approximately 5 x 10(4) CFU was applied to the surfaces of sterile U.S. coins (pennies, nickels, dimes, and quarters) and to the surfaces of two control substrata (Teflon and glass coverslips). During storage at room temperature, E. coli O157:H7 survived for 7, 9, and 11 days on the surfaces of pennies, nickels, and dimes and quarters, respectively. However, the pathogen died off within 4 to 7 days on both the Teflon and glass surfaces. Salmonella Enteritidis survived for 1, 2, 4, and 9 days on the surfaces of pennies, nickels, quarters, and dimes, respectively. Unlike E. coli O157:H7, survival of Salmonella Enteritidis was greatest on both Teflon and glass coverslips, with more than 100 cells per substratum detected at the 17th day of storage. Results indicate that coins could serve as potential vehicles for transmitting both E. coli O157:H7 and Salmonella Enteritidis.

Thermal Inactivation of Escherichia coli O157:H7 in Cow Manure Compost

Rates of inactivation of a five-strain mixture of green fluorescent protein-labeled Escherichia coli O157:H7 in autoclaved and unautoclaved commercial cow manure compost with a moisture content of ca. 38% were determined at temperatures of 50, 55, 60, 65, and 70 degrees C. Trypticase soy agar with ampicillin was determined to be the best medium for the enumeration of heat-injured and uninjured cells of green fluorescent protein-labeled E. coli O157:H7. The results obtained in this study revealed that in autoclaved compost, E. coli O157:H7 reductions of ca. 4 log CFU/g occurred within 8 h, 3 h, 15 min, 2 min, and < 1 min at 50, 55, 60, 65, and 70 degrees C, respectively. At 65 and 70 degrees C, considerably less time was required to kill the pathogen in unautoclaved compost than in autoclaved compost. Decimal reduction times (D-values) for autoclaved compost at 50, 55, 60, 65, and 70 degrees C were 137, 50.3, 4.1, 1.8, and 0.93 min, respectively, and D-values for unautoclaved compost at 50, 55, and 60 degrees C were 135, 35.4, and 3.9 min, respectively. Considerable tailing was observed for inactivation curves, especially at 60, 65, and 70 degrees C. These results are useful for identifying composting conditions that will reduce the risk of the transmission of E. coli O157:H7 to foods produced in the presence of animal fecal waste.