650 Modern Food Microbiology
intracellular cyclic guanosine monophosphate (cGMP). The increased levels of mucosal cGMP lead to
loss of fluids and electrolytes. ST differs from CT in that only the particulate form of intestinal guanylate cyclase is stimulated by ST.
28 STa differs from LT in that the former stimulates guanylate cyclase,
whereas the latter and CT activate adenylate cyclase. STb elevates luminal 5-hydroxytryptamine and
prostaglandin E 2 , both of which are mediators of intestinal secretions. STb does not activate guanylate
cyclase, and genes controlling its production have been mapped
56 and subcloned from its plasmid and
sequenced.
70
The mechanisms of Shiga, Stx1, Stx2, Stx2e, and the castor bean protein, ricin, are the same. They
are N -glycosidases that cleave a specific adenine residue from the 28S subunit of eukaryotic rRNA,
leading to the inhibition of protein synthesis.
62,92
Foodborne and Waterborne Outbreaks. Some of the earliest known foodborne outbreaks caused by
ETEC and other strains are summarized in Table 27–4. Regarding the virulence groups, it may be
noted that EIEC was first confirmed as the cause of a foodborne outbreak in 1947, and the first in the
United States occurred in 1971. An EPEC strain was confirmed as the cause of a foodborne outbreak
in 1961, an ETEC in 1980, and EHEC in 1982. The first well-documented outbreak of human disease
by an ETEC was a waterborne outbreak that occurred in a national park in the state of Oregon in 1975.
There were about 2200 victims who drank improperly chlorinated water. The causative ETEC strain
was O6:H16.
PREVENTION
In general, the prevention/avoidance of foodborne illness by E. coli can be achieved by observing
the factors noted in the last section of Chapter 23. However, because of the consequences to young
children, special precautions need to be observed. The heat sensitivity of these organisms is such that
cases should not occur when foods are properly cooked. In the case of ground beef, the recommendation
is that it should be cooked to 160
◦ F (71.1
◦ C), or that the core temperature be brought to a minimum
of 155
◦ F (58.3
◦ C) for at least 15 seconds and that the juices are clear (1993 recommendation of
the U.S. Food and Drug Administration Food Code). Because of unevenness of hamburger patties,
cooking at 155–160
◦ F (58.3–71.1
◦ C) provides a measure of safety. Once cooked, hamburgers as well
as other meats should not be held between 40
◦ and 140
◦ F for more than 3–4 hours. Although the
largest recorded foodborne outbreak was associated with ground beef, all raw meat, poultry, seafood;
and some fruits and vegetables should be considered possible vehicles for hemorrhagic colitis.
TRAVELERS’ DIARRHEA
E. coli is well established as one of the leading causes of acute watery diarrhea that often occurs
among new arrivals in certain foreign countries. Among Peace Corps volunteers in rural Thailand, 57%
of 35 developed the syndrome during their first 5 weeks in the country, and 50% showed evidence of
infection by ETEC strains. In 1976, a shipboard outbreak of gastroenteritis was shown to be caused by
serotype O25:K98:NM that produced only LT. Similar strains have been recovered from other victims
of travelers’ diarrhea in various countries along with EPEC and ST-producing strains.
Among other organisms associated with this syndrome are rotaviruses, noroviruses, Entamoeba
histolytica, Yersinia enterocolitica, Giardia lamblia, Campylobacter jejuni/coli, Shigella spp. and
possibly Aeromonas hydrophila, Klebsiella pneumoniae, and Enterobacter cloacae.
intracellular cyclic guanosine monophosphate (cGMP). The increased levels of mucosal cGMP lead to
loss of fluids and electrolytes. ST differs from CT in that only the particulate form of intestinal guanylate cyclase is stimulated by ST.
28 STa differs from LT in that the former stimulates guanylate cyclase,
whereas the latter and CT activate adenylate cyclase. STb elevates luminal 5-hydroxytryptamine and
prostaglandin E 2 , both of which are mediators of intestinal secretions. STb does not activate guanylate
cyclase, and genes controlling its production have been mapped
56 and subcloned from its plasmid and
sequenced.
70
The mechanisms of Shiga, Stx1, Stx2, Stx2e, and the castor bean protein, ricin, are the same. They
are N -glycosidases that cleave a specific adenine residue from the 28S subunit of eukaryotic rRNA,
leading to the inhibition of protein synthesis.
62,92
Foodborne and Waterborne Outbreaks. Some of the earliest known foodborne outbreaks caused by
ETEC and other strains are summarized in Table 27–4. Regarding the virulence groups, it may be
noted that EIEC was first confirmed as the cause of a foodborne outbreak in 1947, and the first in the
United States occurred in 1971. An EPEC strain was confirmed as the cause of a foodborne outbreak
in 1961, an ETEC in 1980, and EHEC in 1982. The first well-documented outbreak of human disease
by an ETEC was a waterborne outbreak that occurred in a national park in the state of Oregon in 1975.
There were about 2200 victims who drank improperly chlorinated water. The causative ETEC strain
was O6:H16.
PREVENTION
In general, the prevention/avoidance of foodborne illness by E. coli can be achieved by observing
the factors noted in the last section of Chapter 23. However, because of the consequences to young
children, special precautions need to be observed. The heat sensitivity of these organisms is such that
cases should not occur when foods are properly cooked. In the case of ground beef, the recommendation
is that it should be cooked to 160
◦ F (71.1
◦ C), or that the core temperature be brought to a minimum
of 155
◦ F (58.3
◦ C) for at least 15 seconds and that the juices are clear (1993 recommendation of
the U.S. Food and Drug Administration Food Code). Because of unevenness of hamburger patties,
cooking at 155–160
◦ F (58.3–71.1
◦ C) provides a measure of safety. Once cooked, hamburgers as well
as other meats should not be held between 40
◦ and 140
◦ F for more than 3–4 hours. Although the
largest recorded foodborne outbreak was associated with ground beef, all raw meat, poultry, seafood;
and some fruits and vegetables should be considered possible vehicles for hemorrhagic colitis.
TRAVELERS’ DIARRHEA
E. coli is well established as one of the leading causes of acute watery diarrhea that often occurs
among new arrivals in certain foreign countries. Among Peace Corps volunteers in rural Thailand, 57%
of 35 developed the syndrome during their first 5 weeks in the country, and 50% showed evidence of
infection by ETEC strains. In 1976, a shipboard outbreak of gastroenteritis was shown to be caused by
serotype O25:K98:NM that produced only LT. Similar strains have been recovered from other victims
of travelers’ diarrhea in various countries along with EPEC and ST-producing strains.
Among other organisms associated with this syndrome are rotaviruses, noroviruses, Entamoeba
histolytica, Yersinia enterocolitica, Giardia lamblia, Campylobacter jejuni/coli, Shigella spp. and
possibly Aeromonas hydrophila, Klebsiella pneumoniae, and Enterobacter cloacae.