1. Shiga toxin Escherichia coli and Shigella sp.

2. Characteristics of E. coli
Enterobacteriaceae
Gram negative rod, ~ 1 mm in length.
Facultative anaerobe
Non-spore-forming.
All ferment glucose.
Most ferment lactose to gas.
Most are motile.

3. Growth and survival pH range Temperature range Water activity
Indicator organism

4. Other E. coli pathogens (“pathotypes”)
Commensal E. coli
Intestinal:
Enterotoxigenic E. coli (ETEC)
Enteropathogenic E. coli (EPEC)
Enteroaggregative E. coli (EAEC)
Enteroinvasive E. coli (EIEC)
Diffusely adherent E. coli (DAEC)
Enterohemorrhagic E. coli (EHEC)
E. coli O157:H7

5. Images from Dr. Erika A. Taylor’s website
Serotypes
O-antigen
Somatic antigen
>170 known
H-antigen
Flagellar antigen
>60 known
E. coli O157:H7
Images from Dr. Erika A. Taylor’s website

6. Enterohemorrhagic E. coli O157:H7
Birth of a pathogen
Toxin (Shiga toxin)
Disease:
Infectious dose
Incubation period
Symptoms
Progression
Cases per year
Typical food sources
Other sources

7. Lifestyle of EHEC

8. Carcass washer ?

9. Outbreaks Ground beef Unpasteurized apple juice
Spinach and other leafy vegetables
Public drinking water (Walkerton, Ontario)
Sprouts (1996 Osaka, Japan outbreak)
Raw chocolate chip cookie dough (Nestle outbreak)
Raw milk cheese (Costco)
Petting zoos

10. Apple cider
Oct-Dec 1991, 23 patients (mean age 10.8) admitted to Boston area hospitals
Symptoms: diarrhea (96%), abdominal pain (87%), bloody diarrhea (70%), vomiting (35%), fever (17%)
Clinical confirmed E. coli O157:H7

11. The investigation What caused the outbreak? The resolution
What are potential ways E. coli O157:H7 ends up on apples?
The resolution
What new policies came out of this outbreak?
An increased awareness of survival of E. coli O157:H7 in acidic environments.
outbreaks

12. Newly recognized pathogens
Non O157 Shiga toxin E. coli (non-O157 STEC)
Serogroups O26, O45, O111, O103, O121, O145
Typically less virulent
Collectively, about twice as common as O157:H7
Outbreaks (
2014: O121 raw sprouts from Evergreen Fresh Sprouts
: O121 Frozen snack items (Rich Products)
2012: O145 no source identified
2012: O26 raw sprouts at Jimmy John’s

13. “Adulterant”

14. Shigella sp. Four species
S. dysenteriae (group A)
S. flexneri (group B)
S. boydii (group C)
S. sonnei (group D)
About 130,000 cases/year (CDC, 2011); 30% foodborne (5th most common)

15. Similarity to STEC Shigella is a fancy name for E. coli
S. dysenteriae produce Shiga toxin
pH, temperature, aw optimum
Clinical presentation
Low infectious dose
1-7 day incubation period; 3 days typical
Dysentery

16. Differences with STEC Most are non-motile and lactose-negative
Humans are only known reservoir
Year
Outbreak
Species
1987
Rainbow Family gathering; ~6,000 ill
S. sonnei
1990
Operation Desert Shield; 214 soldiers (produce)
Mostly S. sonnei
1991
Moose soup served at community event in Galena, Alaska; 25 ill
1994
SS Viking Serenade cruise ship; ~586 ill (onions)
S. flexneri
2001
Tomatoes distributed to NY restaurants; 800 ill