Foodborne Gastroenteritis Caused by Salmonella and Shigella
629
Synopses of the three leading serotypes recovered from six different sources are presented below.
1. Retail foods in Korea (1993–2001). Of the 1,334 samples tested, 2.2% were salmonellae positive.
Most common serotypes: Enteritidis, Virginia, Haardt.
16
2. Minced beef and pork in Germany (1996–1997). Of the 1,445 samples, 6.3% were salmonellae
positive. Most common serotypes: Typhimurium, Derby, Typhimurium var. Copenhagen.
53
3. Human food and beverages in Singapore (1998). Of the 2,617 samples, 1.4% were salmonellae
positive. Most common serotypes: Typhimurium, Agona, and Dumfries and Enteritidis.
41
4. Hen layer feed in Japan (1993–1998). Of 10,418 samples, 0.5% were salmonellae positive. Most
common: Untypable, Eastbourne, Orion.
49
5. Feedlot cattle feces in the United States (1996). Of the 4,977 samples, 5.5% were salmonellae
positive. Most common: Anatum, Montevideo, Muenster.
20
6. Beef cow feces in the United States (1998). Three most common serotypes: Oranienburg, Cerro,
Anatum.
19
Prevention and Control of Salmonellosis
The intestinal tract of humans and other animals is the primary reservoir of the etiological agents.
Animal fecal matter is of greater importance than human, and animal hides may become contaminated
from the fecal source. Salmonella spp. are maintained within an animal population by means of
nonsymptomatic animal infections and in animal feeds. Both sources serve to keep slaughter animals
reinfected in a cyclical manner, although animal feeds seem less important than once believed.
Secondary contamination is another of the important sources of salmonellae in human infections.
Their presence in meats, eggs, and even air makes their presence in certain foods inevitable through
the agency of handlers and direct contact of noncontaminated foods with contaminated foods.
25
In view of the worldwide distribution of salmonellae, the ultimate control of foodborne salmonellosis
will be achieved by freeing animals and humans of the organisms. This is obviously a difficult task
but not impossible; only about 35 of the more than 2,400 serovars account for around 90% of human
isolates and approximately 80% of nonhuman isolates.
37
At the consumer level, the Salmonella carrier is thought to play a role, but just how important
this role may be is not clear. Improper preparation and handling of foods in homes and food service
establishments continue to be the primary factors in outbreaks.
With respect to the colonization of chickens by S. Enteritidis, one study used a phage type 8 strain
administered orally 10
8 to adult laying hens.
31 Within two days, the organism was found throughout the
body, including the ovary and oviduct. It was detected in some forming eggs, although its incidence was
much lower in freshly laid eggs. Investigators concluded that forming eggs are subject to descending
infection from colonized ovarian tissue, to ascending infections from colonized vaginal and cloacal
tissues, and to lateral infections from colonized upper oviduct tissues.
31 The hatchery eggs are of
critical importance because if they are contaminated, hatchlings may become infected at this early
stage. Salmonellae rapidly penetrate freshly laid fertile eggs, become entrapped in the membrane, and
may be ingested by an embryo as it emerges from the egg.
Competitive Exclusion to Reduce Salmonellae Carriage in Poultry
It is generally agreed that the primary source of salmonellae in poultry products is the gastrointestinal
tract, including the ceca. If young chicks become colonized with salmonellae, the bacteria may be shed
629
Synopses of the three leading serotypes recovered from six different sources are presented below.
1. Retail foods in Korea (1993–2001). Of the 1,334 samples tested, 2.2% were salmonellae positive.
Most common serotypes: Enteritidis, Virginia, Haardt.
16
2. Minced beef and pork in Germany (1996–1997). Of the 1,445 samples, 6.3% were salmonellae
positive. Most common serotypes: Typhimurium, Derby, Typhimurium var. Copenhagen.
53
3. Human food and beverages in Singapore (1998). Of the 2,617 samples, 1.4% were salmonellae
positive. Most common serotypes: Typhimurium, Agona, and Dumfries and Enteritidis.
41
4. Hen layer feed in Japan (1993–1998). Of 10,418 samples, 0.5% were salmonellae positive. Most
common: Untypable, Eastbourne, Orion.
49
5. Feedlot cattle feces in the United States (1996). Of the 4,977 samples, 5.5% were salmonellae
positive. Most common: Anatum, Montevideo, Muenster.
20
6. Beef cow feces in the United States (1998). Three most common serotypes: Oranienburg, Cerro,
Anatum.
19
Prevention and Control of Salmonellosis
The intestinal tract of humans and other animals is the primary reservoir of the etiological agents.
Animal fecal matter is of greater importance than human, and animal hides may become contaminated
from the fecal source. Salmonella spp. are maintained within an animal population by means of
nonsymptomatic animal infections and in animal feeds. Both sources serve to keep slaughter animals
reinfected in a cyclical manner, although animal feeds seem less important than once believed.
Secondary contamination is another of the important sources of salmonellae in human infections.
Their presence in meats, eggs, and even air makes their presence in certain foods inevitable through
the agency of handlers and direct contact of noncontaminated foods with contaminated foods.
25
In view of the worldwide distribution of salmonellae, the ultimate control of foodborne salmonellosis
will be achieved by freeing animals and humans of the organisms. This is obviously a difficult task
but not impossible; only about 35 of the more than 2,400 serovars account for around 90% of human
isolates and approximately 80% of nonhuman isolates.
37
At the consumer level, the Salmonella carrier is thought to play a role, but just how important
this role may be is not clear. Improper preparation and handling of foods in homes and food service
establishments continue to be the primary factors in outbreaks.
With respect to the colonization of chickens by S. Enteritidis, one study used a phage type 8 strain
administered orally 10
8 to adult laying hens.
31 Within two days, the organism was found throughout the
body, including the ovary and oviduct. It was detected in some forming eggs, although its incidence was
much lower in freshly laid eggs. Investigators concluded that forming eggs are subject to descending
infection from colonized ovarian tissue, to ascending infections from colonized vaginal and cloacal
tissues, and to lateral infections from colonized upper oviduct tissues.
31 The hatchery eggs are of
critical importance because if they are contaminated, hatchlings may become infected at this early
stage. Salmonellae rapidly penetrate freshly laid fertile eggs, become entrapped in the membrane, and
may be ingested by an embryo as it emerges from the egg.
Competitive Exclusion to Reduce Salmonellae Carriage in Poultry
It is generally agreed that the primary source of salmonellae in poultry products is the gastrointestinal
tract, including the ceca. If young chicks become colonized with salmonellae, the bacteria may be shed