DIAGNOSIS OF TYPHOID FEVER updated

Dr.T.V.Rao MD

Dr.T.V.Rao MD 1

Typhoid fevercommon problem in developing

Countries

Manifest with

Rose spots

High fever

Diarrhea

Typhoid Meningitis

Aches and pains

Chest congestion

Clinical manifestation• Head ache, malise,anorexia ,coated tongue • Abdominal discomfort,• Constipation / Diarrhea • Step ladder type fever,• Relative bradycardia,• A soft palpable spleen• Hepatomegaly• Rose spots appear

Dr.T.V.Rao MD 4

Over view of Diagnosis of Typhoid Fever

• Infection with typhoid or paratyphoid fever results in a very low-grade septicaemia. A single blood culture is positive in only half of cases. Stool culture is not usually positive during the early phase of the disease. Bone marrow culture increases the diagnostic yield to about 80% of cases.

Dr.T.V.Rao MD 5

Bacteriological Diagnosis of Typhoid Fever

• Selective media, such as Deoxycholate-citrate agar or xylose-lysine Deoxycholate agar, are used for the isolation of salmonella bacteria from faeces. Fluid enrichment media, such as Tetrathionate or selenite broth, are also useful to detect small numbers of salmonellae in faeces, foods or environmental samples.

Dr.T.V.Rao MD 6

Bacteriological Diagnosis of Typhoid Fever

• Suspicious colonies from the culture plates are tested directly for the presence of Salmonella somatic (O) antigens by slide agglutination and subcultured to peptone water for the determination of flagellar (H) antigen structure and further biochemical analysis.

Dr.T.V.Rao MD 7

Bacteriological Diagnosis of Typhoid Fever

• A presumptive diagnosis of salmonellosis can often be made within 24 h of the receipt of a specimen, although confirmation may take another day, and formal identification of the serotype takes several more days. A negative report must await the result of enrichment cultures - at least 48 h.

Dr.T.V.Rao MD 8

How we Diagnose Typhoid Fever• Diagnosis is made by any blood, bone marrow or

stool cultures and with the Widal test (demonstration of salmonella antibodies against antigens O-somatic and H-flagellar ). In epidemics and less wealthy countries, after excluding malaria, dysentery or pneumonia, a therapeutic trial time with chloramphenicol is generally undertaken while awaiting the results of Widal test and cultures of the blood and stool.

Dr.T.V.Rao MD 9

Laboratory Diagnosis ofTyphoid Fever

• 1 Isolation of Bacilli. A Gold standard • 2 Diagnosis for presence of Antibodies,• Positive Blood culture – A gold standard• Isolation from Feces and Urine ?• Detection of Antibodies Inconclusive.• Newer methods Detection of antigen in Blood and Urine

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Blood Culture1 st week Positive in 90 %2 nd week Positive in 75 %3 rd week Positive in 60 %> 3 weeks positive in 25 %Draw 5 – 10 cc of Blood by venipuncture. ADD to 50 -100 ml of Bile broth.Incubate at 37 c /Subculture in MacConkey At regular intervals

Dr.T.V.Rao MD 11

Blood Cultures in Typhoid Fevers• Bacteremia occurs early

in the disease • Blood Cultures are

positive in 1st week in 90%2nd week in 75%3rd week in 60%4th week and later in 25%

Dr.T.V.Rao MD 12

Castaneda’s method ofBlood Culture

• Double medium used Solid/Liquid medium in the same Bottle.

• Bottle contains Bile broth/agar slant,• For subculture the bottle is merely tilted.• A subculture into MacConkey at regular

intervals,• Reduces the chances of contamination• Increases the chances of isolation.

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Salmonella on Mac Conkey's agar

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Salmonella on XLD agar

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Clot culture• Clot cultures are more

productive in yielding better results in isolation.

• A blood after clotting, the clot is lysed with Streptokinase ,but expensive to perform in developing countries.

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Bactec and Radiometric based methods are in recent use

• Bactek methods in isolation of Salmonella is a rapid and sensitive method in early diagnosis of Enteric fever.

• Many Microbiology Diagnostic Laboratories are upgrading to Bactek methods

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Biochemical Characters

• Non Lactose fermenter,• Motile• Indole – MR + VP - Citrate +• Ferment Glu/Mal/Man• Do not ferment Lactose/Sucrose

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Slide agglutination tests• In slide agglutination

tests a known serum and unknown culture isolate is mixed, clumping occurs within few minutes

• Commercial sera are available for detection of A, B,C1,C2,D, and E.

Dr.T.V.Rao MD 19

Culturing other Specimens

• Feces Enrichment in Tetrathionate broth and Selenite broth

• Culturing in MacConkey/DCA/Wilson Blair medium – Large black colonies.

