Foodborne Bacterial Infections ◾ 343
use of sewage as fertilizer or washing products with polluted water), such as cantaloupe, tomatoes,
nuts, and seafood, such as finfish (harvested from polluted water). Recent surveys show that soil and
irrigation water are major sources for Salmonella contamination in fresh produce. 7
Although there are about 2600 serotypes of Salmonella, only a small number of them have
been frequently associated with foodborne illnesses. This could be a result of geographical distribution of the serotypes as well as the pathogenicity of a serovar or a strain. Sal. enterica ser.
Typhimurium has been associated in the United States as the major causative agent of foodborne
salmonellosis (over 20% of the total cases). However, since the 1980s, foodborne salmonellosis
from Sal. enterica ser. Enteritidis has increased, mainly from contaminated shell eggs; in recent
years, it has been involved in the same number of cases as Sal. enterica ser. Typhimurium. The
exact cause of the predominance of Sal. enterica ser. Enteritidis is not yet clearly understood. The
methods used in raising food animals and birds and in the processing of foods of animal origin
are suspected to have an important role.
Prevention and Control
Raw foods of animal origin that are heat-treated before consumption can have Salmonella.
However, in the United States (and other developed countries), as per regulatory requirements,
heat-treated and ready-to-eat foods that contain Salmonella in portions (samples) tested are considered to be adulterated and should not be sold. Many food-processing industries have in-house
Salmonella (as well as several other pathogens) surveillance programs to control the presence of
Salmonella in their products. The regulatory agencies also have programs to educate consumers
at home and food handlers in food service places to control Salmonella contamination in foods.
These include proper cooking of foods (minimum to pasteurization temperature and time, such
as 71.7°C for 15 seconds or equivalent) and prompt cooling (to 3°C–4°C or freezing, if not used
in two hours); prevention of cross-contamination of a ready-to-eat food with a raw food through
cutting boards, equipment, utensils, and hands; use of proper sanitation and personal hygiene; not
handling a food while sick; and properly reheating a food refrigerated for a long time.
Detection Method
The methods involve preenrichment of a sample of food in a nutrient broth, followed by selective
enrichment, streaking on a selective-differential agar medium, and biochemical and serological
confirmation (see Chapter 42). Several rapid methods, based on specific immunological characteristics and nucleotide base sequence in the nucleic acids, have been developed.
A Case Study
In July of 1989, 21 out of 24 people who attended a baby shower at a home in New York had
gastroenteritis with severe diarrhea, vomiting, fever, and cramps within 6–57 hours after the
party. 8 Twenty people needed medical help, of which 18 were hospitalized with one at 38 weeks
pregnancy; the infant was delivered while she was ill and developed septicemia. Sal. enterica ser.
Enteritidis was isolated from all 21 people (rectal swab) and the infant. All 21 ill attendees, but
not the three who remained well, ate a homemade baked ziti pasta dish consisting of one raw egg,
ricotta cheese, cooked tomato, and meat sauce, mixed together in a pan and refrigerated overnight.
Before serving, the preparation was baked for 30 minutes at 350°F (176.7°C). Several attendees
commented that the center of the ziti was cold when served. Sal. enterica ser. Enteritidis was
use of sewage as fertilizer or washing products with polluted water), such as cantaloupe, tomatoes,
nuts, and seafood, such as finfish (harvested from polluted water). Recent surveys show that soil and
irrigation water are major sources for Salmonella contamination in fresh produce. 7
Although there are about 2600 serotypes of Salmonella, only a small number of them have
been frequently associated with foodborne illnesses. This could be a result of geographical distribution of the serotypes as well as the pathogenicity of a serovar or a strain. Sal. enterica ser.
Typhimurium has been associated in the United States as the major causative agent of foodborne
salmonellosis (over 20% of the total cases). However, since the 1980s, foodborne salmonellosis
from Sal. enterica ser. Enteritidis has increased, mainly from contaminated shell eggs; in recent
years, it has been involved in the same number of cases as Sal. enterica ser. Typhimurium. The
exact cause of the predominance of Sal. enterica ser. Enteritidis is not yet clearly understood. The
methods used in raising food animals and birds and in the processing of foods of animal origin
are suspected to have an important role.
Prevention and Control
Raw foods of animal origin that are heat-treated before consumption can have Salmonella.
However, in the United States (and other developed countries), as per regulatory requirements,
heat-treated and ready-to-eat foods that contain Salmonella in portions (samples) tested are considered to be adulterated and should not be sold. Many food-processing industries have in-house
Salmonella (as well as several other pathogens) surveillance programs to control the presence of
Salmonella in their products. The regulatory agencies also have programs to educate consumers
at home and food handlers in food service places to control Salmonella contamination in foods.
These include proper cooking of foods (minimum to pasteurization temperature and time, such
as 71.7°C for 15 seconds or equivalent) and prompt cooling (to 3°C–4°C or freezing, if not used
in two hours); prevention of cross-contamination of a ready-to-eat food with a raw food through
cutting boards, equipment, utensils, and hands; use of proper sanitation and personal hygiene; not
handling a food while sick; and properly reheating a food refrigerated for a long time.
Detection Method
The methods involve preenrichment of a sample of food in a nutrient broth, followed by selective
enrichment, streaking on a selective-differential agar medium, and biochemical and serological
confirmation (see Chapter 42). Several rapid methods, based on specific immunological characteristics and nucleotide base sequence in the nucleic acids, have been developed.
A Case Study
In July of 1989, 21 out of 24 people who attended a baby shower at a home in New York had
gastroenteritis with severe diarrhea, vomiting, fever, and cramps within 6–57 hours after the
party. 8 Twenty people needed medical help, of which 18 were hospitalized with one at 38 weeks
pregnancy; the infant was delivered while she was ill and developed septicemia. Sal. enterica ser.
Enteritidis was isolated from all 21 people (rectal swab) and the infant. All 21 ill attendees, but
not the three who remained well, ate a homemade baked ziti pasta dish consisting of one raw egg,
ricotta cheese, cooked tomato, and meat sauce, mixed together in a pan and refrigerated overnight.
Before serving, the preparation was baked for 30 minutes at 350°F (176.7°C). Several attendees
commented that the center of the ziti was cold when served. Sal. enterica ser. Enteritidis was