Foodborne Gastroenteritis Caused by Escherichia coli
645
acid-resistant numbers decreased following a brief period of hay feeding (Figure 27–2). The association
of acid resistance with virulence in some enteropathogens is discussed in Chapter 22.
From a study of E. coli 0157:H7 in fecal samples of commercial feedlot cattle in 2000 from 20
feedlot pens, 636 of 4790 samples (13%) were positive for this organism with the highest prevalence
being in 10 pens supplied with chlorinated drinking water.
49 Sixty percent of the isolates belonged
to a group of four PFGE (with XbaI) profiles that were present in each of eight pens throughout the
sampling period. These investigators suggested that the farm environment is a potential reservoir of
this organism. Of 9122 cattle fecal samples examined in the state of Washington, 1.01% were positive
for E. coli 0157:H7,
72 while from 589 bovine fecal samples at the time of slaughter in Scotland, the
animal-level prevalence was estimated to be 7.5%.
65 In the latter study, 44 infected cattle contained
E. coli 0157:H7 at levels >10
4 /g.
Human Disease Syndromes/Prevalence
The prototype strain for the syndromes below is EC O157:H7. The H7 type was initially isolated in
1944 from a human diarrheal specimen, whereas the O157 type was first isolated and named in 1972
from diarrheal swine feces.
66 However, the first O157:H7 strain was recovered in 1975 from a patient
with bloody diarrhea. Stx-producing strains of E. coli were identified in 1977 in the United States
61 and
Canada
44 . Following its original isolation in 1975, the next recorded isolation of EC O157:H7 was in
1978, when it was recovered from diarrheal stools in Canada.
HUS and HC are caused by Stx-producing strains of E. coli. It has been estimated that from 2 to 7% of
infections by EC O157:H7 will develop HUS.
31 HUS consists of hemolytic anemia, thrombocytopenia,
and acute renal failure. Although not directly linked to EHEC strains until 1985, HUS was first
described in 1955. In a German study on the duration of shedding of EC O157:H7 in 53 children, the
28 children who had HC diarrhea shed the organism between 2 and 62 days (median of 13), whereas
the 25 who developed HUS shed organisms for 5–124 days (median of 21).
42 HUS is associated more
with strains that produce Stx2 alone than with those that produce Stx1, or Stx1 and Stx2
67 (see Chapter
22). Fifteen percent of 1275 individuals from which EHEC-positive cultures were recovered in the
United Kingdom for the 3-year period 1989–1991 were reported as having developed HUS.
83
Hemorrhagic colitis as a foodborne disease was first seen in 1982 in Oregon and Michigan, where
in both instances victims had eaten sandwiches at a fast-food restaurant that contained undercooked
ground beef.
73 Of 43 patients, all had bloody diarrhea and severe abdominal cramps, with 63%
experiencing nausea, 49% vomiting, but only 7% fever. The mean incubation period was 3.8–3.9
days, and symptoms lasted for 3 to more than 7 days.
73 From other outbreaks, the time of onset of
symptoms ranged between 3.1 and 8 days. The recovery of the etiological agent from stools requires
examination of specimens within several days after symptoms. Stools tend to be negative for 7 or
more days after onset of illness.
94 The bloody red stool is the telltale symptom for this syndrome and
it reflects involvement of the etiological agent in the colon. Fever is rare, and the infectious dose is
believed to be as low as 10 cfu.
Many of the reported outbreaks and cases of HC associated with food and water are summarized in
Table 27–2. Although most were caused by E. coli O157:H7, the 1993 outbreaks in New Hampshire
and Rhode Island that were traced to raw salads were caused by serotype O6:NM (NM = nonmotile).
The first established foodborne outbreak of an Stx-producer other than E. coli O157:H7 in the United
States was serotype O104:H21, which was traced to contaminated pasteurized milk in 1994.
13 Serotype
0111:NM was traced to semidry fermented sausage in South Australia in 1995, and in 1992 the same
serotype was the first ever Stx-producing strain associated with HUS in Italy when nine cases with
one death occurred.
