Foodborne Toxico-Infections ◾ 381
enough to kill Vib. cholerae cells) were mainly involved. These foods were probably contaminated
with Vib. cholerae cells from the water from which they were harvested. Seafood, eaten either raw
or improperly cooked, was responsible for the incidents from South American countries too. These
foods either had Vib. cholerae when harvested or became contaminated after harvest. One of the
most important aspects of these data is to recognize how foods from one country can be involved
in a disease in another country.
Prevention
The spread of the disease can be prevented or reduced by adopting proper hygienic measures.
These include provision for properly treated municipal water, decontamination of other water by
boiling or chemical treatment, and proper disposal of sewage. The infected persons may be treated
with antibiotics to enhance recovery, along with replacing body fluids. Unexposed people can
be vaccinated to protect them from the disease. Seafood should not be harvested from polluted
water or from water found to harbor Vib. cholerae. Finally, seafoods should not be eaten raw. The
time-temperature of heat treatment of a suspected food should be enough to kill the pathogen.
An example of this is the survival of Vib. cholerae in contaminated crabs boiled for approximately
eight minutes; a 10-minute boiling time is probably necessary to ensure killing.
Detection Method
Isolation of Vib. cholerae from a sample is achieved by an initial preenrichment in alkaline peptone
water, followed by streaking on a selective agar medium plate (such as thiosulfate citrate bile salt
sucrose agar). 13 Suspected colonies (yellow) are biochemically and serologically tested for confirmation. The toxin is detected by immunoassay or bioassay (Chapter 42). The toxin gene can be
identified by PCR. 14
Analysis of an Outbreak
Between March 31 and April 3, 1991, eight people developed profuse watery diarrhea after eating crabmeat transported from Ecuador; of these, five also had vomiting and three had severe leg
cramps. The symptoms developed one to six days after consuming the crabmeat. The stool samples of some patients yielded Vib. cholerae O1, biotype El Tor, serotype Inaba (the same serotype
involved in the cholera epidemic in South American countries, including Ecuador). No crabmeat
samples were available for analysis.
Investigations revealed that the crabs were purchased at a fish market in Ecuador, then boiled,
shelled, wrapped in foil, and transported by air, unrefrigerated in a plastic bag, to the United
States on March 30. The meat was delivered to a private residence, refrigerated overnight, and
served as a salad on March 31 and April 1.
The probable sequence of events was as follows. The live crabs were contaminated with Vib.
cholerae harvested from contaminated water, and cooking was not sufficient to kill all the cells.
The viable cells subsequently grew in the crabmeat at nonrefrigerated temperatures to reach the
high population necessary to cause the disease. Other possibilities include post-heat contamination of the meat during shelling by one or more people with the disease in mild or asymptomatic
form or from the contamination of equipment or the water used. Consumption of the crabmeat
caused the disease. Preventing the harvest of crabs from contaminated water, proper time and
temperature of cooking the crabs, proper sanitation in preparing crabmeat, refrigerating crabmeat
enough to kill Vib. cholerae cells) were mainly involved. These foods were probably contaminated
with Vib. cholerae cells from the water from which they were harvested. Seafood, eaten either raw
or improperly cooked, was responsible for the incidents from South American countries too. These
foods either had Vib. cholerae when harvested or became contaminated after harvest. One of the
most important aspects of these data is to recognize how foods from one country can be involved
in a disease in another country.
Prevention
The spread of the disease can be prevented or reduced by adopting proper hygienic measures.
These include provision for properly treated municipal water, decontamination of other water by
boiling or chemical treatment, and proper disposal of sewage. The infected persons may be treated
with antibiotics to enhance recovery, along with replacing body fluids. Unexposed people can
be vaccinated to protect them from the disease. Seafood should not be harvested from polluted
water or from water found to harbor Vib. cholerae. Finally, seafoods should not be eaten raw. The
time-temperature of heat treatment of a suspected food should be enough to kill the pathogen.
An example of this is the survival of Vib. cholerae in contaminated crabs boiled for approximately
eight minutes; a 10-minute boiling time is probably necessary to ensure killing.
Detection Method
Isolation of Vib. cholerae from a sample is achieved by an initial preenrichment in alkaline peptone
water, followed by streaking on a selective agar medium plate (such as thiosulfate citrate bile salt
sucrose agar). 13 Suspected colonies (yellow) are biochemically and serologically tested for confirmation. The toxin is detected by immunoassay or bioassay (Chapter 42). The toxin gene can be
identified by PCR. 14
Analysis of an Outbreak
Between March 31 and April 3, 1991, eight people developed profuse watery diarrhea after eating crabmeat transported from Ecuador; of these, five also had vomiting and three had severe leg
cramps. The symptoms developed one to six days after consuming the crabmeat. The stool samples of some patients yielded Vib. cholerae O1, biotype El Tor, serotype Inaba (the same serotype
involved in the cholera epidemic in South American countries, including Ecuador). No crabmeat
samples were available for analysis.
Investigations revealed that the crabs were purchased at a fish market in Ecuador, then boiled,
shelled, wrapped in foil, and transported by air, unrefrigerated in a plastic bag, to the United
States on March 30. The meat was delivered to a private residence, refrigerated overnight, and
served as a salad on March 31 and April 1.
The probable sequence of events was as follows. The live crabs were contaminated with Vib.
cholerae harvested from contaminated water, and cooking was not sufficient to kill all the cells.
The viable cells subsequently grew in the crabmeat at nonrefrigerated temperatures to reach the
high population necessary to cause the disease. Other possibilities include post-heat contamination of the meat during shelling by one or more people with the disease in mild or asymptomatic
form or from the contamination of equipment or the water used. Consumption of the crabmeat
caused the disease. Preventing the harvest of crabs from contaminated water, proper time and
temperature of cooking the crabs, proper sanitation in preparing crabmeat, refrigerating crabmeat