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)
• 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.
Reported Outbreaks and Cases—US (1998) Subtyping Issues • 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)
Some Methods Used for Typing E. coli O157:H7 Strains
Toxin gene screening Thomas et al., 1996; Ostroff et al., 1989 Plasmid profiling Ostroff et al., 1989; Paros et al., 1993;
Meng et al., 1995; Radu et al., 2001 Phage typing Ahmed et al., 1987; Khakhria et al.,
1990; Barrett et al., 1994 Antibiotic susceptibility testing Kim et al., 1994; Farina et al., 1996;
Radu et al., 2001; Restriction fragment length polymorphism with phage λ (λ -RFLP)
Paros et al., 1993;Samadpour et al., 1993
Ribotyping Martin et al., 1996; Roberts et al., 2001
Pulsed-field gel electrophoresis (PFGE) Bohm and Karch, 1992;Barrett et al., 1994;Meng et al., 1995;Radu et al., 2001
PCR using randomly amplified polymorphic DNA (RAPD) sequences Swaminathan and Barrett,1995; Radu et
al., 2001 PCR using highly repetitive sequences (rep-PCR) None specific for E. coli-O157:H7;
Johnson and O’Bryan, 2000 Amplified fragment length polymorphism analysis (AFLP)
Iyoda et al., 1999; Zhao et al., 2000
How Does PulseNet Work? 1. PFGE 2. Pattern electronic database at local,
state or federal level 3. Uploaded to national database at CDC 4. CDC searches for clusters of patterns 5. Local cluster searches 6. Clusters posted to Listserve.
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Changes in Outbreaks
• Food consumption and practices in US have changed during the past 20 years
• Shift from the typical point source, or “church supper” outbreak, which is relatively easy to detect to the more diffuse, widespread outbreaks that occur over many communities with only a few illnesses in each community.
Changes in Outbreaks Continued • 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 outbreak detection algorithm (SODA), impact ability to identify and investigate these new types of outbreaks
How does subtyping help in epidemiologic investigations?
• Identifies cases within an outbreak • Distinguishes outbreak cases from concurrent
