Fundamental Food Microbiology, Third Edition - Fuad Fathir

FOODBORNE TOXICOINFECTIONS 401
three had severe leg cramps. 11 The symptoms developed 1 to 6 d after consuming
the crabmeat. The stool samples of some patients yielded Vib. cholerae 01, 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 U.S. 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 crabmeat at
nonrefrigerated temperature to reach the high population necessary to cause the
disease. Other possibilities include postheat 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 harvest of crabs from contaminated water, proper
time and temperature of cooking the crabs, proper sanitation in preparing crabmeat,
refrigerating crabmeat following picking, heat treatment before preparing salad —
any one or more of these steps could have been used to avoid this incident. (Note:
It is illegal to bring food into the U.S. from other countries without prior permission
of regulatory agencies.)
A. Importance
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V. ESCHERICHIA COLI GASTROENTERITIS
The two (of the four) enteropathogenic Esc. coli subgroups that correlate well with
toxicoinfection probably belong to the enteropathogenic and enterotoxigenic Esc.
coli (EPEC and ETEC, respectively) types. They produce diarrheal diseases when
ingested in large numbers through contaminated foods and water. The symptoms
are more like those in cholera. The incidence is high in many developing countries
and is directly related to poor sanitation.
B. Characteristics
Many serotypes in both subgroups are involved in human gastroenteritis. They are
Gram-negative small curved rods, nonsporulating and motile (nonmotile strains can
be present). The strains are facultative anaerobes and can grow effectively in both
simple and complex media and many foods. Growth occurs between 10 and 50�C,
with optimum at 30 to 37�C. Some strains can grow below 10�C. Rapid growth
occurs under optimum conditions. Growth-limiting factors are low pH (below 5.0)
and low A w (below 0.93). The cells are sensitive to low-heat treatment, such as
pasteurization.