Role of PulseNet in Listeriosis Surveillance and Outbreak - - PowerPoint PPT Presentation

Role of PulseNet in Listeriosis Surveillance and Outbreak Investigations

Lewis M. Graves and Bala Swaminathan Foodborne and Diarrheal Diseases Branch National Center for Infectious Diseases Centers for Disease Control and Prevention

Outline

Laboratory-based Surveillance for Listeriosis What is PulseNet—The Role of PulseNet Listeria monocytogenes (Lm) on PulseNet (Goals) Examples of PulseNet at work in Epidemiologic

Investigations

Multistate Outbreak of Listeriosis—United States, 1998

Tracking of Epidemic Clones

PulseNet at Work – Deli turkey meat outbreak, 2000 Listeriosis Outbreak, Northeastern United States – 2002 PulseNet: Future Improvements Conclusions

Lab Based Surveillance for Listeriosis

• Serotyping

Classical typing method based on somatic (O) and flagellar (H) antigens Excellent first level typing method >95% of human Lm infections belong to serotypes 1/2a, 1/2b, and 4b

Ribotyping

Satisfies two requirements for a good subtyping method: typeability and

reproducibility

Discriminating ability, particularly for serotype 4b, may not be adequate for

epidemiological investigations

Automated robotic system commercially available (RiboPrinter, Qualicon) Adequate for screening food processing plant environments

• Pusled-field gel electrophoresis (PFGE)

Molecular subtyping method based on DNA macrorestriction analysis Satisfies the requirements for a good subtyping method: typeability,

reproducibility, and high discriminating ability

Excellent tool for epidemiological investigations

What is PulseNet?

A national network of public health laboratories State health departments, Local health departments,

Federal agencies (CDC, USDA/FSIS, FDA)

Perform standardized molecular typing of

foodborne disease-causing bacteria by Pulsed- field gel electrophoresis (PFGE)

Share DNA “fingerprints” electronically via

Internet

Dynamic database of DNA “fingerprints” at CDC Database available on-demand to participants

Role of PulseNet

Detect foodborne disease case clusters by PFGE Facilitate early identification of common source

• utbreaks

Assist epidemiologists in investigating outbreaks Separate outbreak-associated cases from other sporadic

cases

Assist in rapidly identifying the source of outbreaks Act as a rapid and effective means of communication

between public health laboratories

Listeria monocytogenes

• n PulseNet (Goals)

Early recognition Investigation Identify appropriate controls for case-control

studies

Confirm Food etiology Confirm environmental association Identification of potential virulent and avirulent

strains

Tracking of epidemic clones

Multistate Outbreak of Listeriosis—United States, 1998

• During the 1998 hot dog (Franks) associated outbreak, all L.

monocytogenes PFGE subtyping was done by CDC and only 1 or 2 public health laboratories

101 outbreak-related cases

• Epidemiologic investigation implicated hot dogs
• Outbreak strains (serotype 4b) were isolated from patient’s opened

packages of Franks and unopened packages obtained from Plant B

MPN below the minimum quantifiable limit of 3-tube MPN

• Recall of over 35 million lbs. from Plant B
• Additionally, 3 deli meat products produced at Plant B tested

positive for L. monocytogenes serotype 1/2a

No patient isolate match found Product had been distributed and consumed, but no illness to this product

were identified

Tracking of Epidemic Clones

• Epidemic Clone I (ECI)

Small number of closely related strains of Lm serotype 4b Implicated in numerous outbreaks of foodborne listeriosis during

the past 2 decades in Europe and North America including those in Nova Scotia (coleslaw, 1981), California (Mexican-style cheese, 1985), Switzerland (soft cheese, ), France (pork tongue in aspic, 1992), and others)

• Epidemic Clone II (ECII)

Lm serotype 4b, may represent a novel epidemic-associated

lineage

Identified in the 1998 hot dog outbreak Differed significantly in a portion of the genome that was

• therwise highly conserved among strains of ECI, serotype 4b

Evans et al. (2004) Manuscript in press, AEM

PulseNet at Work 2000

• Sept. 27, 2000: A posting by NY City Public Health

Laboratory on PulseNet Listserv: 8 L. monocytogenes isolates of the same Ribotype and PFGE type in previous 3 months

Search of the National database and replies by

participants identified matching isolates from 7 other states

Epi investigation led to implication of deli turkey meat

product produced by a single food processing facility

Resulted in a recall of 16.8 million pound of product No additional matches seen after recall

ApaI and AscI Digest Pattern of Clinical Isolates Associated With the 2000 Turkey Deli Meat Linked Outbreak

AscI ApaI

Listeriosis Outbreak, Northeastern United States - 2002

• PFGE subtyping by CDC and 6 states helped epidemiologists

separate outbreak related cases from sporadic cases

135 cases between 7/2 – 10/4 46 were the same PFGE pattern

• Epidemiologic investigation implicated turkey deli meat
• USDA/FSIS promptly analyzed food and environmental

samples and subtyped Listeria monocytogenes isolates

• Outbreak strain found in environmental isolates from Plant A

and in intact product from Plant B

• Recall of over 30 million lbs. from Plants A and B
• No additional matches identified after recall of product

AscI ApaI AscI S P F F P F F S P F F P F F S

P= Patient isolate pattern F= Food isolate pattern; S=Standard (H2446)

2002 Outbreak in U.S., Patient-Food Isolate Patterns

Dendrogram showing 186 isolates patterns collected July 1 through Nov. 30, 2002. ApaI pattern for AscI outbreak is shown on the right. Outbreak associated PFGE profile: AscI;ApaI: GX6A16.0235; GX6A12.0003 ApaI AscI

PulseNet: Future Improvements

Achieve real-time subtyping and real-time

communication

Reduce the time it takes for isolates to go from clinical

lab to the state/local public health lab

Reduce the time for PFGE testing of isolates Critical for timely detection of clusters Timely assignment of PulseNet designations for

PFGE patterns

Strengthen collaborations with food industry

Conclusions

PFGE is a valuable part of epidemiologic

and environmental investigations

It allows separation outbreak from sporadic

cases

Identify cases that are likely to be linked Help trace source of contamination