Transcript Slide 1

The Role of the Laboratory in
Foodborne Outbreak Investigations
Dubai, February 17, 2014
Cheryl Bopp, M.S.
Unit Lead, Epidemic Investigations Laboratory
Enteric Diseases Laboratory Branch
404-639-1798
[email protected]
Epidemic Investigations Laboratory
CDC
♦ A unit of the Enteric
Diseases Laboratory Branch
♦ Responsibility: To conduct
laboratory investigations of
outbreaks of foodborne and
waterborne bacterial
diseases
2
Enteric Diseases Laboratory Branch:
Foodborne Bacteria and Toxins
♦ Salmonella, Shigella, diarrheagenic Escherichia coli,
Yersinia enterocolitica, and Cronobacter sakazakii
in infants
♦ Campylobacter
♦ Listeria
♦ Vibrio cholerae, Vibrio parahaemolyticus, Vibrio spp.
♦ Foodborne toxins
– Clostridium botulinum and Clostridium perfringens
– Bacillus cereus
– Staphylococcus aureus
Outline
♦ Why investigate foodborne disease outbreaks?
♦ Foodborne outbreak investigations in the United
States
– Role of clinical laboratories
– Role of local and state public health laboratories
♦ Example of a foodborne outbreak investigation
Why Investigate Foodborne Disease
Outbreaks?
♦ Identify the etiologic agent and food vehicle(s)
♦ Contain the outbreak by removing the
contaminated food from distribution
♦ Share information with food regulatory agencies
and the food industry so that in the future similar
outbreaks may be prevented
♦ Learn about newly emerging pathogens and
their modes of transmission
Role of Clinical Laboratories
in Foodborne Outbreak Investigations
♦ Responsibility of clinical microbiology
laboratories:
– Test clinical specimens
– Report the isolation of foodborne pathogens to the
physician
♦ In the US, clinical laboratories are crucial in
detecting foodborne outbreaks because they:
– Report suspected outbreaks to public health
authorities
– Forward isolates from suspected foodborne
illness to local or state public health laboratories
Role of Local and State Public Health
Laboratories in Outbreak Investigations
1.
2.
3.
4.
Provide advice on specimen collection
Receive food, environmental specimens for testing
Receive clinical specimens for testing
Receive isolates from clinical laboratories for
identification, serotyping, and DNA fingerprinting
by PFGE
5. Perform PFGE and submit DNA fingerprints to
PulseNet (or send isolates to another public health
lab for PFGE)
6. Interpret and report laboratory results to the
outbreak investigation team
Role of the Public Health Laboratory
in Foodborne Outbreak Investigations
1. Advise the outbreak investigation team
on specimen collection
- What type of specimens to collect
- How many specimens and the volume of
each specimen for optimal culture results
- How to store and transport specimens to the
public health laboratory
What Types of Specimens to Collect
♦ Clinical specimens
–
–
–
–
Fecal
Blood cultures
Serum
Vomitus, etc.
♦ Food specimens
♦ Water and environmental
specimens
♦ Animal Specimens
CDC Guidelines for
Collection of Fecal Specimens
http://www.cdc.gov/foodsafety/outbreaks/investigating-outbreaks/specimen-collection.html
Food, Environmental, and Animal
Specimens
2. Receive food, environmental, animal
specimens
– To conserve laboratory resources,
nonclinical specimens are tested only for
the implicated pathogen
– Decide on optimal detection methods for
the outbreak pathogen
– Culture methods
– Molecular methods (immunoassay, PCR, etc)
♦ Serotype and PFGE all isolates of the
outbreak pathogen
Limitations of Food Testing for
Confirmation of Outbreak Vehicle
♦ In many outbreak investigations, food testing is
negative for the etiologic agent. Reasons include:
– The food item was incorrectly identified as the vehicle
– The food vehicle was not available for collection and other
non-epidemiologically relevant foods were tested instead
– The food was contaminated during preparation and not
before (unprepared food not contaminated)
– Food not evenly contaminated with the pathogen so
sampling and testing of a portion of the vehicle may
produce false negative results
– The laboratory methods were inadequate
Collection of Water Samples in
Foodborne Outbreaks
♦ Collect water if investigation suggests
– cross contamination of foods by water
– outbreak is waterborne not foodborne
♦ Well water and surface waters (streams,
rivers, ponds, lakes) may be
contaminated with Salmonella,
Campylobacter, or E. coli O157:H7 in
rural or agricultural areas
– PFGE of patient and water isolates may be
crucial to implicate the water source
Collection of Environmental Samples
♦ Surfaces
♦ Food preparation equipment
– Slicers, blenders, etc.
