ENDO Agar

ENDO Agar

EMD Cat. No. 1.04044.0500/5000

500 g, 5 kg

Selective culture medium for the detection and isolation of E. coli and coliform bacteria in various materials according to ENDO (1904)

This medium complies with the "Standard Methods for the Examination of Water and Wastewater" (1992).

Mode of Action	Preparation
Experimental Procedure and Evaluation	Quality Control
Typical Composition (g/liter)	Literature
Picture/Image

Mode of Action
Sodium sulfite and fuchsin inhibit the growth of gram-positive bacteria. E. Coli and coliform bacteria metabolize lactose with the production of aldehyde and acid. The aldehyde liberates fuchsin from the fuchsin-sulfite compound, the fuchsin then colors the colonies red. In the case of E. coli, this reaction is so intense that the fuchsin crystallizes out giving the colonies a permanent greenish metallic sheen (fuchsin sheen). Lactose-negative and wealkly lactose-positive E. coli do not show any fuchsin sheen.

Typical Composition (g/liter)
Peptones 10.0; di-potassium hydrogen phosphate 2.5; lactose 10.0; sodium sulfite, anhydrous 3.3; pararosanilin (fuchsin) 0.3; agar-agar 12.5.

Preparation
Suspend 39 g in 1 liter of purified water. Autoclave (15 min at 121°C). Pour plates.
The plates are clear and pale pink.
If the culture medium is somewhat too red after it has solidified, the red coloration can be removed by adding a few drops (max. 1 ml/liter) of a freshly prepared 10 % sodium sulfite solution and then boiling.
pH: 7.4 ± 0.2 at 25°C.

On exposure to oxygen the plated culture medium gradually becomes red due to the oxidation of sulfite and can thus no longer be used. It can only be kept for a few days even if it is stored in the dark and at refrigerator temperature.

Experimental Procedure and Evaluation
Inoculate the plates by the streak-plate method.
Incubation: 24 hours at 35°C aerobically.

Appearance of Colonies	Microorganisms
Red	Lactose-positive:
Red with a permanent metallic sheen	Escherichia coli
Red to reddish, hemispherical, mucoid	Enterobacter aerogenes, Klebsiella and others
colorless, clear	Lactose-negative

Quality control

Test strains	Growth	color change to red	Metallic sheen
Escherichia coli ATCC 25922	good / very good	+	+
Escherichia coli 194	good / very good	+	+
Escherichia coli ATCC 11775	good / very good	+	+
Enterobacter cloacae ATCC 13047	good / very good	+ (poor)	±
Klebsiella pneumoniae ATCC 13883	good / very good	+	none / poor
Salmonella typhimurium ATCC 14028	good / very good	-	-
Shigella flexneri ATCC 12022	good / very good	-	-
Proteus mirabilis ATCC 14153	good / very good	-	-
Enterococcus faecalis ATCC 11700	none / fair	-	-

Additives

EMD Cat. No.	Product	Pack Size
B10357-34	Sodium sulfite	500 g

Literature

American Public Health Association, American Water Works Association and Water Pollution Control Federation: Standard Methods for the Examination of Water and Wastewater, 20th ed., Washington, 1998.
ENDO, S.: Über ein Verfahren zum Nachweis von Typhusbacillen. - Centralbl. Bakt. I. Orig., 35; 109-110 (1904).

E.coli, Salmonella typhimurium