Microbiological Foodborne Threats

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Microbiological Foodborne Threats

• Michael P. Doyle

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Microbiological Foodborne Threats

• Immediate Threats
• Produce
• Imported Foods

3
Microbiological Foodborne Threats

• Near- to Long-Term Threats
• Antimicrobial Resistance
• Influences of Global Warming
• At-Risk Subpopulations
• Alternative Processing Technologies/ Convenience
  Foods

4
Produce A Pathogen Vehicle of Increasing Public
Health Significance
5
Foodborne Disease Outbreaks and Outbreaks-
Associated Cases in U.S., 1990-2003

• More than 3,500 reported foodborne disease
  outbreaks in the United States between 1990 and
  2003
• ? Number of outbreaks for which category of food
  could be identified as the vehicle
• Commodity No. of outbreaks No. of cases
  associated
• 
  
  with outbreaks
• Seafood 723 8,071
• Multi-ingredient foods 601 18,006
• Produce 432 25,823
• Poultry 354 11,894
• Beef 343 10,872
• Eggs 309 10,750
• ? Produce was vehicle of outbreaks having the
  highest average number of reported
• cases
• Center for Science in the Public Interest,
  CSPIs Oubreak Alert

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Increased Consumption of Fresh Fruits and
Vegetables
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Examples of Recent Produce-Associated Outbreaks
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Salmonella Newport Outbreak in UK

• More than 360 cases of S. Newport infection in
  England, Scotland, Northern Ireland and Isle of
  Man between Sept 9 and Oct 7, 2004
• Vehicle Iceberg lettuce (OR 11.43,
  P 0.009) purchased at fast food/take away
  restaurants

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Multistate Hepatitis A Outbreak Associated with
Green Onions

• Three outbreaks of hepatitis A infection during
  Sept. Oct. 2003
• ? OCharleys, Knoxville, TN (70 cases)
• ? One metro Atlanta and two central Georgia
  restaurants (ca. 230 cases)
• ? Chi-Chis, Monaca, PA (gt 550 cases)
• CDC, Morbid. Mortal. Weekly Report. 521155-1157
  (2003)
• J.A. Gabel et al. Abstr. Intl. Conf. Emerging
  Infect. Dis. p. 187,
• No. 108 (2004)

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Multistate Hepatitis A Outbreak Associated with
Green Onions

• Green onions imported from Baja California,
  Mexico, were vehicle
• ? At one restaurant, onions were prepared by
  rinsing intact bundles, cutting off the roots,
  and removing the rubber bands
• ? Onions were chopped and held refrigerated for
  up to 3 days and periodically added to 40 to
  80-qt. batches of salsa
• CDC, Morbid. Mortal. Weekly Report. 521155-1157
  (2003)
• J.A. Gabel et al. Abstr. Intl. Conf. Emerging
  Infect. Dis. p. 187,
• No. 108 (2004)

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Hepatitis A Outbreak Associated with Raw
Blueberries

• Sharp increase in cases of hepatitis A in first
  four months of 2002 in Auckland, New Zealand (81
  lab-confirmed cases between 1/1-5/31/02)
• ? High percentage of cases were from higher
  socio-economic areas, of European ethnicity and
  had not traveled outside New Zealand
• ? This suggested vehicle was a seasonal food
  that was more expensive and not widely
  consumed
• Case-control study revealed vehicle was
  blueberries (OR7.6), with a population
  attributable risk of 51
• L. Calder et al. Epidemiol. Infect. 131745-751
  (2003)

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Hepatitis A Outbreak Associated with Raw
Blueberries

• ? Site investigation of implicated blueberry
  orchard revealed a 9-year-old child who was
  present in the orchard during the harvest (late
  Dec. early Jan.) developed symptoms compatible
  with hepatitis A and was IgM-positive on Jan.
  29, 2002
• ? Food safety audit revealed multiple
  opportunities for an infected worker to
  contaminate product fecally during picking and
  packing
• Orchard had 3 pit latrines, of which one was in
  the middle of blueberry plants and two were 30 m
  from the plants

13
Cyclosporasis Outbreak Associated with Snow Peas

• In May - July 2004, 96 cases of Cyclospora
  cayetanensis infection associated with a
  residential facility in Pennsylvania
• Associated with pasta salad containing raw snow
  peas imported from Guatemala
• Snow peas were the vehicle of Cyclospora

CDC Morbid. Mortal. Weekly Report 53(37)876
(2004)
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Outbreaks of Yersinia pseudotuberculosis
Infection from Grated Carrots

• 103 cases (based on case definition) of Y.
  pseudotuberculosis O1 infection identified among
  school children in Kotka City in Finland in May
  2003
• Case-control study identified grated carrots as
  vehicle (OR4.7 multivariable analysis)
• ? Carrots were traced back to a domestic farm
  where Y. pseudotuberculosis O1 (same genotype
  as patients) was isolated from 5
• of 13 samples taken from a peeling machine
• K. Jalava et al. Abstr. Int. Conf. Emerging
  Infect. Dis. 2004,
• p. 194

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What are common features of many recent
produce-associated outbreaks?