♦ Other samples
– Soil
– Sawdust
Collection of Animal Specimens
♦ Animals are often colonized with
Salmonella, Campylobacter, or
E. coli O157:H7 , etc.
– cattle and other ruminants such
as goats, sheep
– poultry
– household pets (dogs, cats,
reptiles, frogs)
Role of the Public Health Laboratory
in Foodborne Outbreak Investigations
3. Receive clinical specimens for culture
♦ If clinical laboratory testing did not determine the
pathogen, the public health laboratory tests for
additional pathogens
– An important role of public health laboratories is to
maintain capacity to test for all important foodborne
pathogens and toxins
• Examples: norovirus, Cl. perfringens, Staph enterotoxin
– Or the public health laboratory may forward specimens to
another laboratory
Top 5 US Foodborne Pathogens
2000-2008; http://www.cdc.gov/foodborneburden
♦ Top 5 US foodborne pathogens (estimated percent
of all foodborne disease)
– Norovirus (58%), Nontyphoidal Salmonella (11%),
Clostridium perfringens (10%), Campylobacter spp. (9%),
Staphylococcus aureus (3%)
♦ In the US, clinical laboratories often test stools only
for Salmonella, Shigella, Campylobacter
♦ Public health laboratory testing essential to detect
outbreaks of norovirus, C. perfringens, Staph
enterotoxin
CDC Guidelines for Confirmation of
Foodborne Disease Outbreaks
♦ http://www.cdc.gov/outbreaknet/references_resources/
guide_confirming_diagnosis.html
♦ Information on incubation period, clinical syndrome,
and confirmatory testing for:
–
–
–
–
Bacterial agents
Chemical agents
Viral agents
Parasitic agents
Guidelines for Confirmation of
Foodborne Disease Outbreaks
http://www.cdc.gov/outbreaknet/references_resources/guide_confirming_diagnosis.html
Etiologic
agent
Incubation
period
Clinical
syndrome
Confirmation of Etiology
Table B-1. Guidelines for confirmation of foodborne-disease outbreaks (Bacterial)
Etiologic agent
Incubation period
Clinical syndrome
Campylobacter
jejuni/coli
2-10 days;
usually 2-5 days
Diarrhea (often
bloody), abdominal
pain, fever
Clostridium
perfringens
6-24 hrs
Nontyphoidal
Salmonella
Staphylococcus
aureus
Confirmation
Isolation of organism from clinical specimens from two or more ill persons
OR
Isolation of organism from epidemiologically implicated food
Diarrhea, abdominal Isolation of 106 organisms/g from stool of two or more ill persons,
cramps; vomiting and provided specimen is properly handled. OR
fever uncommon
Demonstration of enterotoxin in the stool of two or more ill persons OR
Isolation of 105 organisms/g from epidemiologically implicated food,
provided specimen is properly handled
6 hrs-10 days; Diarrhea, often with fever Isolation of organism of same serotype from clinical specimens from two or
usually 6-48 hrs and abdominal cramps more ill persons OR
Isolation of organism from epidemiologically implicated food
30 min-8 hrs;
usually 2-4 hrs
Vomiting, diarrhea
Isolation of organism of same phage type from stool or vomitus of two or more
ill persons OR
Detection of enterotoxin in epidemiologically implicated food OR
Isolation of 105 organisms/g from epidemiologically implicated food, provided
specimen is properly handled
Isolation of Pathogens from Diarrheal
Outbreaks of Unknown Etiology
CDC Algorithm
fecal specimen
XLD or HEK
Shigella
Salmonella
MAC
TCBS
Vibrio cholerae
Shigella
Salmonella Vibrio parahaemolyticus
E. coli
TET or SEL
Broth
HEK
CVA
Sub 37oC TET to new TET,
Incubate at 42oC
CIN or SS
25oC
2 days
Campylobacter E. coli O157:H7 Yersinia
enterocolitica
Jejuni/coli
Salmonella
diarrheagenic E. coli: STEC, ETEC,
EPEC, EIEC
CTSMAC
HEK
Role of the Public Health Laboratory
in Foodborne Outbreak Investigations
4. Receive isolates from clinical laboratories
– Confirmation of identification of pathogen
– Serotyping of pathogen
• Salmonella and E. coli serotyping important
– Toxin testing (C. perfringens, E. coli)
– DNA fingerprinting by PFGE
Role of the Public Health Laboratory
in Foodborne Outbreak Investigations
5. Perform PFGE and submit DNA fingerprints
to the PulseNet Database
– If laboratory does not have PFGE capacity,
isolates are sent to another public health lab for
PFGE testing
Why does CDC use PFGE instead of
other DNA fingerprinting methods?
