This is a differential medium for the detection of
salmonellae and other enteric pathogens, by means o
f lactose fermentation, lysine
decarboxylase activity and hydrogen sulphide produc
) which ferment lactose and
produce black colonies on Bismuth Sulphite Agar (LA
B13) can be recognised by the alkaline reaction (pu
rple colour) produced throughout
the medium, together with blackening due to sulphid
e production. Enteric organisms that do not decarbo
xylate lysine yield an alkaline slant
over an acid butt (yellow). Thus no distinction bet
is possible and Triple Sugar Iron Agar (LAB53) is
recommended in parallel.
cultures characteristically produce a distinctive r
ed slant over an acid butt since these
organisms deaminate lysine but without sulphide pro
strains which produce pink to red colonies on bile
media are often overlooked in outbreaks of food poi
soning, however the use of Bismuth Sulphite Agar wi
th subculture into Lysine Iron Agar
allows determination of their presence.
Method for reconstitution
Weigh 31.5 grams of powder and disperse in 1 litre
of deionised water. Allow the mixture to soak for 1
0 minutes, swirl to mix and bring to
the boil, with frequent stirring to dissolve comple
tely. Dispense into tubes and sterilise by autoclav
ing at 121°C for 15 minutes. Cool in a
slanted position such that slopes are formed over d
eep butts approx. 3cm in depth.
Clear purple gel.
6.7 ± 0.2
Storage of Prepared Medium:
Tightly capped containers – up to 3 months at 15-20
°C in the dark.
Subcultures for further identification are picked f
rom the centre of isolated colonies on selective me
dia and streaked across
the slant and stabbed into the butt of tubes of Lys
ine Iron Agar.
37°C aerobically for 18-24 hours.
Edwards, P.R. and Fife, M.A. (1961). Lysine iron ag
ar in the detection of Arizona cultures. Appl. Micr
Edwards, P.R. and Ewing, W.H. (1964). Identificatio
n of Enterobacteriaceae. Burgess Publishing Co. Min