Bacteriological diagnosis of enteric fever consists of: Isolation of bacilli Demonstration of...
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Bacteriological diagnosis of enteric
fever consists of:1. Isolation of bacilli2. Demonstration of antibodies3. Demonstration of circulating
antigen4. Other laboratory test
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ISOLATION OF BACILLISpecimens:Blood Urine Faeces Aspirated duodenal
fluid,etc..
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BLOOD CULTUREPositive in,90%-1st week75%-2nd week60% -3rd week25%-till the subsidence of pyrexia
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contd…• Blood collected is cultured on glucose
&taurocholate broth..• We must take care of contamination with
external environment• Dilute or add sodium polyanethol
sulphonate• Incubated at 37degrees• Castaneda’s method is also practiced
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CLOT CULTURE• Aseptically collected blood is
allowed to clot• Serum-used in widal test• Blood clot-added to bile broth
containing streptokinase(causes lysis of blood clot)
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FAECES CULTURE• Salmonella are shed in the faeces
through out the disease even in convalescence
• Antibiotic does not eliminate the bacilli from the GUT as it does 4m BLOOD
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CULTURE• On McConkey agar & DCA media-Pale yellow colonies
• On wilson blair media• S.typhi-black colinies(with metallic sheen)• S.paratyphi-green colonies(due to
absense of hydrogen sulphide• Enrichment media are incubated and
then subcultured on selective media
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On mac conkey agar
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• S.typhi • S.paratyhi
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URINE CULTURE• Not much more imp as blood &
faeces culture• Positive only in 2nd& 3 rd weekes• Urine sample is centrifuged
&inoculated into enrichment &selective media
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Other specimens1. Bone marrow2. Bile 3. Rose spots discharge4. Pus5. Suppurative lesions6. Csf&sputum At autopsy-gallbladder,liver,spleen
& mesenteric lymphnodes
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SLIDE AGGLUTINATION TEST
• A loopful of growth from a nutrient agar is emulsified in two drops of saline on a microscopic slide
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CONTD..• 1st emulsion-control• To show the strain not
agglutable• 2nd emulsion-test• Polyvalent “o”&polyvalent
“H”are added • Positive-presence of
salmonella sps• Then monovalent anti sera
belongs to S.typhi are added• If the isolate is fresh
agglutination is done with “vi”antisera,alternatively the bacterial suspension is boiled for 20 mins which removes the vi antigens
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¤ Non typhoid Salmonella sproducing acid and gas 4m carboydrates is tested for “O” &”H”antisera for groups A,B,C…..
¤ NATIONAL SALMONELLA REFERENCE CENTRE at the CRI
¤ INDIAN VETERINARY RESEARCH INSTITUTE,Izatnagar
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SLIDE AGGLUTINATION
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DEMONSTRATION OF ANTIBODIES
WIDALTEST
PROCEDURE: DREYER”S TUBE - H agglitination FELIXTUBE - O agglutination
28 test tubes are arranged in 4 rows each row containing 7 tubes and named as
1st row-To2nd row-Th3rd row-Ah4th row-Ao
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Contd….• To &Th for the detection of S.typhi• Ao &Ah for the detection of
S.paratyphi• Of the 7 tubes one acts as control
&remaining tubes as test
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Contd…. • A low dilution of patient serum is
1:20 to 1:640• All tubes in rack are incubated at
37 degrees for 24hrs&results are read after over night refrigeration at 4 degrees
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Contd….• Positive H agglutination-formation of
loose,cotton wooly clumps• Positive O agglutination-disc like pattern
at the bottom of tube• In both supernatent fluid is clear• Paratyphoid O antigens are not employed
because theycross react with typhoid O antigen due to their haring of factor 12…
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RESULT
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INTERPRETATION1. Titre depends on stage of disease2. On immunistion with TAB vaccine
individuals may show high titres of antibody
3. In non immunised individuals high titre of H agglutinin indicates entericfever or latent infection
4. ANAMNESTIC REATION:5. In carriers
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DEMONSTRATION OF ANTIGENS
• Ag present in blood and urine• PREPARATION OF ANTIGENS: S.aureus is stabilised with
fprmaldehyde &then coated with S.typhi antibody
• PROCEDURE: Patients serum is mixed with staphylococcal
cells Positive-1st week..• CIEP,ELISA
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OTHER….1. TLC2. DIAZO TEST IN URINE• TLC-leucopenia with a relative
lymphocytosis is found• DIAZO TEST:• Positive -in b/w 5th &14th weeks
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Duration of diseaseS
Specimen examination
%positivity
1st week Blood culture 90%
2nd week Blood culture,Faeces cultureWidal test
75%50%Low titre
3rd week Widal testBlood cultureFaeces culture
80-100%60%80%
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CARRIERS
Convalescent carriers Healthy carriers Chronic
carriers
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DIAGNOSIS…..• SPECIMENS:stool,urine,bile,duodenal drainage Antibody ti vi antigen in serum is clamied
indicate thecarrier stateConvalescent &healthy carriers shed bacilli in
faeces from 2 months to 1 yr…Where as chronic carriers shed bacilli in faeces
from 1yr to several years
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• BACTERIOPHAGE TYPING:• BIO TYPING• PLASMID TYPING
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• ANTOIBIOTICS:• chloramphenicol• ampicillin• furazolidone• cotrimoxazole• For multiresistent cases:• flouroquinolones• 3rd generation cephalosporins• Resistence has been devoloped to antibiotics• In salmonella gastro enterits antibiotics should
not be used
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1. Maintaining highgenic conditions2. Carriers should not be engaged in
food preparation3. Vaccination
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TAB vaccine• Heat killed,whole celled,• S.typhi-1,000 millions/ml• S.paratyphi A-750 millions/ml• S.paratyphi B-750 millions/ml• Dose schedule:• Protection:• Side effects:
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TYPHOID VACCINE• Live oral,• Avirulent mutent strain• S.typhi lacking UDP-galactose-4-
epimerase has been used`as live oral vaccine
• Dose schedule:• Protection:
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TYPHIM-Vi• Purified Vi antigen• Dose schedule :im • singledose• 25 micro grams
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