Michael P. Doyle

Health Risks and Consequences of Salmonella and Campylobacter jejuni in Raw Poultry

Salmonella and Campylobacter jejuni are major human pathogens and poultry and poultry products are frequent vehicles of these bacteria. Estimates place the annual incidence of human salmonellosis and campylobacteriosis between 1 and 4 million each. Hazards are associated with contamination, survival or growth during production, transportation, processing and preparation. Animals are contaminated from a variety of sources on farms and the contaminants are spread during processing. Scalding, defeathering, evisceration and giblet operations are major points of spread. Further spread can occur during handling in markets and kitchens. Insufficient thermal processing or cooking allows survival. Improper handling of cooked poultry frequently results in cross contamination from previously handled raw carcasses and parts. Improper refrigeration provides conditions for multiplication of salmonellae. Estimates of annual costs of poultry-associated cases of salmonellosis and campylobacteriosis in the United States range from

Summer meeting 2007 – the problems with fresh produce: an overview

64 million to

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

114.5 million and

Escherichia coli O157: H7 and its significance in foods

362 million to

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

699 million, respectively. The need for a cost-effective solution to these poultry-borne human disease problems is apparent.

Survival of enterohemorrhagic Escherichia coli O157:H7 in water.

In Fall 2006, four separate outbreaks of foodborne illness associated with the consumption of fresh produce occurred in the United States. In follow‐up investigations, spinach, lettuce, and tomatoes were identified as the vehicles of illness. Epidemiologic investigations subsequently focused on finding the specific growing regions using traceback records. While the areas most likely involved in the outbreaks have been identified, the specific mode of contamination remains unconfirmed. Suspected risk factors in these cases include: proximity of irrigation wells and surface waterways exposed to faeces from cattle and wildlife; exposure in fields to wild animals and their waste materials; and improperly composted animal manure used as fertilizer. Difficulty in deciphering these and other on‐farm routes of contamination is due to the sporadic nature of these events. Hence, evidence to support these contamination modes is based largely on experimental studies in the laboratory and field. Still at issue is the relevance of internalization of pathogens, whether this occurs through the roots and plant vascular tissues of vegetables and fruits or through plant surfaces into cracks and crevices. Potential for these events, conditions under which the events occur, and pathogen survival following these events, are questions that still need to be answered. Answers to these questions will ultimately affect the type of interventions needed for application postharvest. Currently, many chemical and biological interventions can reduce surface pathogens and minimize cross‐contamination, however, they are largely ineffective on internalized pathogens. In the event internalization is a significant route of contamination in the field, physical interventions (irradiation and high pressure) may be needed to minimize risk. Ultimately, risk assessment studies will be useful tools in developing risk management strategies for the produce industry.

Lessons from a large outbreak of Escherichia coli O157:H7 infections: insights into the infectious dose and method of widespread contamination of hamburger patties.

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

Escherichia coli O157:H7 was conclusively identified as a pathogen in 1982 following its association with two food-related outbreaks of an unusual gastrointestinal illness. The organism is now recognized as an important cause of foodborne disease, with outbreaks reported in the U.S.A., Canada, and the United Kingdom. Illness is generally quite severe, and can include three different syndromes, i.e., hemorrhagic colitis, hemolytic uremic syndrome, and thrombotic thrombocytopenic purpura. Most outbreaks have been associated with eating undercooked ground beef or, less frequently, drinking raw milk. Surveys of retail raw meats and poultry revealed E. coli O157:H7 in 1.5 to 3.5% of ground beef, pork, poultry, and lamb. Dairy cattle, especially young animals, have been identified as a reservoir. The organism is typical of most E. coli, but does possess distinguishing characteristics. For example, E. coli O157:H7 does not ferment sorbitol within 24 h, does not possess beta-glucuronidase activity, and does not grow well or at all at 44-45.5 degrees C. The organism has no unusual heat resistance; heating ground beef sufficiently to kill typical strains of salmonellae will also kill E. coli O157:H7. The mechanism of pathogenicity has not been fully elucidated, but clinical isolates produce one or more verotoxins which are believed to be important virulence factors. Little is known about the significance of pre-formed verotoxins in foods. The use of proper hygienic practices in handling foods of animal origin and proper heating of such foods before consumption are important control measures for the prevention of E. coli O157:H7 infections.

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

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.

Escherichia coli O157:H7 epidemiology, pathogenesis, and methods for detection in food

Several recent Escherichia coli O157:H7 outbreaks associated with both drinking and recreational water raise concerns about waterborne illness caused by this pathogen. The survival characteristics of a mixture of five nalidixic acid-resistant E. coli O157:H7 strains (10(3) CFU/ml) in filtered and autoclaved municipal water, in reservoir water, and in water from two recreational lakes were determined for a period of 91 days at 8, 15 or 25 degrees C. Greatest survival was in filtered autoclaved municipal water and least in lake water. Regardless of the water source, survival was greatest at 8 degrees C and least at 25 degrees C. E. coli O157:H7 populations decreased by 1 to 2 log10 by 91 days at 8 degrees C, whereas the pathogen was not detectable (> or 3 = log10 decrease) within 49 to 84 days at 25 degrees C in three of the four water sources. SDS-PAGE of surface antigens of surviving cells revealed that there was no major alteration in lipopolysaccharide pattern, but outer membrane protein composition did change. These studies indicate that E. coli O157:H7 is a hardy pathogen that can survive for long periods of time in water, especially at cold temperatures. However, direct viable counts of E. coli O157:H7 determined by acridine orange staining remained essentially the same for 12 weeks at 25 degrees C, whereas viable counts on tryptic soy agar plates decreased to undetectable levels within 12 weeks. Results suggest that E. coli O157:H7 can enter a viable but nonculturable (VBNC) state in water.