the most common use 80~90% positive during the first 2 weeks of illness
50% in 3 weeks
not easy in 4 week re-positive when relapse
attention to the use of antibiotics
The bone marrow culture
the most sensitive test specially in patients pretreated with antibiotics.
Urine and stool cultures increase the diagnostic yield positive less frequently stool culture better in 3~4 weeks
The duodenal string test to culture bile useful for the diagnosis of carriers.
Rose spots: Not use routinely
Serological tests(Vidal test): five types antigen: somatic antigen(O),flagella(H) antigen, and paratyphoid fever flagella(A,B,C) antigen.
Antibody reaction appear during first week
70% positive in 3~4 weeks and can prolong to several months
in some cases, antibodies appear slowly, or remain at a low level,
some(10~30%) not appear at all.
"O" agglutinin antibody titer ≥1:80 and "H" ≥1:160 or "O" 4 times higher supports a diagnosis of typhoid fever
"O" rises alone, not "H", early of the disease.Only "H" positive, but "O" negative, often nonspecifically elevated by immunization or previous infections or anamnestic reaction.
Antibody level maybe lower when have used antibiotics early.
Some cross reaction between group “D” and “A”.
False positive in some infectious diseases.
Some positive in blood culture ,but negative in vidal test.
'Vi" often useful for carrier
molecular biological tests: DNA probe or polymerase chain reaction (PCR)
Intestinal hemorrhage Commonly appear during the second-third week of illness difference between mild and greater bleeding often caused by unsuitable food, diarrhea et al
serious bleeding in about 2~8% a sudden drop in temperature 、 rise in pulse 、 and signs of shock followed by dark or fresh blood in the stool.
Intestinal perforation :
The more serious .Incidence,1-4%
Commonly appear during 2-3 weeks.
Take place at the lower end of ileum.
Before perforation,abdominal pain or
diarrhea,intestinal bleeding .
When perforation, abdominal pain, sweating, drop in temperature, and increase in pulse rate, then, tympanites pain when press abdomen,
abdomen muscle entasia, reduce or disappear in the sonant extent of liver, leukocytosis .
Temperature rise .peritonitis appear.
celiac free air under x-ray.
Toxic hepatitis :
hepatomegaly, ALT elevated
get better with improvement of diseases in 2~3 weeks
Toxic myocarditis .
seen in 2-3 weeks, usually severe toxemia.
seen in early stage
Other complications :
Hemolytic uremic syndrome.
acute cholecystitis 、
nephritis et al.
Typical symptoms and signs
Viral infections :
such as influenza.
abrupt onset with fever,chill,malaise, cough, coryza, and muscle aches.
cases usually in epidemic pattern,not sporadic.
differential diagnosis depends on typical manifestations and blood culture.
history of exposure to malaria.
Paroxysms(often periodic) of sequential chill,high fever and sweating.