Foodborne Bacterial Infections ◾ 349
and others. The fatality rate among fetuses, infected newborn infants, and immunocompromised
individuals is very high.
Food Association
Foodborne listeriosis in humans is mainly sporadic; however, outbreaks were reported from the
consumption of contaminated coleslaw, pasteurized milk, raw milk and dairy products, soft
cheeses (Mexican style, Brie, and Liederkranz), meat pâté, turkey franks, cold cut meats, improperly cooked chicken, and smoked mussels. Fruits and vegetables, including celery and cantaloupes,
are involved in recent fatal outbreaks in the United States. Sporadic listeriosis was also documented
from the consumption of these foods either at home or at delicatessen counters. Heat-treated foods
were either not properly heated or were contaminated following heating. As many raw foods of
both animal and plant origin harbor Lis. monocytogenes, consumption of raw foods or recontaminated heat-processed foods have been the cause of listeriosis. Growth during long refrigerated
storage and temperature abuse prior to eating has been implicated in many cases. Individuals that
suffered most from listeriosis and fatality from the disease were the sensitive groups.
Prevention and Control
Because of the ubiquitous presence of Lis. monocytogenes, it is impossible to have foods free of this
pathogen. However, a strong Listeria control program at the commercial production facilities has
been imposed by the regulatory agencies and industries in many countries. This has helped to
greatly reduce the number of listeriosis cases since 1991. However, in recent years, there has been
an increase in incidents of sporadic and outbreaks of listeriosis as well as in product recalls. In
1999, there were a total of 24 recalls. In the United States, this includes the absence of Lis. monocytogenes in 25-g portions of cooked, ready-to-eat meat and poultry products from each lot; a positive lot is considered adulterated and discarded. A plant producing contaminated products is then
thoroughly tested and subjected to proper sanitation (hazard analysis critical control point; see
Appendix C) until products free of Lis. monocytogenes are produced. Because of the effectiveness
of the current regulatory procedures, there is a possibility that, in the future, the current stringent
zero tolerance may be slightly relaxed.
In addition to the control measures in the processing facilities, regulatory agencies have implicated consumer education to reduce foodborne listeriosis. This includes thoroughly cooking raw
foods of animal origin; thoroughly washing raw vegetables and fruits before eating; keeping
uncooked meats separate from vegetables, cooked foods, and ready-to-eat foods; not consuming raw milk or foods made with raw milk; and washing hands, knives, and cutting boards after
handling uncooked foods.
The Food and Drug Administration (FDA) conducted a risk assessment study in 2003 for Lis.
monocytogenes with several foods to provide a better guideline and warning to the high risk populations. They analyzed large numbers of ready-to-eat foods and categorized them into five major
groups based on their potential associated risks: very high, high, moderate risk, low, and very low
risk foods (Table 26.5).
In addition, special recommendations have been provided to high-risk individuals 16 : avoid soft
cheeses (Mexican style, feta, Brie, Camembert, blue-veined, cream, or cottage cheeses); reheat
(until steaming) all refrigerated leftover foods and ready-to-eat foods before eating; and pregnant
women, elderly people, and immunocompromised people should avoid foods from the delicatessen.
and others. The fatality rate among fetuses, infected newborn infants, and immunocompromised
individuals is very high.
Food Association
Foodborne listeriosis in humans is mainly sporadic; however, outbreaks were reported from the
consumption of contaminated coleslaw, pasteurized milk, raw milk and dairy products, soft
cheeses (Mexican style, Brie, and Liederkranz), meat pâté, turkey franks, cold cut meats, improperly cooked chicken, and smoked mussels. Fruits and vegetables, including celery and cantaloupes,
are involved in recent fatal outbreaks in the United States. Sporadic listeriosis was also documented
from the consumption of these foods either at home or at delicatessen counters. Heat-treated foods
were either not properly heated or were contaminated following heating. As many raw foods of
both animal and plant origin harbor Lis. monocytogenes, consumption of raw foods or recontaminated heat-processed foods have been the cause of listeriosis. Growth during long refrigerated
storage and temperature abuse prior to eating has been implicated in many cases. Individuals that
suffered most from listeriosis and fatality from the disease were the sensitive groups.
Prevention and Control
Because of the ubiquitous presence of Lis. monocytogenes, it is impossible to have foods free of this
pathogen. However, a strong Listeria control program at the commercial production facilities has
been imposed by the regulatory agencies and industries in many countries. This has helped to
greatly reduce the number of listeriosis cases since 1991. However, in recent years, there has been
an increase in incidents of sporadic and outbreaks of listeriosis as well as in product recalls. In
1999, there were a total of 24 recalls. In the United States, this includes the absence of Lis. monocytogenes in 25-g portions of cooked, ready-to-eat meat and poultry products from each lot; a positive lot is considered adulterated and discarded. A plant producing contaminated products is then
thoroughly tested and subjected to proper sanitation (hazard analysis critical control point; see
Appendix C) until products free of Lis. monocytogenes are produced. Because of the effectiveness
of the current regulatory procedures, there is a possibility that, in the future, the current stringent
zero tolerance may be slightly relaxed.
In addition to the control measures in the processing facilities, regulatory agencies have implicated consumer education to reduce foodborne listeriosis. This includes thoroughly cooking raw
foods of animal origin; thoroughly washing raw vegetables and fruits before eating; keeping
uncooked meats separate from vegetables, cooked foods, and ready-to-eat foods; not consuming raw milk or foods made with raw milk; and washing hands, knives, and cutting boards after
handling uncooked foods.
The Food and Drug Administration (FDA) conducted a risk assessment study in 2003 for Lis.
monocytogenes with several foods to provide a better guideline and warning to the high risk populations. They analyzed large numbers of ready-to-eat foods and categorized them into five major
groups based on their potential associated risks: very high, high, moderate risk, low, and very low
risk foods (Table 26.5).
In addition, special recommendations have been provided to high-risk individuals 16 : avoid soft
cheeses (Mexican style, feta, Brie, Camembert, blue-veined, cream, or cottage cheeses); reheat
(until steaming) all refrigerated leftover foods and ready-to-eat foods before eating; and pregnant
women, elderly people, and immunocompromised people should avoid foods from the delicatessen.