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Clinical
Symptoms
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S.t. DT104 is diagnosed by fecal testing. S. t. DT104 infection should be considered in any patient with moderate to severe gastroenteritis, especially if fever and headache are present. Diagnosis may also be made though a positive blood culture. Tests for identification of this organism include culturing for Salmonella, serotyping of Salmonella isolates to determine if they are typhimurium, phagetyping, and antibiograms to determine the pattern of antibiotic resistance.
Other, more molecular-based diagnostic tools such as plasmid
profile analysis, pulsed field gel electrophoresis (PFGE),
and polymerase chain reaction (PCR), are also important in
identifying S.t. DT104. PCR which requires minute amounts
of DNA, has been used to subtype S. typhimurium isolates
in preliminary experiments and may prove to be vital in the
diagnosis of carrier individuals, both human and animal. Initial
reports indicate that these methods hold great potential for
fast , accurate diagnosis of S.t. DT104 in acute outbreaks
as well as in herd monitoring/screening programs. These molecular
tests are only available in reference laboratories.
S.t. DT104 infections in healthy persons are usually self-limited and management consists of supportive medical care (fluid and electrolyte replacement). Antibiotics are reserved for treatment of severely ill persons who have systemic (septicemic) disease.
The common antibiotics used for treating Salmonella infections
cannot be used for people infected with S.t. DT104 because
this strain is resistant to five commonly used antibiotics
(ampicillin, chloramphenicol, streptomycin, sulfonamides,
and tetracycline). Fluoroquinolones are the drugs of first
choice for bacteremia and serious intestinal infection. However,
recent reports from Denmark and UK have suggested increasing
resistance of S.t. DT104 to fluoroquinolones (ciprofloxacin)
related to the use of this antibiotic for the treatment of
Salmonellosis in farm animals. This will pose further problems
for treating this infection especially in patients with underlying
health problems.
Although not all cases of S.t. DT104 infections are reported, and precise information on the incidence is not available, several countries have reported significant increases during the last several years. The clinical features associated with infection with S.t. DT104 may be more severe than other Salmonella infections. In a study in the United Kingdom of 83 cases of S.t. DT104 infection, 3% died, compared to a case-fatality rate for non-typhoid Salmonella infections of approximately 0.1%.
In the U.S., infections caused by multi-resistant strains
of S. t DT104 were more likely to cause bacteremia and were
associated with longer hospitalization. In the UK, there was
a ten-fold increase in the number of human cases caused by
this multi-drug resistant strain over a six year period (1990-1996).
There has also been an increase in the number of isolates
with additional resistance to trimethoprim and ciprofloxacin.
These strains have been associated with hospitalization rates
twice that of other salmonella infections and with ten times
higher case-fatality rates. In a report from British Columbia,
Canada, it was shown that the highest incidence rate of case
persons with S.t. DT104 was in the 1-4 year old age group.