ReadyPlate™55 CCA ISO9308 Ecoli and Coloriform Bacteria

Description

Mode of Action
The interaction of selected peptones, pyruvate, sorbitol and phosphate buffer promotes rapid colony
growth, even for sub-lethally injured coliform bacteria. The growth of Gram-positive bacteria as well as
certain Gram-negative bacteria is inhibited by the presence of Tergitol®7 which has no negative effect
on the growth of coliform bacteria.
Further, the combination of two chromogenic substrates permits the simultaneous detection of coliform
bacteria and E. coli.

Coliform bacteria detection: The substrate Salmon-GAL is used for the detection of β-D-galactosidase
activity, which is characteristic for coliform bacteria. This interaction results in a pink to red color of the
coliform colonies.

E. coli detection: The substrate X-glucuronide is used for the detection of β-D-glucuronidase activity,
which is characteristic for E. coli.
E. coli cleaves both Salmon-GAL and X-glucuronide, so that positive colonies take on a dark-blue to violet
color. These are easily distinguished from other coliform colonies, which have a pink to red color.
Some E. coli (3-4%) are β-D-glucuronidase-negative and appear as pink to red colonies, e.g. most E.
coli O157 strains. For the detection of E. coli O157 specific culture media should be used.
Accompanying flora appears as colorless colonies, except for some organisms, which possess β-Dglucuronidase activity. These colonies appear light blue to turquoise in color.

Typical Composition
ReadyPlate™ 55 Chromocult®
Enzymatic Digest of Casein 1 g/l
Yeast Extract 2 g/l
NaCl 5 g/l
NaH2PO4 x 2 H2O 2.2 g/l
Na2HPO4 2.7 g/l
Sodium Pyruvate 1 g/l
Sorbitol 1 g/l
Tryptophane 1 g/l
Tergitol® 7 0.15 g/l
6-Chloro-3-indoxyl-beta-Dgalactopyranoside 0.2 g/l
5-Bromo-4-chloro-3-
indoxyl-D-glucuronic acid 0.1 g/l
Isopropyl-beta-Dthiogalactopyranoside 0.1 g/l
g/l Agar-agar* 10 g/l
Water 1000 ml Water 1000 ml/l
* Agar-agar is equivalent to other different terms of agar.

The appearance of the medium is opalescent to turbid and yellowish. The pH value at 25 °C is in the
range of 6.6-7.0.
Protect plates from prolonged exposure to light during preparation and application, as this may affect
the coloration of the colonies

Application and Interpretation
Please check each agar plate before using it on sterility and pay attention to aseptic handling in order to
avoid false positive results.
Prepare test samples using standard laboratory techniques such as those described in the applicable ISO
standard, Bacteriological Analytical Manual, or Standard Methods for the Examination of Water and
Wastewater specific for the product concerned.
Drinking water and waters with low bacterial background: Chromocult® Coliform Agar acc. ISO
9308-1 is usually combined with membrane filtration for water analysis.