♦ PFGE is the most epidemiologically relevant
method for E. coli O157:H7 and Salmonella
– A 1993 investigation of an E. coli O157:H7 outbreak in
the western United States first demonstrated the utility
of PFGE as a DNA fingerprinting method
♦ Because of PulseNet highly standardized methods
and Bionumerics software, PFGE fingerprints from
different laboratories can be compared
Evolution of Subtyping
for Bacteria
PFGE MLST
REA
MLVA
isAFLP MBMS*
MEE
The future of subtyping
Phage
Ribotyping
wholetyping
genome sequencing
Serotyping
Plasmid profiles
RAPD
Bacteriocin typing
1920
1940
1960
1980
* Microarray-based multi-target sequencing
2000
Role of the Public Health Laboratory
in Foodborne Outbreak Investigations
♦ Report and interpret laboratory results for
the outbreak investigation team
– Provide written reports of laboratory results to
the investigation team leader and interpret the
significance of the results
– Provide timely updates of ongoing testing
• Speed versus accuracy: If presumptive results are
reported, the laboratory must clearly state that the
results have not been confirmed
An example of an outbreak
investigation
♦ Cereal-associated outbreak of Salmonella
serotype Agona infections in multiple
states, 1998
– Role of the clinical laboratories
– Role of the public health laboratories
Clinical laboratories isolated Salmonella
enterica serotype Agona from 23 cases in
Illinois and 9 cases in Pennsylvania
♦ Clinical laboratories
isolated Salmonella
♦ Forwarded isolates to
state public health
laboratories for
serotyping
Public health laboratories in Illinois, Pennsylvania,
and other states reported a large increase in
Salmonella serotype Agona isolates
Preliminary results by state outbreak
investigation teams implicated one brand of
toasted oats cereal from one grocery store chain
♦ Interviewed 11 patients: all mentioned grocery
store chain A as their regular grocery store
♦ 10/11 mentioned purchasing plain toasted oats
cereal from the store
♦ No other common food item or social event
identified
♦ Contacted grocery store chain A and producer of
plain toasted oats cereal
♦ All states with cases had grocery store chain A
Public health laboratory testing: all Salmonella
Agona isolates from cases who ate the implicated
cereal had the same PFGE DNA “fingerprint”
♦ In addition, Salmonella Agona isolates from
persons who had not consumed the implicated
brand of cereal had different PFGE “fingerprints”
State outbreak investigation teams conducted
a case-control study: ill persons were 20 times
more likely to have eaten the implicated cereal
♦ 74 ill persons in 10 states enrolled; 151 healthy
household members used as controls
♦ Phone interview
– Shopping habits
– Cereal consumption
– Other food items associated with salmonellosis
♦ Ill persons 20 times more likely to have eaten
plain toasted oats cereal produced by Company
B
♦ No other food item implicated
State public health laboratories and the CDC
isolated Salmonella Agona from the implicated
cereal
♦ Toasted oats obtained from case homes (open
packages) tested at state public health
laboratory and CDC by multiple methods
♦ S. Agona isolated from toasted oats cereal by
state public health laboratories and CDC
♦ Unopened packages from the same lot obtained
from Company B sent to federal regulatory
agency laboratory for testing
♦ Regulatory agency isolates S. Agona from
cereal in intact packages
Public health laboratories performed PFGE on
Salmonella Agona isolates from cereal and
DNA fingerprints match human isolates
C
C
Outcomes of the Outbreak
Investigation
♦ The cereal product
was recalled by the
manufacturer.
♦ CDC recommended
that consumers not
eat the cereal
product.
♦ Additional infections
were prevented.
Lessons from this outbreak
investigation
♦ Laboratories were critical to outbreak recognition
– Clinical laboratories isolated Salmonella and forwarded
isolates to public health laboratories
– Public health laboratories serotyped and PFGE
fingerprinted clinical isolates
– Public health laboratories isolated the outbreak strain of
Salmonella serotype Agona from the implicated food
♦ Timely communication between laboratorians,
epidemiologists and regulatory officials enabled
rapid identification of the food vehicle
Thank you!