Febrile Antigens Flashcards
stained bacterial antigen suspensions used to identify and measure antibodies following infection
febrile antigens
the bacteria cause the body to produce the antibody in response to what
pathogens created
what is the positive reaction when serum sample is mixed with a febrile antigen?
agglutination
serologic tests performed when dealing with febrile antigen
widal test, weil-felix test
specifically for the detection of antibodies from typhoid
widal test
what is the causative agent of typhoid?
salmonella enterica subsp. enterica serovar typhi
test specifically for the detection of antibodies for Rickettsial infection
Weil-Felix test
what is used in Weil-Felix test as bacterial suspension
Proteus
for the widal test, what are the 4 antigen suspensions used?
s. typhi O
s. typhi H
s. typhi BH
s. typhi AH
what is the negative control for the widal test?
normal saline solution
in weil-felix test, what are the 3 antigen suspension used?
Proteus OX2
Proteus OX19
Proteus OXK
Proteus associated with P. vulgaris
Proteus OX2
Proteus associated with P. mirabilis
Proteus OX19
Proteus associated with Kingsbury strain
Proteus OXK
what is utilized as an antigen in Widal test?
killed salmonella typhi
where does the salmonella typhi grow?
intestines, blood
mode of transmission of typhoid
eating or drinking food or water contaminated with feces of an infected person
what are the dominant antigens that we deal with in widal test?
antigen O, antigen H
somatic antigen
heat stable
antigen O
flagellar antigen
heat labile
antigen H
what is the sample of choice in widal test?
serum
what vacutainers are used for the specimen of widal test?
non-additive vacutainer (red or yellow top)
what drug is taken by the patient while waiting for the result of the Widal test and cultures of blood and stool
chloramphenicol
Vi antigen (capsule/ virulence)
thermolabile, unstable, delicate
K antigen
among all the antigens of S. typhi, what is used for reference laboratories?
K antigen
is the positive result of rapid slide screening method an indication of S. typhi infection?
no
enumerate the degree of agglutination for widal rapid slide titration method
4+ 100% (solid clumps)
3+ 75%
2+ 50%
1+ 25%
Trace less than 25%
Negative no agglutination
(WIDAL’S TEST rapid slide titration) serum volume and approximation tube dilution
0.08ml 1:20
0.04ml 1:40
0.02ml 1:80
0.01ml 1:160
0.005ml 1:320
all positive results obtained through the slide test should be confirmed using the following technique
Widal’s tube agglutination test
incubation time and temperature in water baths for salmonella “O” antigens and proteus
50C for 4 hours
incubation time and temperature in water baths for salmonella “H” antigens and proteus
50C for 2 hours
antibody excess
prozone
antigen excess
postzone which causes negative test result
characterisitc of positive result in widal’s tube agglutination test
obvious floccular agglutination throughout the tube
considered significant titer in the widal’s test
1:80
considered significant titer for weil-felix test
1:160
what causes a stronger agglutination reaction which is not easily dispersed between the types of agglutination test in widal’s
somatic agglutination
fluffy and floccular aggregates that are easily dispersed
flagellar agglutination
significant titer for flagellar agglutination
greater than 80 = indicates infection
indicates acute/recent typhoid fever
INC titer on OD Ag
indicates acute/recent paratyphoid infection
INC titer on OA, OB, OC
indicates previous/ past infection with typhoid fever
convalescent/vaccination against typhoid fever
INC titer on HD Ag
indicates past infection on S. paratyphi
INC titer on HA, HB, HC
indicates mixed infection
INC titer on O and H Ag
what causes typhus fever?
R. prowazekii
what is the mechanism used in weil-felix test
cross reaction mechanism
why does weil-felix test use proteus?
because of the cross-reaction mechanism; rickettsia and proteus possess the same antigenic determinants
