Chromocult Enterococci Agar

Enterococci Agar, Chromocult^®

Cat. No. 1.00950.0500
(500 g)

Selective culture medium for the isolation, differentiation, and enumeration of Enterococci in water, foodstuffs, and other materials.

Mode of Action	Typical Composition
Preparation	Quality Control
Experimental Procedure and Evaluation	Literature

Mode of Action
The presence of Enterococci, especially E. faecalis, E. faecium, E. durans, and E. hirae, serves as an indicator for fecal contamination.

Growth of Enterococci is stimulated by selected peptones, phosphates, and addition of Tween^® 80. Enterococci cleave the unique chromogenic substrates in the medium. This produces red colonies allowing an easy detection of Enterococci.

Sodium azide and ox bile inhibit most accompanying microbial flora. Non-Enterococci produce colorless, blue/violet, or turquoise colonies. These colonies are easily distinguished from the red colored Enterococci colonies.

Typical Composition (g/liter)
Peptones 10.0; sodium chloride 5.0; sodium azide 0.2; di-potassium hydrogen phosphate 3.4; potassium di-hydrogen phosphate 1.6; ox bile 0.5; Tween^® 80 1.0; chromogenic-mixture 0.25; agar-agar 11.0.

Preparation

Suspend 33.0 g in 1 liter of purified water by heating in a boiling water bath or in a flowing steam. Stir the contents to assist dissolution (approximately 45 minutes), let the medium cool to 45-50°C and pour into plates.

DO NOT AUTOCLAVE! DO NOT OVERHEAT!

pH: 7.0 ± 0.2 at 25°C.

The plates are clear and slightly yellow. If stored at +4 ±2°C and protected from light, the plates are stable for 2 weeks.

Experimental Procedure and Evaluation
Inoculate the medium by the pour-plate method or by spreading the sample material on the surface of the plates. In addition, the membrane-filter technique may also be used.

The type of membrane filter affects the performance of the medium (growth and coloration of colonies). Best results were obtained using membrane filters of cellulose-mixed-ester material, e.g. Gelman GN-6 (OSSMER, 1999).

Incubation: 24 ± 4 hours at 35-37°C.
If there is no color change or any visible growth after 24 ±4 hours, continue the incubation up to 44 ± 4 hours.

Enterococci:
Red colonies with a diameter of 0.5 to 2mm.

Non-Enterococci:
Colorless (e.g. Aerococcus viridans ATCC 29503), blue/violet (e.g. Aerococcus viridans ATC 10400), turquoise (e.g. Streptococcus equi ATCC 33398).

Quality control

Test strains	Inoculum (cfu/plate)	Growth	Colony Color
Enterococcus faecalis ATCC 19433	30 - 300	Good	Red
Enterococcus faecium ATCC 882	30 - 300	Good	Red
Enterococcus durans ATCC 6056	30 - 300	Good	Red
Enterococcus hirae ATCC 8043	30 - 300	Good	Red
Aerococcus viridans ATCC 10400	1000 - 2000	Fair/None	Blue/Violet
Bacillus cereus ATCC 11778	1000 - 2000	--	--
Escherichia coli ATCC 11775	1000 - 2000	--	--
Pseudomonas aeruginosa ATCC 27853	1000 - 2000	--	--

Literature

H., W. DOTT, G. HAVEMEISTER, H.E. M�LLER and C. SACR�. 1982. Faecal streptococci as indicator organisms of drinking water. Zbl.Bakt.Hyg.,I.Abt.Orig.A 252:154-165
OSSMER,R. ; SCHMIDT,W.; MENDE,U.; 1999. Chromocult Coliform Agar - Influence of Membrane Filter Quality on Performance . Posterpresenation Congresso de la Sociedad , Espanola de Microbiologia , Granada , Spain.
AMOROS, I. 1995. Evaluation of Chromocult Enterococci Broth (with Agar). Posterpr�sentation Congress of Spanish Society of Microbiology, Madrid.
LITSKY, W., W.L. MALLMANN and C.W. FIFIELD. 1953. A new medium for the detection of enterococci in water. Amer.J.Pbl.Hlth. 43:873-879
MANAFI, M. and K. WINDHAGER. 1997. Rapid identification of enterococci in water with a new chromogenic assay. Abstr. P-107, pp.453, Abstracts of the 97th Meeting of the American Society for Microbiology, Miami, USA.
SNYDER, M.L. and H.C. LICHSTEIN. 1940. Sodium azide as an inhibiting substance for gram-negative bacteria. J.Infect.Dis. 67:113-115
MANAFI, M. and K. LANG. 2004. Isolation and identification of Enterococci from food on a novel chromogenic medium. Poster presentation, The 19th International ICFMH Symposium, Food Micro 2004, 12 - 16 September, 2004, Slovenia.