620 Modern Food Microbiology
highest body temperature, and has the highest mortality rate. S. Typhi may be isolated from blood
and sometimes the stool and urine of victims prior to enteric fever. The paratyphoid syndrome
is milder than that of typhoid.
2. The host-adapted serovars (some of which are human pathogens and may be contracted from
foods): Included are S. Gallinarum (poultry), S. Dublin (cattle), S. Abortus-equi (horses), S.
Abortus-ovis (sheep), and S. Choleraesuis (swine).
3. Unadapted serovars (no host preference): These are pathogenic for humans and other animals,
and they include most foodborne serovars. The foodborne salmonellosis syndrome is described
in a later section.
Serotyping of Salmonella
The serotyping of Gram-negative bacteria is described in Chapter 11. When applied to the salmonellae, species and serovars are placed in groups designated A, B, C, and so on, according to similarities
in content of one or more O antigens. Thus, S. Hirschfeldii, S. Choleraesuis, S. Oranienburg, and S.
Montevideo are placed in group C 1 because they all have O antigens 6 and 7 in common. S. Newport is
placed in group C 2 due to its possession of O antigens K and 8 (Table 26–1). For further classification,
the flagellar or H antigens are employed. These antigens are of two types: specific phase or phase 1,
and group phase or phase 2. Phase 1 antigens are shared with only a few other species or varieties
of Salmonella; phase 2 may be more widely distributed among several species. Any given culture of
Salmonella may consist of organisms in only one phase or of organisms in both flagellar phases. The
H antigens of phase 1 are designated with small letters, and those of phase 2 are designated by arabic
numerals. Thus, the complete antigenic analysis of S. Choleraesuis is as follows: 6, 7, c, 1, 5, where
6 and 7 refer to O antigens, c to phase-1 flagellar antigens, and 1 and 5 to phase-2 flagellar antigens
(Table 26–1). Salmonella subgroups of this type are referred to as serovars. With a relatively small
number of O, phase 1, and phase 2 antigens, a large number of permutations are possible, allowing
for the possibility of a large number of serovars.***
The naming of Salmonella is done by international agreement. Under this system, a serovar is named
after the place where it was first isolated—S. London, S. Miami, S. Richmond, and so on. Prior to
the adoption of this convention, species and subtypes were named in various ways—for example, S.
Typhimurium as the cause of typhoid fever in mice.
S. Typhimurium definitive type 104 (DT104) is characterized by its resistance to five
antimicrobials—amipicillin, chloramphenicol, streptomycin, sulfa drugs, and tetracyclines (the ACSSuT profile). It was first seen in the United Kingdom in 1984. In 1990 it represented about 7% of
Typhimurium strains, about 28% in 1995, and 32% of human isolates in 1996. In addition to the
antimicrobials noted, DT104 has acquired resistance to trimethoprim and the fluoroquinolones.
Distribution
The primary habitat of Salmonella spp. is the intestinal tract of animals such as birds, reptiles,
farm animals, humans, and occasionally insects. Although their primary habitat is the intestinal tract,
they may be found in other parts of the body from time to time. As intestinal forms, the organisms
are excreted in feces from which they may be transmitted by insects and other living creatures to
a large number of places. As intestinal forms, they may also be found in water, especially polluted
water. When polluted water and foods that have been contaminated by insects or by other means are
consumed by humans and other animals, these organisms are once again shed through fecal matter
highest body temperature, and has the highest mortality rate. S. Typhi may be isolated from blood
and sometimes the stool and urine of victims prior to enteric fever. The paratyphoid syndrome
is milder than that of typhoid.
2. The host-adapted serovars (some of which are human pathogens and may be contracted from
foods): Included are S. Gallinarum (poultry), S. Dublin (cattle), S. Abortus-equi (horses), S.
Abortus-ovis (sheep), and S. Choleraesuis (swine).
3. Unadapted serovars (no host preference): These are pathogenic for humans and other animals,
and they include most foodborne serovars. The foodborne salmonellosis syndrome is described
in a later section.
Serotyping of Salmonella
The serotyping of Gram-negative bacteria is described in Chapter 11. When applied to the salmonellae, species and serovars are placed in groups designated A, B, C, and so on, according to similarities
in content of one or more O antigens. Thus, S. Hirschfeldii, S. Choleraesuis, S. Oranienburg, and S.
Montevideo are placed in group C 1 because they all have O antigens 6 and 7 in common. S. Newport is
placed in group C 2 due to its possession of O antigens K and 8 (Table 26–1). For further classification,
the flagellar or H antigens are employed. These antigens are of two types: specific phase or phase 1,
and group phase or phase 2. Phase 1 antigens are shared with only a few other species or varieties
of Salmonella; phase 2 may be more widely distributed among several species. Any given culture of
Salmonella may consist of organisms in only one phase or of organisms in both flagellar phases. The
H antigens of phase 1 are designated with small letters, and those of phase 2 are designated by arabic
numerals. Thus, the complete antigenic analysis of S. Choleraesuis is as follows: 6, 7, c, 1, 5, where
6 and 7 refer to O antigens, c to phase-1 flagellar antigens, and 1 and 5 to phase-2 flagellar antigens
(Table 26–1). Salmonella subgroups of this type are referred to as serovars. With a relatively small
number of O, phase 1, and phase 2 antigens, a large number of permutations are possible, allowing
for the possibility of a large number of serovars.***
The naming of Salmonella is done by international agreement. Under this system, a serovar is named
after the place where it was first isolated—S. London, S. Miami, S. Richmond, and so on. Prior to
the adoption of this convention, species and subtypes were named in various ways—for example, S.
Typhimurium as the cause of typhoid fever in mice.
S. Typhimurium definitive type 104 (DT104) is characterized by its resistance to five
antimicrobials—amipicillin, chloramphenicol, streptomycin, sulfa drugs, and tetracyclines (the ACSSuT profile). It was first seen in the United Kingdom in 1984. In 1990 it represented about 7% of
Typhimurium strains, about 28% in 1995, and 32% of human isolates in 1996. In addition to the
antimicrobials noted, DT104 has acquired resistance to trimethoprim and the fluoroquinolones.
Distribution
The primary habitat of Salmonella spp. is the intestinal tract of animals such as birds, reptiles,
farm animals, humans, and occasionally insects. Although their primary habitat is the intestinal tract,
they may be found in other parts of the body from time to time. As intestinal forms, the organisms
are excreted in feces from which they may be transmitted by insects and other living creatures to
a large number of places. As intestinal forms, they may also be found in water, especially polluted
water. When polluted water and foods that have been contaminated by insects or by other means are
consumed by humans and other animals, these organisms are once again shed through fecal matter