Transcript Typhoid fever

Faculty of Allied Medical
Sciences
Clinical Immunology & Serology
Practice
(MLIS 201)
Typhoid fever
Prof. Dr. Ezzat M Hassan
Prof. of Immunology
Med Res Inst, Alex Univ
E-mail: [email protected]
Teaching Objectives
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To define Typhoid Fever
To know the causes and symptoms of the disease
To understand how the bacteria cause the disease
To know different methods to diagnose Typhoid fever
To define Widal test and its components
To describe the procedure of tube Widal test
To know how to interpret the results
To describe the procedure of slide Widal test
To know the causes of false +ve and flase –ve results
To know the limitations of the test
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Countries endemic for typhoid (U.S. CDC 2006)
Alex LaPointe, Wikimedia Commons
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Definition
• An infectious feverish disease caused by the bacterium Salmonella
typhi and less commonly by Salmonella paratyphi.
• The infection always comes from another human, either an ill person
or a healthy carrier of the bacterium.
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Persons with typhoid fever carry the bacteria in their bloodstream
and intestinal tract
• Transmitted through the ingestion of food or drink contaminated by
the feces or urine of infected people
• The bacterium can withstand both drying and refrigeration.
Causes
1. Caused by the bacterium Salmonella Typhi .
2. Ingestion of contaminated food or water.
3. Contact with an acute case of typhoid fever.
4. Contact with a chronic asymptomatic carrier.
Salmonella typhi
• Rod shaped, flagellated, aerobic, Gram -ve bacilli.
• Refrigeration and freezing could slow their growth.
• Pasteurizing and food irradiation kill Salmonella for
commercially-produced foodstuffs
• Foods prepared in the home from raw eggs can spread
salmonella if not properly cooked before consumption.
How does the bacteria cause disease ?
Ingestion of contaminated food or water
Salmonella typhi
Carried by white blood cells into the liver, spleen, and bone marrow
Multiply and reenter the bloodstream (Clinical illness)
Bacteria invade the gallbladder, biliary system, and the lymphatic tissue of the
bowel and multiply in high numbers
Then pass into the intestinal tract (can be identified for diagnosis in cultures
from the stool)
Typhoid ulcers can cause perforation and hemorrhage
How does the bacteria cause disease ?
Symptoms
• No symptoms - if only a mild exposure; some people
become "carriers" of typhoid.
• Poor appetite, Headaches and generalized pains,
• Fever, Lethargy
• Rose spots on chest wall
• Diarrhea / constipation and abdominal pain
• Chest congestion develops in many patients,
• slow heartbeat.
• Enlarged spleen and liver
Symptoms
Rose spots
Aches and pains
High fever
Diarrhea
Chest congestion
Typhoid Meningitis
Diagnosis
Diagnosis of typhoid fever is made by
• Clinical examination
• Blood, bone marrow, or stool cultures for S. typhi
• Serological Tests
Serodiagnosis of Typhoid :
1.Detection of Antibodies in serum:
1.Widal test (Tube or Slide),
3.Tubex system,
2.Typhidot assay
4. Dipstick assay.
2. Detection of Antigens in serum:
1. Tubex system
2. Countercurrent Immunoelectrophoresis (CIE).
3. Co-agglutination test.
4. ELISA
3. Detection of Antigens in urine:
1.Tubex system
3. Latex agglutination
2. CIE,
4. Co-agglutination
Widal test
• Antigenic structure of Salmonella
H( flagella ) antigens
O (somatic) antigens
Vi (Virulence) capsular
polysaccharide antigens
O (somatic) antigens
H (flagella) antigens
• LPS in the cell wall;
• Heat stable
• Less immunogenic
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• Agglutination with antisera:
Fine, compact, granular
chalky clumps
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Present in flagella;
 Heat labile;
 Strongly immunogenic;
Induce rapid & High Ab titres;
Agglutination with antisera:
Large, loose, cotton wool
clumps
Vi (virulence) antigen
• Capsular polysaccharide expressed on certain serotypes
• Heat labile;
• Poorly immunogenic, BUT antibodies are protective:
1. Detection of Vi antibody not helpful in diagnosis
2. Absence in a case of typhoid  poor prognosis;
3. Persistence of Vi antibody : carrier state
WIDAL Test
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Tube agglutination test.
Detects anti O and H antibodies in serum
Diagnosis of Typhoid and Paratyphoid cases
Carriers of typhoid bacilli possess antibody against
the Vi antigen of S. typhi. (Vi tires seem to correlate
better with the carrier state than do O or H titres).
• For this reason, the use of Vi agglutination for
detection of carriers was suggested .
Dr.T.V.Rao MD
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Widal test
• Significance
 I st week negative.
Titers raise in 2nd week
Raise of titers is diagnostic
Dr.T.V.Rao MD
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Materials
• Antigens:
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Suspension of S. typhi "O" antigen, O
Suspension of S. typhi "H" antigen; H
Suspension of S. paratyphi A "H" antigen, PA
Suspension of S. schottmuelleri "H" antigen, PB
• Antibody: serum of suspected patient
• Normal saline
• Test tubes and pipettes
PROCEDURE
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O
H
PA
PB
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PROCEDURE
• Make the mark of tubes
• Dilute patient’s serum 1:10 (0.1 ml serum + 0.9 ml saline).
