Bacteriological diagnosis of enteric fever consists of:
1. Isolation of bacilli
2. Demonstration of antibodies
3. Demonstration of circulating antigen
4. Other laboratory test

Specimens:Blood
Urine
Faeces
Aspirated duodenal fluid,etc..

Positive in,
90%-1 st week
75%-2 nd week
60% -3 rd week
25%-till the subsidence of pyrexia

• 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

• 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)

• 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

• On McConkey agar & DCA mediaPale 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

• S.typhi
• S.paratyhi

• Not much more imp as blood & faeces culture
• Positive only in 2 nd & 3 rd weekes
• Urine sample is centrifuged
&inoculated into enrichment
&selective media

1. Bone marrow
2. Bile
3. Rose spots discharge
4. Pus
5. Suppurative lesions
6. Csf&sputum
At autopsy-gallbladder,liver,spleen
& mesenteric lymphnodes

SLIDE AGGLUTINATION TEST
ful of growth from a nutrient
is
microscopic slide

• 1 st emulsion-control
• To show the strain not agglutable
• 2 nd 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

¤ 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

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
1 st row-To
2 nd row-Th
3 rd row-Ah
4 th row-Ao

• 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

• 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

• 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…

1. Titre depends on stage of disease
2. 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

• 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-1 st week..
• CIEP,ELISA

1. TLC
2. DIAZO TEST IN URINE
• TLC-leucopenia with a relative lymphocytosis is found
• DIAZO TEST:
• Positive -in b/w 5 th &14 th weeks

Duration of diseaseS
1 st week
Specimen examination
%positivity
Blood culture 90%
2 nd week
3 rd week
Blood culture,
Faeces culture
Widal test
75%
50%
Low titre
Widal test
Blood culture
Faeces culture
80-100%
60%
80%

CARRIERS
Convalescent carriers
Healthy carriers
Chronic carriers

• SPECIMENS: stool,urine,bile,duodenal drainage
Antibody ti vi antigen in serum is clamied indicate thecarrier state
Convalescent &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

• BACTERIOPHAGE TYPING:
• BIO TYPING
• PLASMID TYPING

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•
•
•
• ANTOIBIOTICS: chloramphenicol ampicillin furazolidone cotrimoxazole
• For multiresistent cases:
•
•
• Resistence has been devoloped to antibiotics
• In salmonella gastro enterits antibiotics should not be used flouroquinolones
3 rd generation cephalosporins

1. Maintaining highgenic conditions
2. Carriers should not be engaged in food preparation
3. Vaccination

• 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:

• Live oral,
• Avirulent mutent strain
• S.typhi lacking UDP-galactose-4epimerase has been used`as live oral vaccine
• Dose schedule:
• Protection:

•
•
• Purified Vi antigen
• Dose schedule :im singledose
25 micro grams