Shiga-toxigenic E. coli O157: Reservoirs and Transmission Routes John R. Dunn, DVM, PhD Tennessee Department of Health Centers for Disease Control and Prevention

Shiga-toxigenic E. coli (STEC) Intestinal bacterial flora Gram negative rods Somatic or O antigen (LPS) Flagellar or H antigen Serotype O:H STEC virulence factor complement Hemolysin Intimin Shiga toxin

Shiga toxin Distinguishing virulence factor Subunit toxin: A: acts at ribosomal level, inhibits protein synthesis B: binds glycolipid receptor in mammalian cells (renal endothelium) Stx1, Stx2 Stx2 variants: 2c,2d,2e,2f

Human pathogens Symptoms: Diarrhea Hemorrhagic colitis Hemolytic Uremic Syndrome (HUS) Thrombotic thrombocytopenic purpura (TTP)

E. coli O157:H7

1993 Large western states outbreak, 500 cases and 4 deaths E. coli O157 Emergence CDC-MMWR. 1993. Association of STEC with HUS, Karmali et al. Karmali et al. 1985. J.Infect.Dis. Description of Shiga toxin: O’Brien, others O’Brien and Holmes. 1987. Microbiol.Rev. O’Brien and LaVeck. 1983. Infect.Immun. 1982 First clinical isolation, “Rare E. coli serotype” Riley et al. 1983. NEJM

Ruminant reservoir Gansheroff and O’Brien (PNAS,2000): “…Higher prevalence rates than previously estimated” Selective enrichment & Immunomagnetic separation (IMS)- Sensitive methods Conventional culture techniques: Swab samples Direct plating +/- broth enrichment

Ruminant (Bovine) Reservoir Asymptomatically colonized- transient but common intestinal flora Seasonal- summer peak, winter nadir Endemically unstable- by feedlot, pen, individual, farm, week Periodic high isolation rates (epidemics)- feces, hide, oral cavity, environment, carcass

Two habitat model Primary habitat: Excretion Re-colonization Environment Death Primary habitat: large intestine, recto-anal junction? warm, constant nutrient rich vigorous growth Secondary habitat: water, soil, sediment cool, fluctuating nutrient limiting survival

E. coli O157:H7 Epidemiology 1. Trends- FoodNet data 2. Transmission routes

Foodborne Diseases Active Surveillance Network (FoodNet) Established in 1996 Principle foodborne disease component of Emerging Infections Program (EIP) DHHS (CDC, FDA), USDA (FSIS), and 10 participating state health departments

2004 FoodNet Catchment Area Catchment population 44.1 million persons 15.2% of U.S. population

2004 Preliminary FoodNet Data Pathogen Total # isolates Cases per 100,000 Salmonella 6,464 14.7 Campylobacter 5,665 12.9 Shigella 2,231 5.1 Cryptosporidium 613 1.3 E. coli O157 401 0.9 Yersinia 173 0.39 Vibrio 124 0.28 Listeria 120 0.27 Cyclospora 15 0.03

E. coli O157:H7 HP 2010 1.0 / 100,000

Incidence of E. coli O157 infections, by state, 1999-2002 Isolates / 100,000 pop/ year 3.0 – 6.2 1.7 – 2.9 0.9 – 1.6 0.2 – 0.8

2 E. coli O157 1 Relative Rate 0.8 0.7 0.6 -42 (-54 to -28) 0.5 1996-1998 1999 2000 2001 2002 2003 2004 Year

Consistency in data sources: Decline in E. coli O157 FoodNet surveillance data- declines overall and in high incidence sites FSIS data

Prevalence of E. coli O157:H7 in Ground Beef1 1 Results of raw ground beef products analyzed for E. coli O157:H7 in federal plants. * In 1998 FSIS increased sample size from 25 g to 375g. ** In July 1999 FSIS changed to a more sensitive analytical method.

Foodborne transmission

Has HACCP led to a reduction in human incidence? Excretion Re-colonization Environment Death

Direct and indirect contact transmission

Direct contact transmission

Indirect contact (environmental) transmission

Recent fair outbreaks- E. coli O157 Fair Year # Ill Medina county (OH) 2000 27 Lorain county (OH) 2001 111 Ozaukee county (WI) 2001 59 Wyandot county (OH) 2001 88 Lane county (OR) 2002 60 Calaveras county (CA) 2002 4 Fort Bend county (TX) 2003 25 North Carolina State Fair 2004 108 Florida (multiple fairs) 2005 >30

Summary STEC- diverse serotypes Shiga toxin- distinguishing virulence factor O157:H7 most common, best characterized STEC O157:H7 Ruminant (cattle) reservoir Survival for long periods in the environment

Summary (cont) STEC O157:H7 decline in FoodNet (HP 2010) Consistent with FSIS data Transmission from multiple sources Foodborne Direct and indirect animal contact (fairs and farms)

STEC public health challenges Understand the epidemiology of Non-O157 STEC Food safety Ground beef / tenderized steaks- recent outbreaks of E. coli O157 Other vehicles- produce / waterborne outbreaks Direct and indirect animal contact Prevention- NASPHV compendium Other measures- restrict children, treat animals, decontaminate environment

Questions?