1. Good Agricultural Practices
Microorganisms of Concern in Production Agriculture

2. Practical Food Microbiology
Microorganisms are small, living unicellular or multicellular.
They include bacteria, viruses, yeasts, molds, and parasites.
They can be….
The good
The bad, and
The ugly!

3. Kinds of Microorganisms
The Good (or helpful):
Add them to foods or they are there naturally.
They ferment foods to preserve them and/or create unique flavors and textures.
Examples: cheese, yogurt, sour cream, bread, sauerkraut and pickles.

4. Kinds of Microorganisms
The Bad (or spoilage)
Change foods and cause them to “go bad” or spoil.
Examples: Discolored, mushy, or fuzzy vegetables; sour milk; and slimy, putrid meat.

5. Kinds of Microorganisms
The Ugly (disease-causing, pathogenic):
Illness can range from mild to life-threatening.
Examples include foods contaminated with Salmonella or E. coli O157:H7. Common signs and symptoms include nausea, vomiting, and diarrhea.

6. Microorganisms that cause...
Food spoilage -
Affect aroma, texture and/or appearance of food
Foodborne illness -
May or may not affect sensory characteristics of the food.
Only laboratory testing can tell if harmful microorganisms or toxins are present – some are difficult to detect or cannot be detected.

7. Current Problems With Harmful Microbes
Some people are more vulnerable to foodborne illness:
Young children or elderly people.
Immuno-compromised individuals.
New ways of transmitting organisms:
Widespread food distribution system.
New food formulations and handling practices.
Changes in food choices.
New or evolving pathogens:
Example - E. coli 0157:H7.

8. Examples of Harmful Microorganisms of Concern in Fresh Produce
Bacteria
Viruses
Salmonella species
E. coli O157:H7
Shigella species
Bacillus cereus
Listeria monocytogenes
Vibrio cholera
Hepatitis A virus
Norwalk-like virus
Parasites
Cyclospora
Cryptosporidium
Giardia

9. Harmful Microorganisms & Outbreaks Associated with Produce

10. Where Microbial Pathogens Live
Residents of human and animal intestinal tracts…
Salmonella species
E. coli O157:H7
Shigella species
Campylobacter jejuni
Viruses and parasites
Common in soils…
Listeria monocytogenes
Bacillus cereus
Clostridium botulinum
Clostridium perfringens

11. Microbes That Cause Foodborne Illness
Bacteria – Single-celled organisms that live independently.
Viruses - small particles that live and replicate in a host.
Parasites - intestinal worms or protozoa that live in a host animal or human.
Bacteria
Viruses
Parasites

12. Bacteria... Cause the greatest number of foodborne illnesses.
Single-celled organisms that live independently.
Invisible to the naked eye: Must be magnified 1,000 times to be seen.
400 million bacteria are equal to a grain of sugar in size.

13. To Grow & Cause Illness, Bacteria Need:
Moisture, found in most foods, including fruits and vegetables.
Nutrients, provided by most foods.
Warmth, especially room temperature or a little higher.
Time

14. Bacteria Increase in Number by Dividing in Two
With ideal conditions, they double every half hour.
1 becomes 2, 2 become 4, 4 become 8, and so on...
In 12 hours, 1 cell could multiply into 33 million cells!
Usually you start with many bacterial cells, not just one.

15. The Bacterial Growth Cycle has Four Phases12
stationary
death 8
log cfu/ml
exponential 4
lag
time

16. Bacteria Are Found Everywhere
In air, soil, and water
In intestines of animals & humans
On skins of fruits & vegetables
On raw meat, poultry, & seafood
On shells of nuts
On insects & rodents
On hand, skin, hair, & clothing of people

17. 3 Harmful Foodborne Bacteria
E. coli 0157:H7
Salmonella
Listeria

18. E. coli / E. coli O157:H7
E. coli: common microbe in animal and human intestinal tracts.
Most strains of E.coli are not harmful.
But harmful strains, such as E. coli 0157:H7, cause severe illness.

19. E. coli O157:H7 First recognized as human pathogen in 1982.
Outbreaks often associated with undercooked ground beef.
Produce associated outbreaks have involved lettuce, unpasteurized apple cider & juice, radish sprouts, and alfalfa sprouts.

