Introduction%20to%20Food%20Microbiology%20and%20Surveillance%20for%20Foodborne%20Illness

1
Introduction to Food Microbiology and
Surveillance for Foodborne Illness

• Kali Kniel, Ph.D.
• Associate Professor, Microbial Food Safety
• Department of Animal and Food Sciences

2
Foodborne illness (FBI)

• Infection or intoxication caused by transfer of
  microbial or chemical contaminants from food or
  drinking water to a human
• Over 250 different foodborne diseases and are
  constantly changing due to emerging microorganisms

3
Food Related Illness and Death in the US

• Centers for Disease Control and Prevention (CDC),
  Dr. Elaine Scallan and others, 2011
• 47.8 million cases, of which, an estimated
• 9.4 million illnesses caused by 31 known
  pathogens
• 38.4 million illnesses caused by unspecified
  agents
• 128,000 hospitalizations
• 3000 deaths
• Are numbers meaningful?
• Baseline data
• Underreporting/mild disease

4
Salmonella - National incidence of the top three
serotypes 1970-2001
Typhimurium
Enteritidis
Heidelberg
5
Outbreaks vs Cases

• Case an instance of a particular disease
• Outbreak an incident in which 2 or more cases of
  a similar illness result from eating the same
  food (2 or more unrelated cases)
• Exception 1 case of a chemical-related fbi or
  Clostridium botulinum poisoning constitutes an
  outbreak

6

• Surveillance drives the cycle of public health
  prevention

Surveillance
Epidemiologic investigation
Prevention Measures
Applied Targeted Research
7
Changes in outbreak scenarios

• Classic church supper or Sunday picnic are now
  multi-state outbreaks
• Need information to design useful fbi control
  programs

8
Microbiology Basics

• Whats the difference between a bacteria, a
  virus, a protozoa, a helminthe, a chemical?
• Which ones may grow in your food? Does that
  matter?
• Whats an infection and what is an intoxication?

9
Bacteriology Basics

• Characterization by spore formation
• Characterization by shape
• Characterization by Gram stain (1884)
• Gram positive (purple)
• Gram negative (pink)

Outer membrane
Peptidoglycan
Peptidoglycan
Plasma membrane
Plasma membrane
Periplasmic space
10
(No Transcript)
11
Bacterial Growth
12
Viral Growth
13
Parasite Growth
14
Microbiology Basics

• Factors affecting growth and/or illness
• Nutrients
• pH
• Water availability (Aw)
• Temperature
• Atmosphere
• Manipulate these in terms of Food Preservation
  Food Safety
• How?

15
Process Foods to Enhance Quality Safety

• What factors can enhance a shelf life and the
  safety of the product?
• Pasteurized milk
• Bagged salads
• Packaged deli meats
• Ready to eat sliced apples
• Technologies
• Heat (pasteurization)
• Enhanced packaging films, active packaging
• High pressure processing

16
Foods Most Often Involved

• Beef-ground beef
• Produce
• Seafood-fish, shellfish
• Other meats
• Dairy products
• Ready-to-eat (RTE)/Ready-to-heat
  (RTH)/Ready-to-cook (RTC)
• Why?

17
Most Common Agents

• Campylobacter
• Salmonella
• Staphylococus aureus
• Escherichia coli O157H7
• Clostridium perfringens
• Listeria monocytogenes
• Viruses (Norovirus, Hepatitis A)
• Protozoa (Cryptosporidium, Cyclospora, Toxoplasma)

18
Clinical Features

• Transmission
• Pathogenesis
• Host factors
• Organism factors
• Carriers
• Recognizing FBI
• Control and prevention

19
Symptoms

• Acute symptoms most common
• Often self-limiting
• Chronic sequelae more common
• Diarrhea (5 types), cramps, nausea, fever,
  vomiting, body aches
• gt3 or 4 loose stools within a 24 hour period
• Warning sign is bloody diarrhea

20
Factors contributing to outbreaks

• Improper holding temperature
• Danger zone 40-140F
• Inadequate cooking
• Improper cooling
• Improper reheating
• Poor personal hygiene
• Cross-contamination
• Poor storage practices

21
Biofilm development
biology.binghamton.edu/davies/research.htm
22
Factors Affecting Disease

• Microorganism factors
• Gene expression
• Potential for damage or stress to microorganism
• Interaction of microorganism with food
• pH susceptibility
• Interaction with other microorganism

23
Factors Affecting Disease

• Host factors
• Immunocompromised
• Age
• Pregnancy
• Medications, chemotherapy, diabetes
• Gastric acid

24
(No Transcript)
25
Changing Epidemiology-Agent

• Newly recognized pathogens
• non-O157 shiga-toxin producing E. coli
• Cyclospora cayetanensis
• New variant CJD
• New resistance
• Salmonella Typhimurium DT 104
• Salmonella Newport
• Ciprofloxacin resistant Campylobacter

