Food Biochemistry and Food Processing

692 Part VII: Food Safety

illness. It is believed that the number of reported
outbreaks represents only 10% of the real incidence
of foodborne disease, even in countries with well-
established surveillance systems (Baird-Parker 2000).
Foodborne illness resulting from severe infections
such as hemolytic uremic syndrome, botulism, and
listeriosis often require hospitalization and are more
likely to be reported, while self-limiting foodborne
illness such as salmonellosis, campylobacteriosis,
and S. aureusenterotoxin–related infections are less
likely to be reported. It is believed that viral food-
borne infections account for a large portion of cases
of foodborne illness (Caul 2000). However, the
extent of the problem on a global scale is difficult to
assess as a result of lack of surveillance data in most
parts of the world, coupled with the fact that most
viral infections are self-limiting. Although viruses
and bacteria-related infections account for the
majority of foodborne diseases, certain groups of
parasites and fungi are also etiologic agents of food-
borne diseases.

FOODBORNEBACTERIALINFECTIONS

Several types of foodborne bacterial pathogens are
implicated in foodborne diseases. Examples of bac-
terial genera most commonly implicated in food-
borne infections, onset and duration of the symp-

toms of the disease, types of foods that are likely to

be contaminated by these groups of bacteria, and

potential sources of contamination are summarized

in Table 30.1. Bacterial pathogens including Camp-

ylobacter, Salmonella, Listeria monocytogenesand

verocytotoxigenic E. coliare the top causes of bac-

terial foodborne infections in westernized countries,

based on the number of reported cases (Sharp and

Reilly 2000). The number of reported cases of Sal-

monella, Campylobacterand E. coliO157 increased

from 2- to 40-fold between 1982 and 1994 (Sharp

and Reilly 2000). The increase in the number of cas-

es was attributed to heightened awareness of food-

borne related illness, improved diagnostic methods,

and improved reporting and surveillance proce-

dures. Campylobacteris currently the leading cause

of foodborne disease in the United States and Can-

ada, followed by Salmonella-related infections. The

numbers of estimated cases of foodborne illness per

year in the United States and Canada countries are

listed in Table 30.2. Although the number of Listeria

monocytogenes–related infections is considerably

lower than those of other pathogens, foodborne

infections caused by this organism are characterized

by a high case mortality ratio, especially in certain

high risk groups such as the elderly, the young, im-

munocompromised individuals, and pregnant wo-

men. Infections caused by E. coliO157:H7 often

Figure 30.1.On-farm sources of microbial contamination of water and food products of plant and animal origin.
(Adapted from Beuchat 1995.)