20. E. coli O157:H7 Naturally exists in animals without symptoms
cattle, sheep, deer, dogs, cats, other animals
Can contaminate/grow on fresh produce:
minimally processed cantaloupe
watermelon cubes
shredded lettuce
sliced cucumbers
mesclun lettuce
Cattle and other ruminants are considered major reservoirs, prevalence in sheep is also high, other animals healthy animals also carry i157, shed the organism in into environment, contaminate the ground water on farm
human can be healthy carriers
not surprisingly contamination of meat during slaughter is principle route by which O157 enter the food supply
ground beef has high contamination rate many outbreak of O157 associated with consumption of undercooked ground beef, other foods implicated include roast beef, venison jerky, salami, raw milk, pasteurized milk, yogurt, lettuce, unpasteurized apple cider/juice, cantaloupe, radish sprouts and alfalfa sprouts,
note-worthy, certain foods such as apple cider and dry-cured salami, considered previously as safe because of high acidity, not heated before consumption, have been vehicles of outbreaks
recreational lake water, reports of person-to-person and waterborne transmission

21. Contamination of Fruits and Vegetables by E. coli O157:H7
Wild or domestic animals.
Improperly composted animal manure.
Fruits and vegetables dropped on the ground have a higher chance of being contaminated by manure.
Water may carry and spread organisms.
Farm and packing house workers, as well as any food handlers, may also contaminate produce.
Cattle and other ruminants are considered major reservoirs, prevalence in sheep is also high, other animals healthy animals also carry i157, shed the organism in into environment, contaminate the ground water on farm
human can be healthy carriers
not surprisingly contamination of meat during slaughter is principle route by which O157 enter the food supply
ground beef has high contamination rate many outbreak of O157 associated with consumption of undercooked ground beef, other foods implicated include roast beef, venison jerky, salami, raw milk, pasteurized milk, yogurt, lettuce, unpasteurized apple cider/juice, cantaloupe, radish sprouts and alfalfa sprouts,
note-worthy, certain foods such as apple cider and dry-cured salami, considered previously as safe because of high acidity, not heated before consumption, have been vehicles of outbreaks
recreational lake water, reports of person-to-person and waterborne transmission

22. Foodborne Illness Caused by E. coli O157:H7
Causes severe cramps, bloody diarrhea, vomiting, dehydration.
Severe complications can include kidney failure, strokes, seizures, and sometimes painful death.
Onset days; lasts days, unless there are complications.
Cattle and other ruminants are considered major reservoirs, prevalence in sheep is also high, other animals healthy animals also carry i157, shed the organism in into environment, contaminate the ground water on farm
human can be healthy carriers
not surprisingly contamination of meat during slaughter is principle route by which O157 enter the food supply
ground beef has high contamination rate many outbreak of O157 associated with consumption of undercooked ground beef, other foods implicated include roast beef, venison jerky, salami, raw milk, pasteurized milk, yogurt, lettuce, unpasteurized apple cider/juice, cantaloupe, radish sprouts and alfalfa sprouts,
note-worthy, certain foods such as apple cider and dry-cured salami, considered previously as safe because of high acidity, not heated before consumption, have been vehicles of outbreaks
recreational lake water, reports of person-to-person and waterborne transmission

23. Salmonella species More than 2300 types.
About 200 types cause human illness.
Comes from intestinal tracts of poultry, pigs, birds, and insects.
Also can be carried by humans.
Infective dose – a few cells to millions.
DT104 widely distributed in a variety of different food animals including cattle, sheep, pigs, goats, chickens, turkeys, as well as domestic pets, e.g., house cats
causes sever diarrhea in cattle, higher mortality rate contact with sick animals is a significant risk factor
Mode of contamination: infected animals, human feces

24. Salmonella species
Isolated from many types of raw fruits and vegetables – not a frequent event.
Outbreaks linked to:
tomatoes
bean sprouts
melons
unpasteurized orange juice and apple juice
DT104 widely distributed in a variety of different food animals including cattle, sheep, pigs, goats, chickens, turkeys, as well as domestic pets, e.g., house cats
causes sever diarrhea in cattle, higher mortality rate contact with sick animals is a significant risk factor
Mode of contamination: infected animals, human feces

25. Foodborne Illnesses Caused by Salmonella species
Illness causes nausea, vomiting, abdominal cramps, diarrhea, fever, and headache.
Symptoms occur in hours and last days in otherwise healthy people.
May last weeks in immuno-compromised people.
Secondary problems such as reactive arthritis or pericarditis may result in some patients.
DT104 widely distributed in a variety of different food animals including cattle, sheep, pigs, goats, chickens, turkeys, as well as domestic pets, e.g., house cats
causes sever diarrhea in cattle, higher mortality rate contact with sick animals is a significant risk factor
Mode of contamination: infected animals, human feces