• Produce was grown outside US
• Raises questions regarding safety of imported
  produce
• Failings in good agricultural practices (GAPs)

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Effect of chlorinated water on Salmonella on
shredded lettuce and diced tomatoes
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Need effective antimicrobial treatments for
produce that have been validated for killing
enteric pathogens and retaining fresh-like
characteristics of treated products
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Imported Foods A Growing Public Health Threat
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Imported Foods

• Sanitation practices for food production and
  preparation are not universally equivalent
  throughout the world
• Importing foods can move pathogens from areas
  where pathogen is indigenous to locations where
  it seldom or does not exist
• Example, Cyclospora in raspberries from Guatemala
  to US and Canada

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U.S. Imports of Fresh Fruit and Vegetables
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Pathogen Contamination of Produce

• Sources of pathogens
• Irrigation water
• Processing water
• Poor personal hygiene of infected foodhandlers
• Sewage/manure used as foil fertilizer
• Address these contributors to pathogen
  contamination by using Good Agricultural
  Practices (GAPs)
• Major deficiencies in GAPs for vegetable and
  fruit production and processing in many countries
  exporting to the US

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Prevalence of Salmonella and Shigella on Imported
Produce

• FDA assayed 1003 imported produce samples from
  March 99 - October 00 for Salmonella, Shigella
  and E. coli O157H7
• 35 positive for Salmonella
• 9 positive for Shigella
• 0 positive for E. coli O157H7
• FDA 2001 (http//www.cfsan.fda.gov/dms/prodsur6.h
  tml)

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Prevalence of Salmonella and Shigella on
Imported Produce
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Prevalence of Salmonella and Shigella on Domestic
(US) Produce

• FDA assayed 1028 US-grown produce samples from
  May 00 - Jan 02 for Salmonella, Shigella and E.
  coli O157H7
• 6 positive for Salmonella
• 5 positive for Shigella
• 6 positive for E. coli O157H7
• FDA 2003 (http//www.cfsan.fda.gov/dms/prodsu10.h
  tml)

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Prevalence of Salmonella and Shigella on
Domestic (US) Produce
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U.S. Imports of Meat, Poultry and Seafood
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Fecal Waste Used in Aquaculture Production

• Raw domestic sewage and effluent from sewage
  treatment plants is frequently used in fish
  farming in many Asian countries
• Estimates at least two-thirds of the world
  production of farmed fish is grown in ponds
  fertilized with animal manure or human sewage

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Microbiological Food SafetyIssues Associated
with Seafood

• Fishery products can be contaminated with human
  pathogens
• FDA survey (2001) detected Salmonella in 7 of
  farm-raised shrimp and in lt1 of wild-harvested
  shrimp
• Most shrimp consumed in U.S. is imported, with a
  high percentage aquacultured in tropical
  countries
• Salmonella is in natural flora of pond-cultured
  shrimp in tropical countries chicken manure is
  often used to fertilize aquaculture ponds

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Import Inspection of US Food Supply

• In FY 1997, FDA electronically screened 2.7
  million entries of imported foods under its
  jurisdiction, but physically inspected only 1.7
  (46,000 entries)
• In CY 1997, FSIS visually inspected all 118,000
  entries of imported meat and poultry under its
  jurisdiction, and conducted 20 physical
  examination on ca. 20 of entries

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Imported Food Inspections

• Dr. Lester Crawford, Acting Commissioner of FDA,
  testimony to House Appropriations Committee's
  subcommittee on agriculture on March 11, 2004
• FDA is overwhelmed by imports which have
  increased 5-fold since 1994
• Due to FDA's lack of resources, a mere 1 of
  imported food is inspected

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Near- to Long-Term Microbiological Foodborne
Threats
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Antimicrobial Resistance

• Antibiotics
• Issue with foods consumed uncooked or made from
  raw ingredients and not further processed
• Further processing (pasteurization) kills
  antibiotic-resistant foodborne pathogens
• Disinfectants/Sanitizers
• Potential concern if consistent use of some
  sanitizing regimes in food processing facilities
• Need to rotate treatments in processing
  facilities to prevent development of resistance