• Add reagents as the following:
Reagent (ml)
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2
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Saline
0.5
1:10 Patient serum 0.5
Serum dilution
1:20
Bacteria suspension
0. 5
0. 5
0.5
0. 5
0. 5 0. 5
0.5
0.5
0.5
0.5
0. 5
1:40 1:80 1:160 1:320 1:640
0. 5 0. 5 0. 5
0. 5 0. 5
Final serum dil.
1:80 1:160 1:320 1:640 1:1280
1:40
Bacteria suspension: O H
0. 5
discard
0. 5
-ve
PA PB
Shake several times, put it in 370C water bath for 16-18 hours.
Then let it stand at room temperature over night.
Observation:
**Do not shake tubes before reading the results
1. Control tube (Tube No. 7): no agglutination (-)
2. Lowest titer tube: absolutely agglutination (++++)
3. Other tubes:
¾ agglutination(+++) ½ agglutination (++)
¼ agglutination (+)
no agglutination (-)
Interpretation:
Agglutination titer: the highest dilution of serum
which appears (++) bacteria agglutination.
Agglutination how it appears after
reactivity
O
Felix tube
Round bottom
O agglutination
Compact
granular
agglutination
H
Dreyer’s tube
Conical bottom
H agglutination
Loose
Cotton woolly
clumps
Observed for agglutination:
H : Loose , cotton woolly clumps;
 O : Compact Fine granular agglutination;
Supernatant should be clear;
How do you read Widal test results for
typhoid fever?
• The highest dilution of the patients serum in
which agglutinations occurs is noted, ex. if the
dilution is 1 in 160 then the titer is 160.
• Agglutination in dilution up to <1:60 is seen
in normal individuals . Agglutination in dilution
1:160 is suggestive of Salmonella infection.
• Agglutination in dilution of >1:320 is
confirmatory of Enteric fever .
Interpretation of results
O<1:80, H<1:160, PH<1:80 Normal value
O ≥1:80 & H ≥1:160 or
Typhoid fever
O ≥1:80 & PH ≥1:80
Paratyphoid fever
O ≥1:80 & H <1:160 or
Early infection or other
O ≥1:80 & PH <1:80
salmonella infections
O <1:80 & H ≥1:160 or
Vaccination or nonspecific
O <1:80 & PH ≥ 1:80
memory reaction
Conclusion
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O
++++
++
++
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H
++++
+++
++
++
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PA
++
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PB
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1:40
1:80
1:160 1:320 1:640 :1280
N.B.
Single test not diagnostic (Except at high titers > 320).
Paired samples tests with rising titer is diagnostic
Diagnostic.
O > 1 : 80
H > 1 :160
H agglutinins appear first
Negative
control
Prozone phenomenon in
Agglutination tests
Prozone effect - Occasionally, it is observed that when
the concentration of antibody is high (i.e. lower
dilutions), there is no agglutination and then, as the
sample is diluted, agglutination occurs.
Lack of agglutination in the prozone is due to antibody
excess resulting in very small complexes that do not
clump to form visible agglutination
Limitation of Widal Test
• The Widal test is time consuming and often times
when diagnosis is reached it is too late to start an
antibiotic regimen.
• In spite of several limitation many Physicians
depend on Widal Test
Dr.T.V.Rao MD
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Interpretation of Widal test
• Test results need to be interpreted
carefully in the light of :
1. Past history of enteric fever,
2. Typhoid vaccination,
3. general level of antibodies in the
healthy populations in endemic areas
of the world.
False Positive Reactions with
WIDAL Test
1. patients who have had previous vaccination or
infection with S typhi.
2. Cross-reaction with non – typhoidal Salmonella.
3. in association with some autoimmune diseases.
4. Infection with malaria
False Negative Reactions with WIDAL
Test
1. Early treatment,
2. Relapses of typhoid fever.
3. Occasionally the infecting strains are
poorly immunogenic.
Typical Serological Profile After Acute
Infection
Note that during Reinfections, IgM may be absent or present at a low level transiently
Slide Widal test:
• Slide Widal test is more popular as it gives rapid results.
Qualitative test:
1 drop of undiluted patient’s serum sample for
the 2 antigens is placed on the circled card.
1 drop of each of 2 salmonella antigens are added separately
rotated gently for 1 min.
Appearance of agglutination gives qualitative results.
(semiquantitative test is repeated with dilutions of serum)
Slide Widal test (Cont.):
• Semi-quantitative test:
80µl, 40µl, 20µl, 10µl, 5µl, of patient’s serum each for 2 salmonella antigens are placed
on the circled card.
one drop of specific antigen is added to each series of serum.
Agglutination of each of these is noted.
Interpretation
 80µl corresponds to 1 in 20 dilution.
 40µl corresponds to 1 in 40 dilution.
 20µl corresponds to 1 in 80 dilution.
 10µl corresponds to 1 in 160 dilution.
 5µl corresponds to 1 in 320 dilution.
Prevention
And
Treatment
Prevention
Two main typhoid fever prevention strategies:
1. Vaccination
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2. Avoid risky food and drinks
Medication
Antibiotics
• Antibiotics, such as ampicillin, chloramphenicol, fluoroquinolone
trimethoprim-sulfamethoxazole, Amoxicillin and ciprofloxacin etc used to
treat typhoid fever.
• Prompt treatment of the disease with antibiotics reduces the case-fatality
rate to approximately 1%.
Study Questions:
• Write short note:
Symptoms & Prevention of typhoid fever
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‫‪Assigment‬‬
‫‪• Write shortly on Widal test‬‬
‫ميرنا ابراهيم – نادية محمد سعد – نيهال كمال – هايدى احمد – هدى عبد هللا‬
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THANK YOU
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