Lactose-negative colonies
Istrati-Meitert Agar
READING
Lactose-positive bacteria (Escherichia coli) form yellow, opaque colonies.
Lactose-negative bacteria form transparent, blue-green colonies (Salmonella,
Shigella), sometimes with black center (Proteus).

BILE PREPARATION - harvest ox bile, wait 24 hours for sedimentation. Distribute
the upper phase in trays and dry at 60 ºC.  Triturate in a mortar the dryed product. A
8-10% solution obtained from dry bile is equivalent with fresh bile.

REFERENCES
1. H. Raducanescu, V. Bica-Popii,1986. Bacteriologie veterinara, Ed. Ceres,
Bucuresti.
2. Alexandru Rafila: Medii de cultura, medii de transport si conservare. In Dumitru
Buiuc, Marian Negut: Tratat de microbiologie clinica ed. III, 2009, 1045-1084.
COMPOSITION
Lactose .......................................................................................... 1.5 g
Dry ox bile....................................................................................... 0.8 g
Sodium citrate .............................................................................. 0.8 g
Na hiposulfite ............................................................................... 0.8 g
Fe citrate ........................................................................................ 0.2 g
Bromthymole blue 0.2% solution ........................................... 4.0 ml
Agar .............................................................................................. 12.0 g
Distilled water ad 1000ml.
Distribute in Petri dishes.
DESCRIPTION
Selective - differential medium for Enterobacteriaceae isolation. Favorize Gram-negative bacteria and inhibits Gram - positives.
Inhibits the swarming of Proteus.
Istrati - Meitert agar
Istrati-Meitert agar
(c) Costin Stoica
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