• Urine Culture – positive in 25 % • Other samples Bone Marrow,Bile,CSF/Sputum

Dr.T.V.Rao MD 20

Why we still use Widal test • The Widal test is an

old serologic assay for detecting IgM and IgG to the O and H antigens of salmonella. The test is unreliable but is widely used in most developing countries because of its low cost. Dr.T.V.Rao MD 21

Serology• WIDAL Test – Tube agglutination test.• Detects O and H antibodies• Diagnosis of Typhoid and Paratyphoid• Testing for H agglutinins in Dryers tubes, a

narrow tube floccules at the bottom• Testing for O agglutinins in Felix tubes, Chalky • Incubated at 37º c overnight

Dr.T.V.Rao MD 22

Widal Test• In 1896 Widal A professor of

pathology and internal medicine at the University of Paris (1911–29), he developed a procedure for diagnosing typhoid fever based on the fact that antibodies in the blood of an infected individual cause the bacteria to bind together into clumps (the Widal reaction).

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Widal test• S.typhi O and H tubes• Paratyphi A/B H agglutinins only• Common antigens O in all Factor sharing

12• Significance • I st week negative.• Titers raise in 2nd week Raise of titers

diagnosticDr.T.V.Rao MD 24

Diagnosis of Enteric FeverWidal test

• Serum agglutinins raise abruptly during the 2nd or 3rd week

• The Widal test detects antibodies against O and H antigens

• Two serum specimens obtained at intervals of 7 – 10 days to read the raise of antibodies.

• Serial dilutions on unknown sera are tested against the antigens for respective Salmonella

• False positives and False negative limits the utility of the test

• The interpretative criteria when single serum specimens are tested vary

• Cross reactions limits the specificity

Widal Test• Single test not diagnostic.• Paired samples tests• Diagnostic. O > 1 in 80 H > 1in 160H agglutinins appear firstFalse positives in Unapparent infection, Immunization Previously infected

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Widal test• Anamnestic response previous

infection and responding to unrelated infection

• Other Diagnostic tests CIE and ELISADetection of Circulating antigensCo agglutination test.

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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

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False Positive and Negative Reactions with WIDAL Test

• The Widal test should be interpreted in the light of baseline titers in a healthy local population. This is especially important when there is a high local prevalence of non-typhoid salmonellosis. The Widal test may be falsely positive in patients who have had previous vaccination or infection with S typhi.

Dr.T.V.Rao MD 29

False Positive and Negative Reactions with WIDAL Test

• Widal titers have also been reported in association with the dysgammaglobulinaemia of chronic active hepatitis and other autoimmune diseases.64 '8 '9 False negative results may be associated with early treatment, with "hidden organisms" in bone and joints, and with relapses of typhoid fever. Occasionally the infecting strains are poorly immunogenic.

Dr.T.V.Rao MD 30

Diagnosis of Carriers and Environments

• Fecal carriers by isolation from specimens. or Bile aspirated.

• Sewer swabs• Bacteriophage

typing

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Culturing and Identifying remain the Gold standard

• Newer serologic assays for S. enterica serotype Typhi infection are occasionally used in outbreak situations and are somewhat more sensitive and specific than the Widal test, but are not an adequate substitute for blood, stool, or bone marrow culture.

Dr.T.V.Rao MD 32

Is there a definitive test to diagnose Typhoid fever

• Because there is no definitive serologic test for typhoid or paratyphoid fever, the initial diagnosis often has to be made clinically. The combination of a history of risk for infection and a gradual onset of fever that increases in severity over several days should raise suspicion of typhoid or paratyphoid fever.

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Newer methods in diagnosis of Typhoid Fever

• The serum samples can be tested by using newer methods Multi-Test Dip-S-Ticks, TyphiDot, and TUBEX to detect immunoglobulin G (IgG), IgG and IgM, and IgM, respectively. Dr.T.V.Rao MD 34

Immunoassays in Typhoid Fever

• The immunoassay is also used for the diagnosis. The immunoassay are based on the detection of the O and Vi antigens of S. typhi in blood or urine using conglutination, ELISA, or counter current immunoelectrophoresis. Dr.T.V.Rao MD 35

Experimental and Molecular Methods

• Polymerase chain reaction and DNA probe method attempt to employ S.typhi genes and hybridize them with labelled specific gene probes were also used.

Dr.T.V.Rao MD 36

Key points• Antibiotics have no place in the

management of salmonella gastroenteritis unless invasive complications are suspected.

• Clean water, sanitation and hygienic handling of foodstuffs are the keys to prevention.

Dr.T.V.Rao MD 37

Coalition against Typhoid• Since May 2011, the

Coalition against Typhoid (CaT) has featured monthly articles in the WHO’s Global Immunization Newsletters (GIN). The articles, written by CaT members from around the world, highlight important work being done to accelerate adoption of typhoid vaccines.

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• Programme Created by Dr.T.V.Rao MD for Medical and Paramedical students in

the Developing world• Email

• doctortvrao@gmail.com

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