Samples
Blood
90% positive in First week
75% Positive in second week
60% positive in third week
25% positive till the fever subsides
Serum
Urine
Stool
Blood culture
5-10 ml of blood taken by venipuncture
Add to blood culture bottle
50-100ml of 0.5% Ox bile broth along with routine blood culture media
Ensure 1:10 dilution
Substances in blood may prevent growth of bacilli
Liqoid ( Sodium Polyanethol Sulphonate) addition will counteract
bactericidal action of blood
Over night incubation @ 37°C
Sub culture on Mac Conkey agar
Non Lactose Fementing colonies
If no growth after 24 hours
Repeat subcultures on alternate days
Negative result can be given only after 10days
Casteneda’s method
Biphasic medium
Bile broth + agar slant
Minimizes contamination
Bottle incubated in upright position
For subcultures bottle needs to be tilted so that broth runs over the
agar surface
Colonies will be formed on slant if blood culture is positive.
Clot culture
Take 5 ml of blood in a sterile test tube
Allow it to clot
Serum taken for widal test
Clot is broken with a sterile glass rod
Broken clot added to bottle of bile broth
Streptokinase is added to broth to help in lysis of clot
Isolation rates are better
Inhibiting action of serum is minimized
Single sample can be used for both culture as well as serology
Feces culture
Bacilli shed throughout disease and convalesence
Positive cultures may be seen in carriers as well
Selective media may be used to increase chances of isolation
Feces culture more useful in patients on antibiotics as salmonellae
manage to survive in the gut excaping antibiotic action
Media used
Mac Conkey
Deoxycholate Citrate Agar
Wilson-Blair
Biochemical reactions
Agglutination testing
Take one drop of saline in 2 slides
Mix loopful of colonies from growth
Look for autoagglutination
To one slide add one drop of “O” antiserum (Group D)
Rock slide gently
Look for agglutination: Positive à Salmonella group D
Repeat the same procedure with H antiserum : Positive à Salmonella typhi
Urine culture
Salmonellae are
shed on & off
Usefulness of
urine culture for diagnosis is questionable
Becomes positive
only by 2nd or 3rd week in 25% cases
Sensitivity may
be enhanced by repeated cultures
Ccmsu --
centrifuged & deposits are inoculated on enrichment & selective media
Other optional
samples
Bone marrow :
may become positive even when blood culture is negative
Bile culture :
obtained by duodenal aspiration
Useful in
detection of carriers as well
Rose spots
Pus from
suppurative lesions
Csf
Sputum
Autopsy
specimens
Gall bladder
Liver
Spleen
Mesentric lymph
nodes
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