26
Foodborne Outbreak Scenarios

• Traditional scenario
• usually event associated, or affects a discrete
  population
• acute and localized
• high inoculum, high attack rate
• Newer scenario
• diffuse and widespread
• low-level contamination of widely distributed
  food product

27

• A large outbreak in one place may be obvious

28

• An outbreak with cases dispersed in many places
  may be difficult to detect, unless

• We test the pathogens from all the cases, and
• We find they are infected with precisely the same
  bacterial strain

29
FB Disease Surveillance

• Disease Prevention and Control
• Knowledge of Disease Causation
• Administrative Guidance

30
Burden of Illness
http//www.cdc.gov/foodnet/surveillance_pages/burd
en_pyramid.htm
31
Foodborne Outbreak Surveillance

• Local Health Departments
• Patient complaints
• Laboratory, HCW CMR reports
• State Health Departments
• Foodborne outbreak reports
• Salmonella serotyping
• PFGE
• Federal Health Agencies (CDC and regulatory)
• PulseNet and FoodNet

32
Surveillance

• Passive surveillance occurs when health agencies
  are contacted by cases, physicians or
  laboratories, which report illnesses or
  laboratory results to them.
• In active surveillance, the health agencies
  regularly contact physicians and laboratories to
  make sure that reportable diseases have been
  reported and required clinical specimens or
  isolates have been forwarded to state
  laboratories for further analysis.

33
Disease Reporting

• Passive surveillance system
• Mandatory disease reporting to LHD
• LHD case follow-up and further investigation if
  needed
• LHD transmit data to DHS to CDC
• For select agents, must report immediately

34
Notifiable foodborne diseases

• Food Net - Foodborne Diseases Active Surveillance
  Network (CDC, USDA, FDA)
• Salmonella, Shigella, Campylobacter, Escherichia
  coli O157, Listeria monocytogenes, Yersinia
  enterocolitica, Vibrio and Cryptosporidium and
  Cyclospora

35
Objectives of FoodNet

1. Determine the burden of foodborne illness in the
   United States
2. Monitor trends in the burden of specific
   foodborne illness over time
3. Attribute the burden of foodborne illness to
   specific foods and settings
4. Develop and assess interventions to reduce the
   burden of foodborne illness

36
PulseNet

• A national network of public health
• and food regulatory agency laboratories
  coordinated CDC.
• The network consists of state health
  departments, local health departments, and
  federal agencies (USDA/FSIS, FDA).
• PulseNet participants perform standardized
  molecular subtyping (or fingerprinting) of
  foodborne disease-causing bacteria by
  pulsed-field gel electrophoresis (PFGE).
• PFGE can be used to distinguish strains of
  organisms at the DNA level. DNA fingerprints,
  or patterns, are submitted electronically to a
  dynamic database at the CDC. These databases are
  available on-demand to participantsthis allows
  for rapid comparison of the patterns

37
Objectives of PulseNet

1. Detect foodborne disease case clusters by PFGE
2. Allow for real-time communication among state,
   local health departments, and international
   partners
3. Facilitate early identification of common source
   outbreaks
4. Help food regulatory agencies identify areas
   where implementation of new measures are likely
   to increase the safety of our food supply

38
DNA Fingerprinting by PFGE ?

• Isolates are obtained from patients, food, etc
• DNA is isolated
• DNA is cut into fragments with an enzyme
• DNA fragments loaded into a gel matrix and are
  separated using an electric field

39
What is PFGE?
Large Fragments
Small Fragments
40
3
1
4
2
41
(No Transcript)
42
(No Transcript)
43
Surveillance Data Limitations

• Many but not all foodborne pathogens are
  reportable diseases to the local health dept from
  physicians laboratories
• Underreporting issues
• Estimated that for every 1 case of Salmonella
  that is diagnosed, 38 cases are undiagnosed
• Not all reported cases are foodborne
• Person to person, animal contact, water

44
The outbreak

• So what happens when surveillance indicates that
  an fbi outbreak is occurring?

45
Initial Call

• Calls from physicians reporting patients with
  symptoms of fbi
• Call from Community Health Department
• Increase in laboratory reports
  

46
Steps in Outbreak Investigation

• 1. Verify the Diagnosis

47
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

1. Verify the diagnosis
2. Confirm the outbreak

48
What could account for the increase in cases?
49
What could account for the increase in cases?

• Real increase
• Increase in population size
• Changes in population characteristics
• Random variation
• Outbreak

• Artificial increase
• Increased examination of stools
• New testing protocol
• Changes in reporting procedures

50
Initial Investigation

• Any other way to see if there is a relationship
  between these isolates?

