1 Agents of Foodborne Zoonoses • Illness caused by – Campylobacter spp. – Escherichia coli O157:H7 – Salmonella • 80-95% cases from these bacteria estimated to be foodborne; probably of animal origin • FoodNet data (repeat???) – PulseNet: Molecular epidemiology • Outbreaks and investigations • Carriage by food animals and food • Risk Foodborne Diseases Active Surveillance Network (FoodNet) • Principal foodborne disease component of CDC's Emerging Infections Program • Active surveillance for foodborne diseases and related epidemiologic studies (PulseNet) to better understand the epidemiology of foodborne diseases in the United States. • “Active” surveillance system, meaning public health officials frequently contact laboratory directors to find new cases of foodborne diseases and report these cases electronically to CDC. FoodNet Disease Monitoring • Bacteria – Campylobacter – Escherichia coli O157 – Listeria monocytogenes – Salmonella – Shigella – Vibrio – Yersinia enterocolitica • Parasites – Cryptosporidium – Cyclospora • Viruses – Hepatitis A – Noroviruses FoodNet • 1995, FoodNet surveillance began in five locations: California, Connecticut, Georgia, Minnesota and Oregon • New York and Maryland in 1998, Tennessee in 2000, Colorado in 2001 and New Mexico in 2004). – The total population of the 2004 bacterial catchment is 44.5 million persons, or 15.1% of the United States population. Mead et al (1999) Reported and Estimated Illnesses: Foodborne pathogens--US Mead et al (1999)
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• Principal foodborne disease component ofCDC's Emerging Infections Program
• Active surveillance for foodborne diseases andrelated epidemiologic studies (PulseNet) tobetter understand the epidemiology of foodbornediseases in the United States.
• “Active” surveillance system, meaning publichealth officials frequently contact laboratorydirectors to find new cases of foodbornediseases and report these cases electronically toCDC.
Subtyping• ID cases likely to be part of an outbreak• Eliminate sporadic cases (background noise)• Difficult to select appropriate method
– Tenover et al. (1997)• Salmonella
– Bender et al (2001)– McQuiston et al (2004)
• E. coli O157:H7– Samadpour (1995)
• Campylobacter– Manning et al (2003)
Methods used for typingE. coli O157:H7 strains
• Toxin gene screening
• Plasmid profiling
• Phage typing
• Antibiotic susceptibility testing
• Restriction fragment lengthpolymorphism with bacteriophageλ (λ -RFLP)
• Ribotyping;• Pulsed-field gel electrophoresis• PCR using randomly amplified
polymorphic DNA (RAPD)sequences
• PCR using highly repetitivesequences (rep-PCR)
• Amplified fragment lengthpolymorphism analysis
• Thomas et al., 1996; Ostroff et al.,1989
• Ostroff et al., 1989; Paros et al., 1993;Meng et al., 1995; Radu et al., 2001
• Ahmed et al., 1987; Khakhria et al.,1990; Barrett et al., 1994
• Kim et al., 1994; Farina et al., 1996;Radu et al., 2001;
• Paros et al., 1993;Samadpour et al.,1993
• Martin et al., 1996; Roberts et al., 2001• Bohm and Karch, 1992;Barrett et al.,
1994;Meng et al., 1995;Radu et al.,2001
• Swaminathan and Barrett,1995; Raduet al., 2001
• None specific for E. coli-O157:H7;Johnson and O’Bryan, 2000
• Iyoda et al., 1999; Zhao et al., 2000
How Does PulseNet Work?1. PFGE2. Pattern electronic database at local,
state or federal level3. Uploaded to national database at CDC4. CDC searches for clusters of patterns5. Local cluster searches6. Clusters posted to Listserve.
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Changes in Outbreaks
• Food consumption and practices in UShave changed during the past 20 years
• Shift from the typical point source, or“church supper” outbreak, which isrelatively easy to detect to the morediffuse, widespread outbreaks that occurover many communities with only a fewillnesses in each community.
Changes in OutbreaksContinued• Large food producing facilities that disseminate
products throughout the country• Some few outbreaks that some low level
contamination of food products• Products are distributed among many states• Only a few illnesses occur in each community,• New laboratory and statistical tools, such as
PulseNet and the surveillance outbreakdetection algorithm (SODA), impact ability toidentify and investigate these new types ofoutbreaks
How does subtyping help inepidemiologic investigations?• Identifies cases within an outbreak• Distinguishes outbreak cases from concurrent