10
645
acid-resistant numbers decreased following a brief period of hay feeding (Figure 27–2). The association
of acid resistance with virulence in some enteropathogens is discussed in Chapter 22.
From a study of E. coli 0157:H7 in fecal samples of commercial feedlot cattle in 2000 from 20
feedlot pens, 636 of 4790 samples (13%) were positive for this organism with the highest prevalence
being in 10 pens supplied with chlorinated drinking water.
49 Sixty percent of the isolates belonged
to a group of four PFGE (with XbaI) profiles that were present in each of eight pens throughout the
sampling period. These investigators suggested that the farm environment is a potential reservoir of
this organism. Of 9122 cattle fecal samples examined in the state of Washington, 1.01% were positive
for E. coli 0157:H7,
72 while from 589 bovine fecal samples at the time of slaughter in Scotland, the
animal-level prevalence was estimated to be 7.5%.
65 In the latter study, 44 infected cattle contained
E. coli 0157:H7 at levels >10
4 /g.
Human Disease Syndromes/Prevalence
The prototype strain for the syndromes below is EC O157:H7. The H7 type was initially isolated in
1944 from a human diarrheal specimen, whereas the O157 type was first isolated and named in 1972
from diarrheal swine feces.
66 However, the first O157:H7 strain was recovered in 1975 from a patient
with bloody diarrhea. Stx-producing strains of E. coli were identified in 1977 in the United States
61 and
Canada
44 . Following its original isolation in 1975, the next recorded isolation of EC O157:H7 was in
1978, when it was recovered from diarrheal stools in Canada.
HUS and HC are caused by Stx-producing strains of E. coli. It has been estimated that from 2 to 7% of
infections by EC O157:H7 will develop HUS.
31 HUS consists of hemolytic anemia, thrombocytopenia,
and acute renal failure. Although not directly linked to EHEC strains until 1985, HUS was first
described in 1955. In a German study on the duration of shedding of EC O157:H7 in 53 children, the
28 children who had HC diarrhea shed the organism between 2 and 62 days (median of 13), whereas
the 25 who developed HUS shed organisms for 5–124 days (median of 21).
42 HUS is associated more
with strains that produce Stx2 alone than with those that produce Stx1, or Stx1 and Stx2
67 (see Chapter
22). Fifteen percent of 1275 individuals from which EHEC-positive cultures were recovered in the
United Kingdom for the 3-year period 1989–1991 were reported as having developed HUS.
83
Hemorrhagic colitis as a foodborne disease was first seen in 1982 in Oregon and Michigan, where
in both instances victims had eaten sandwiches at a fast-food restaurant that contained undercooked
ground beef.
73 Of 43 patients, all had bloody diarrhea and severe abdominal cramps, with 63%
experiencing nausea, 49% vomiting, but only 7% fever. The mean incubation period was 3.8–3.9
days, and symptoms lasted for 3 to more than 7 days.
73 From other outbreaks, the time of onset of
symptoms ranged between 3.1 and 8 days. The recovery of the etiological agent from stools requires
examination of specimens within several days after symptoms. Stools tend to be negative for 7 or
more days after onset of illness.
94 The bloody red stool is the telltale symptom for this syndrome and
it reflects involvement of the etiological agent in the colon. Fever is rare, and the infectious dose is
believed to be as low as 10 cfu.
Many of the reported outbreaks and cases of HC associated with food and water are summarized in
Table 27–2. Although most were caused by E. coli O157:H7, the 1993 outbreaks in New Hampshire
and Rhode Island that were traced to raw salads were caused by serotype O6:NM (NM = nonmotile).
The first established foodborne outbreak of an Stx-producer other than E. coli O157:H7 in the United
States was serotype O104:H21, which was traced to contaminated pasteurized milk in 1994.
13 Serotype
0111:NM was traced to semidry fermented sausage in South Australia in 1995, and in 1992 the same
serotype was the first ever Stx-producing strain associated with HUS in Italy when nine cases with
one death occurred.
10