51
Molecular Epidemiology

• DNA fingerprinting
• Pulsed Field Gel Electrophoresis (PFGE) most
  common in outbreak investigations
• A cluster of isolates with the same PFGE pattern
  suggests they arose from the same parent (same
  source)
• Still need an epidemiologic investigation

52
PFGE pattern of E. coli Isolates
53
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

1. Verify the diagnosis
2. Confirm the outbreak
3. Case definition

54
Case Definition

• Outbreak investigation definition
• 1. what symptoms
• 2. where
• 3. onset of symptoms (dates)
• 4. stool culture or PFGE pattern
• Advantages? Disadvantages?

E. coli O157H7 isolated from a stool culture or
development of hemolytic-uremic syndrome in a
school-age child resident of the county with
gastrointestinal symptoms beginning between
November 3 and November 8, 2009.
55
Case Definition

• Advantages
• Lab confirmation increases specificity of case
  definition
• Reduces misclassification maximizes power to
  detect source.
• Disadvantages
• Lab confirmation
• Excludes patients who didnt see MD, were not
  examined, or no PFGE.
• Decreases the sensitivity of the case definition
• Possibly leads to a misrepresentation of case
  characteristics.
• Limiting cases to certain area
• excludes visitors who became infected inhibits
  recognition of extension of outbreak into other
  states.
• Dates reasonable?
• Could limit the number of secondary cases
  included in the study

56
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

• Verify the diagnosis
• Confirm the outbreak
• Case definition
• Descriptive Epidemiology

57
Characterization of Cases

• How does this compare this to national data?
• What does it tell you?

58
Epidemic Curve
59
Epidemic Curves

• How to set it up
• What it tells you
• Mode of transmission
• Propagated
• Common source
• Timing of exposure
• Course of exposure

60
Epidemic Curves
Point Source (Also called Common source point
exposure (e.g., Salmonella))
61
Epidemic Curves
Common source person-to person / propagated
exposure
62
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

• Verify the diagnosis
• Confirm the outbreak
• Case definition
• Descriptive Epidemiology
• Develop a hypothesis

63
Developing a Hypothesis
Ask questions!!But of whom.And when...
64
Determining the Probable Period of Exposure

• Mean/Median incubation period
• Minimum/maximum incubation period

65
Estimating date of exposure
Maximum incubation 21 days
Probable time of exposure
Minimum incubation 14 days
66
Focus of Questionnaire

• Demographic information
• Clinical details of the illness with date of
  onset, duration, and severity of symptoms
• visits to health care providers or hospitals, and
  laboratory results
• A complete food history in the last 7 days
• Water exposure in the last 7 days
• Exposure to other ill persons in the last 7
  days
• Exposure to children in day care in the last 7
  days
• Exposure to a farm or farm animals in the last
  7 days
• Travel outside the immediate area in the last 7
  days

67
Hypothesis of Investigators

• Consumption of food x is associated with infection

68
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

• Verify the diagnosis
• Confirm the outbreak
• Case definition
• Descriptive epidemiology
• Develop a hypothesis
• Test the hypothesis

69
Pick a Control Group

• 1-2 controls selected for every case
• Matched to the case by
• Age group
• (0-lt2 years, 2-lt5 years, 5-lt12 years, 12-lt18
  years, 18-lt60 years, and 60 years)
• Gender
• Random digit dialing
• Neighborhood controls
• Other patients of same physician

70
Steps in Outbreak Investigation

• Verify the diagnosis
• Confirm the outbreak
• Case definition
• Descriptive epidemiology
• Develop a hypothesis
• Test the hypothesis
• Refine hypothesis / Execute additional studies

Steps 1 and 2 are interchangeable
71
Refine Hypothesis/Additional Studies

• What control measures might you consider at this
  point?
• What further studies might you do?

72
Additional Studies

• Culture implicated sprouts
• Parts of the traceback study
• distributor, processor, and producer examination
  of the chain of production from the farm to the
  table
• Applied research on microbial contaminant

73
What Interventions are Needed?

• 1) The immediate problem with this implicated
  food/water
• 2) The larger issue of this food/water as
  vehicles for pathogenic

74
Steps in Outbreak Investigation
Steps 1 and 2 are interchangeable

• Verify the diagnosis
• Confirm the outbreak
• Case definition
• Descriptive epidemiology
• Develop a hypothesis
• Test the hypothesis
• Refine hypothesis / Execute additional studies
• Implement control and prevention measures
• Communicate findings

75
Communicate Findings

• Halt distribution and remove from the marketplace
  
• Hold meetings for public health officials to
  explain routes of contamination
• Public television and radio announcements about
  the risk of contaminated foods and recommending
  persons at high risk for complications not eat
  the food/water
• Government regulatory agencies should begin
  working with the implicated industry to identify
  ways to make food safer for human consumption.

76
Conclusion

• Many steps involved in the process to investigate
  foodborne illness outbreaks.
• Begins with an understanding of the chemical,
  physical, and microbial hazards.
• There are many players involved in this process
• From ensuring food safety
• To investigating
• And implementing control measures
• Makes a great learning system for discussing
  principles of food safety, microbiology,
  epidemiology, and so much more!