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Influences of Global Warming

• Increased temperature of seawater
• Increase in pathogenic vibrios (V. cholerae, V.
  parahaemolyticus, V. vulnificus) in shellfish
• Shift in species composition of algae to more
  toxic dinoflagellates

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At Risk Subpopulations

• Host's underlying health status, age, and
  practices related to health and diet have a
  bearing on susceptibility to foodborne pathogens
• Increase in immunosuppressed subpopulations
  because of medical advances in treatment of
  diseases or body function deficiencies
• Greater sensitivity to opportunistic or
  nontraditional pathogens
• Examples, Listeria monocytogenes, Enterobacter
  sakazakii, Enterococcus faecalis and E. faecium

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"At Risk" Populations for Listeriosis

• Continuum of risk of acquiring listeriosis based
  on host susceptibility

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Relative susceptibilities for non-pregnant
sub-populations, based on the incidences of
listeriosis cases (outbreak and sporadic) in
these groups in 1992 (WHO/FAO, 2004)
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Relative susceptibility for different
sub-populations based on the incidences of
listeriosis cases (outbreak and sporadic) in
these groups (WHO/FAO, 2004)
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Define "At Risk" Populations

• Exquisitely sensitive
• Very high risk of listeriosis
• Transplant patients and individuals on cancer
  therapy
• At increased risk
• Higher risk of listeriosis than normal healthy
  population but less sensitive than exquisitely
  sensitive
• Includes elderly, pregnant women and most
  immunocompromised

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Define "At Risk" Populations

• Very low risk
• Normal healthy population
• Unique "high risk" subpopulations
• Pregnant Latina women (likely associated with
  consumption of contaminated queso fresco/ blanco
  cheese)

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Must all ready-to-eat foods such as fresh fruits
and vegetables be free of opportunistic pathogens
to make food safe for all at risk populations?
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Food Processing or Formulation Changes and
Convenience Foods

• Attempts to reduce costs, provide convenience
  foods, or improve nutritional value of foods
  through processing modifications, product
  formulation, or new product development can
  create conditions for a microbiological
  catastrophe

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Fresh-cut Produce Processing

• Have moved early stages of processing iceberg
  lettuce to the field increased risk of microbial
  contamination
• Lettuce heads are cut at stem and exterior leaves
  and core are removed
• Core area and exterior of head are treated with 5
  to 200 ppm chlorinated water
• Lettuce is loaded by conveyor belt into plastic
  bag-lined bins and cooled down within 2 hr
• Rain (mud) and wind increase contamination
  potential
• Some processors are packaging fresh-cut lettuce
  in field

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Reduced-Salt Foods

• Sodium chloride (salt) is an important
  preservative in many foods (e.g., process cheese,
  cured meat)
• Can prevent botulism
• Reducing sodium chloride content can provide
  conditions for toxin production by C. botulinum

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Fresh-cut Melons are a Convenience Food Pushing
the Limits of Safety
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Fresh-cut Melons are Pushing the Limits of Safety

• pH of melons
• Cantaloupe 6.2 - 7.1
• Honeydew 6.3 - 6.7
• Watermelon 5.2 - 5.8
• Examples of Outbreaks
• gt400 cases of salmonellosis - cantaloupe at salad
  bars
• 18 cases of salmonellosis - watermelon cut at
  supermarket
• 17 cases of salmonellosis - watermelon cut at
  supermarket
• 206 cases of norovirus infection - melon cut by
  infected foodhandler

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Fresh-cut Melons are Pushing the Limits of Safety

• Pathogen growth on precut melons
• 106 increase of Salmonella in watermelon at 23oC
  for 24 h
• 105 increase of Listeria monocytogenes in
  watermelon at 20oC for 2 d
• 104 increase of Listeria monocytogenes in
  Valenciano amarelo (Brazilian) melon at 10oC for
  4 d or 20oC for 1 d
• Salmonella generation times at 23oC
• Cantaloupe - 1.2 h
• Honeydew - 1.1 h
• Watermelon - 1.0 h

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Concluding Comments

• Increased consumption of fresh produce,
  especially fresh-cut, coupled with increased
  importation of produce which generally has higher
  levels of pathogen contamination, is a leading
  threat to the safety of foods

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Concluding Comments

• Consumer demands for convenient, fresh-like,
  healthful foods on a year-round basis creates
  great marketing opportunities for food processors
  but increasing challenges for food microbiologists