26. Listeria monocytogenes
Widely distributed in nature.
In soil, sewage, fresh water sediments.
In silage, decaying plant matter.
In animal intestinal tracts.
Animal carriers may not be sick.
Found in raw foods.
Meats, unpasteurized milk.
Vegetables.
Recent studies on the prevalence of Listeria indicated that 2-6% of individuals were positive a more frequent fecal carrier state (10-50%) has been documented in animals, including cattle, poultry, and swine
Listeria had been isolated from a variety of food products, including fresh vegetables (11%), raw meats 13%, raw milk 3-4%, dairy products 3%, as well as eggs and seafood products

27. Foodborne Illness Caused by Listeria monocytogenes
Causes flu-like symptoms in healthy people.
May progress to meningitis, blood poisoning, abortion in pregnant women, or death.
Symptoms appear within 1 day to 3 weeks.
Duration depends on treatment.
High fatality rate in immune-compromised individuals.

28. Other Microbial Hazards: Viruses
Excreted in feces by infected individuals.
Can be carried by raw produce, uncooked food.
Persists for weeks or months on crops or in soils.
Examples
Hepatitis A on lettuce, raspberries, and strawberries.

29. Virus Transmission
Viruses can be transmitted to plants and fresh fruits and vegetables by:
People.
Tractors, equipment, clippers.
Insects.
Viruses can also cause plant and animal diseases.
By preventing virus transmission, plant diseases can be decreased and produce safety can be increased.

30. How Viruses Reproduce
All viruses use a host cell’s biosynthetic machinery to multiply.
Essentially, the virus invades a cell, uses the cell’s equipment to replicate its own nucleic acid and protein coat, and then releases the new viruses from the cell.
In bacteria, this process can be achieved in minutes and in animals, it usually requires hours.

31. One Virus of Concern: Hepatitis A
An infected person can spread the disease to others well before the symptoms of Hepatitis A are present.
It is primarily transmitted by person-to-person contact through fecal contamination, but can also be spread through food and water.
Causes fever, nausea, vomiting, abdominal cramps, extreme fatigue, jaundice (affects the liver).
Onset days after ingestion.
Lasts 1-2 weeks to months in severe cases.

32. Controlling the Spread of Hepatitis A and other Viruses on the Farm
Proper sanitation on the farm including care of equipment and in-field sanitation.
Training farm workers and encouraging them to practice proper hygiene can greatly reduce the risk of contaminating fresh fruits and vegetables with Hepatitis A.

33. Handwashing Information
Study of handwashing
<2 times/day in restaurants, foodservice, healthcare settings
94 % say they wash their hands
68% of those observed wash their hands
FDA estimates
poor handwashing contributes to 80 million cases of illnesses in U.S

34. Remember: proper handwashing and appropriate field sanitation facilities reduce risk.

35. Other Microbial Hazards: Parasites
Single-celled microorganisms.
Exist as cysts outside animals; require animal or human intestinal tract to multiply and spread.
Spread by fecal contamination of water or fresh produce.
Examples of outbreaks:
Giardia: raw vegetables, fruits.
Cryptosporidium: unpasteurized apple juice.
Cyclospora: imported raspberries, basil, mesclun lettuce.

36. Parasites: Cryptosporidium
Cysts in water or food infect intestinal cells.
Infection causes illness and allows the parasite to reproduce.
Causes watery diarrhea, stomach cramps, nausea, and fever.
Symptoms days after ingestion; can last 4 days to weeks.

37. Parasites: Cyclospora
Cyclospora parasites infect the small intestine.
Causes watery diarrhea (sometimes explosive), loss of appetite, bloating, stomach cramps, nausea,vomiting, muscle aches, low-grade fever, weight loss, and fatigue.
Some cases are without symptoms.
Symptoms 1 week after consuming contaminated food or water, can last more than a month and can return later.
Cyclospora

38. Parasites: Giardia
Common parasite that infects animal and human intestines.
Causes diarrhea, abdominal cramps, nausea, and vomiting.
Symptoms 1 -2 weeks after ingestion of cysts in contaminated food or water.
Lasts weeks in healthy people, but can last years in some cases.
Giardia

39. PREVENTION is the Key to Reducing Microbial Contamination of Fresh Fruits and Vegetables
Learn more about PREVENTION in other Good Agricultural Practices presentations.

40. The End

41. Acknowledgements Original presentation created by Donna L. Scott,
Yuan Chen, Elizabeth A. Bihn, and Robert B. Gravani.
Presentation edited and updated by Merle Pierson.
Images and graphs provided by Yuan Chen,
Donna L. Scott, Elizabeth A. Bihn and original images of Cryptosporidium, Cyclospora, and Giardia from DPDx (Identification and Diagnosis of Parasites of Public Health Concern, Centers for Disease Control and Prevention).