Salmonella spp.

Salmonella spp. (Gram Negative)

Enriched sample in Lactose broth, incubate 35˚C 24Hrs
Draw 1 ml of Broth to Selenite Cysteine (SC)Broth, incubate 35˚C 24Hrs
Draw 1 ml of Broth to Tetrathionate (TT) Broth, incubate 35˚C 24Hrs
Prepare BS , HE, XLD agar plates
Divide the perti dishs into half, 1 for SC and 1 for TT
2 phase streak SC and TC to all the plates with the designated halfs
Incubate 35˚C for 24hrs
From each media and section, pick 1 positive colony
Inoculate into TSI and LIA broth

Other method available is ELISA

BS (Inhibit against Coliform and Gram positives) positive will yield Black-Green colony with metallic sheen
HE agar (select against gram positives) positive will be blue colony with black centre
XLD ( Select for Salmonellae) agar positive colony will be red with black centers.
TSI Positive Red slant, yellow butt with black ppt.
LIA positive , purple slant, purple butt with black ppt.

Bismuth Sulfiteagar (BS)
Contains sulfite which will differentiate desulphydrase producer, which will yield a black ppt (H2S).
Bismuth suppresses gram Coliform
Brilliant green suppresses G+


Hektoen Enteric Agar
Bile salts, bromothymol blue, acid fuchsin suppresses G+ bacteria
bromothymol blue, acid fuchsin acts as indicator, salmonella consumes peptone which will give off alkaline pdt. pH Indicator will turn green .
Thiosulphate provides an indicator for activity of desulphydrase (salmonella), which will yield H2S ( Black ppt.)

Lysin Iron Agar (LIA)
Contains Lysine, Fe , Glucose, thiosulphate,bromocresol purple indicator
After depletion of glucose, it will utilise(‘ve lysine decarboxlyase) lysine and produce base pdt, which will cause indicator to turn purple ( purple butt)
Desulphydrase will give out H2S, which combines with Fe to give a black ppt.

Triple Sugar Iron agar ( TSI)
Contains glucose, sucrose, lactose, Fe, and thiosulphate, indicator phenol red
Salmonella ferments either or all the sugars to produce acid at the butt , i.e. yellow.
Desulphydrase will give out H2S, which combines with Fe to give a black ppt
Xylose Lysine Desoxycholate Agar (XLD)Desoxycholate inhibits non-members of Enterobacteriaceae. Thiosulphate and Fe has same fuction as the above media. Salmonella ferments xylose, therefore favours xylose fermentors. Lysine will differentiate xylose and non xylose fermentor(similar function as (LIA), phenol red indictor will turn red when pH is basic.