Foodborne Bacterial Infections ◾ 353
recognized from the consumption of imported Camembert cheese contaminated with serotype
O124:H17. The pathogens produce virulence factors that are responsible for invasion to epithelial
cells and enable the pathogen to move from cell to cell and set up infection in the colon. The genes
for invasion are encoded in a 140-MDa plasmid. 23
Disease and Symptoms
The disease and symptoms are like shigellosis. Following ingestion of the pathogen (about 10 6 cells) and
an incubation period, symptoms appear as abdominal cramps, profuse diarrhea, headache, chills, and
fever. A large number of pathogens are excreted in the feces. The symptoms can last for 7–12 days, but
a person can remain a carrier and shed the pathogens in feces for a long time. 23
Food Association
Only humans are known to be the host of the pathogen, and a food can get contaminated directly
or indirectly though fecal contamination. Outbreaks from the ingestion of foods contaminated
with this pathogen have been recorded. The 1971 outbreak in the United States from the ingestion of an imported cheese was traced to contamination of the processing plant equipment from a
malfunctioning water filtration system. In 1983, another outbreak on a cruise ship was related to
potato salad contaminated by a carrier food handler.
Prevention
The pathogen is sensitive to pasteurization temperatures. Thus, proper heat treatment, elimination
of post-heat contamination for a ready-to-eat food, and refrigeration of a food soon after preparation are necessary to control the disease. In addition, proper sanitation at all stages of food processing and handling will be an important factor. Finally, individuals suspected of being carriers
should not handle food, especially ready-to-eat food.
Enteroaggregative Escherichia coli
EAEC causes diarrhea in children and adults, lasting more than 14 days and is prevalent in developing countries. The diarrhea in children is similar to ETEC and causes mild but significant
mucosal damage. During infection, it expresses aggregative adherence fimbriae that help bacteria
to form characteristic stacked brick–like aggregates on the intestinal cells and causes mucosal
damage. In addition, it produces two types of toxins: EAST (enteroaggregative heat stable toxin)
and a hemolysin, which form pores. Generally, EAEC do not produce Shiga toxin, but a new
EAEC serovar (O104:H4) has emerged in 2011 that expresses Stx and caused disease similar to
EHEC (see below) and was responsible for the largest outbreak in Germany from consumption of
sprouts affecting 3842 people with 53 deaths (see Chapter 29).
Enterohemorrhagic Escherichia coli (EHEC),
Shiga- Toxigenic Escherichia coli (STEC) 24
The strains in this group (a principal serogroup is O157:H7) have been recognized relatively
recently (1982) as the cause of severe bloody diarrhea (hemorrhagic colitis) and hemorrhagic uremic syndrome (HUS) in humans. Other serogroups in EHEC are O157:NM and less common
recognized from the consumption of imported Camembert cheese contaminated with serotype
O124:H17. The pathogens produce virulence factors that are responsible for invasion to epithelial
cells and enable the pathogen to move from cell to cell and set up infection in the colon. The genes
for invasion are encoded in a 140-MDa plasmid. 23
Disease and Symptoms
The disease and symptoms are like shigellosis. Following ingestion of the pathogen (about 10 6 cells) and
an incubation period, symptoms appear as abdominal cramps, profuse diarrhea, headache, chills, and
fever. A large number of pathogens are excreted in the feces. The symptoms can last for 7–12 days, but
a person can remain a carrier and shed the pathogens in feces for a long time. 23
Food Association
Only humans are known to be the host of the pathogen, and a food can get contaminated directly
or indirectly though fecal contamination. Outbreaks from the ingestion of foods contaminated
with this pathogen have been recorded. The 1971 outbreak in the United States from the ingestion of an imported cheese was traced to contamination of the processing plant equipment from a
malfunctioning water filtration system. In 1983, another outbreak on a cruise ship was related to
potato salad contaminated by a carrier food handler.
Prevention
The pathogen is sensitive to pasteurization temperatures. Thus, proper heat treatment, elimination
of post-heat contamination for a ready-to-eat food, and refrigeration of a food soon after preparation are necessary to control the disease. In addition, proper sanitation at all stages of food processing and handling will be an important factor. Finally, individuals suspected of being carriers
should not handle food, especially ready-to-eat food.
Enteroaggregative Escherichia coli
EAEC causes diarrhea in children and adults, lasting more than 14 days and is prevalent in developing countries. The diarrhea in children is similar to ETEC and causes mild but significant
mucosal damage. During infection, it expresses aggregative adherence fimbriae that help bacteria
to form characteristic stacked brick–like aggregates on the intestinal cells and causes mucosal
damage. In addition, it produces two types of toxins: EAST (enteroaggregative heat stable toxin)
and a hemolysin, which form pores. Generally, EAEC do not produce Shiga toxin, but a new
EAEC serovar (O104:H4) has emerged in 2011 that expresses Stx and caused disease similar to
EHEC (see below) and was responsible for the largest outbreak in Germany from consumption of
sprouts affecting 3842 people with 53 deaths (see Chapter 29).
Enterohemorrhagic Escherichia coli (EHEC),
Shiga- Toxigenic Escherichia coli (STEC) 24
The strains in this group (a principal serogroup is O157:H7) have been recognized relatively
recently (1982) as the cause of severe bloody diarrhea (hemorrhagic colitis) and hemorrhagic uremic syndrome (HUS) in humans. Other serogroups in EHEC are O157:NM and less common