Microbial Hazards in Foods: Food-Borne Infections and Intoxications 489and no distribution to other organs. Symptoms
of salmonelosis occur 12 to 24 hours after
ingestion of food containing 1 to 10 million
Salmonella per gram and include nausea,
vomiting, headache, chills, diarrhea, and
fever. The illness lasts for 2 to 3 days. Most
patients recover; however, death can occur in
the very old, the very young, and those with
compromised immune systems.
Since no Salmonella is allowed in cooked
food for interstate commerce and interna-
tional trade, the detection of Salmonella has
been a subject of much research and
development.
Detection of Salmonella by the classical
method includes pre - enrichment of culture
from food samples, enrichment or selective
enrichment of the liquid culture, plating of
liquid on selective agar to isolate cultures,
biochemical tests of suspect colonies, and
confi rmation of isolates with typical bio-
chemical profi les by serological tests. These
procedures may take up to 5 days for comple-
tion. Recently, a variety of methods and pro-
cedures have been developed and implemented
for the effective isolation, enumeration,
detection, identifi cation, and characterization
of Salmonella. Improvement of pre - enrich-
ment and enrichment procedures has been
made by manipulating incubation tempera-
ture (using 42 ° C instead of 37 ° C), adding
various stimulation compounds such as
Oxyrase enzyme, and concentrating cells
through immunomagnetic separation (Dynal
system). A large number of biochemical
diagnostic kits, such as API, MicroID,
Enterotube, Biolog, and Vitek, have been
developed and marketed to conveniently and
automatically identify isolates. Manual and
automated sandwich ELISA tests by EIA
Assurance test, VIDAS, Tecra, etc., and
lateral immunomigration tests kits by
BioControl VIP system and Neogen have
been used widely. In terms of genetic tests,
DNA/RNA probes system by Genetrak, PCR
test by Perkin - Elmer, Probelia, BAX system
and ribotyping by Qualicon system, andpolyvalent anti - H antiserum (against fl agella
antigens).
This genus went through several revisions
in classifi cation and taxonomy of species
and subspecies in the past 20 years, due to
the advancement of genetic typing systems.
Currently, there are two species, namely,
S. enterica with six subspecies and 2,356
serovars, and S. bongori with 19 serovars.
Each serovar is potentially pathogenic. In
the literature, many scientists still use the
traditional genus and species nomenclature,
such as S. typhimurium, S. typhosa, etc. The
current accurate way to present Salmonella
in the literature is to use, for example,
“ Salmonella enterica serovar Typhimurium. ”
Note that the word “ Typhimurium ” is NOT
italicized. When used in a short version
the proper way is to spell it as follows:
Salmonella Typhimurium. This is different
from the traditional way of spelling, which
would be “ Salmonella typhimurium ”
(italicized and not capitalized for the fi rst
letter).
Salmonella has been found in water, ice,
milk, dairy products, shellfi sh, poultry and
poultry meat products, eggs and egg prod-
ucts, animal feed, and pets. Human beings
can be healthy carriers of this organism. It
has been estimated that 4% of the general
public carries this organism, with more
females than males being healthy carriers.
There are actually three types of diseases
caused by Salmonell a: enteric fever caused
by S. Typhosa (typhoid fever), in which the
organism, ingested along with food, fi nds its
way into the bloodstream, disseminates to the
kidney, and is excreted in the stools; septice-
mia caused by S. Cholerasuis, in which the
organism causes blood poisoning; and gas-
troenteritis caused by S. Typhimurium and S.
Enteritidis, a true food - borne infection. In the
last case, large numbers of live Salmonella
are ingested with food; in 1 to 3 days, they
liberate the endotoxins, which cause local-
ized violent irritation of the mucous mem-
brane, with no invasion of the bloodstream