Part of Thermo Fisher Scientific
Organisms this product works with:
Other products used in the isolation of Enterococcus :
KF STREPTOCOCCUS AGAR BASE
Code: CM0701
a selective medium for the isolation and enumeration of enterococci
Typical Formula* | gm/litre |
Proteose peptone | 10.0 |
Yeast extract | 10.0 |
Sodium chloride | 5.0 |
Sodium glycerophosphate | 10.0 |
Maltose | 20.0 |
Lactose | 1.0 |
Sodium azide | 0.4 |
Bromo-cresol purple | 0.015 |
Agar | 20.0 |
pH 7.2 ± 0.2 @ 25°C |
TTC SOLUTION (1%)
Code: SR0229
Vial contents (each vial is sufficient for 500ml of medium) | |
2,3,5-Triphenyltetrazolium chloride (1%) | 5ml |
Directions
Suspend 38.2g in 500ml of distilled water. Bring to the boil with frequent agitation. Boil for 5 minutes. Cool to 50°C and add aseptically 1 vial (5ml) of 1% 2,3,5-Triphenyltetrazolium chloride (SR0229K). Pour into sterile Petri dishes when using the membrane filtration method or hold at 45°C when using the pour-plate method.
Description
KF Streptococcus Agar is based on the formulation described by Kenner et al.1 and is recommended2 for the detection and enumeration of enterococci in faeces, milk, water and other materials by the pour-plate or membrane filtration method. The presence of enterococci in the material under test is indicative of faecal pollution by man or animals.
KF Streptococcus Agar Medium is selective for the following Group D and Group Q species.
Enterococcus group
Enterococcus faecalis | Group D |
Enterococcus subsp. liquefaciens | Group D |
Enterococcus faecalis subsp. zymogenes | Group D |
Enterococcus faecium | Group D |
Enterococcus bovis | Group D |
Enterococcus equinus | Group D |
Streptococcus avium | Group Q |
Streptococcus avium (Group Q) has been included in the `enterococci’ group as it has very similar biochemical and antigenic characteristics to the Group D species and also occurs in warm-blooded animals.
The detection of enterococci may provide more specific information about the source of pollution because certain enterococci are host specific. For example, a predominance of Enterococcus bovis and Enterococcus equinus would indicate pollution due to animal excrement.
The detection of Enterococcus bovis and Enterococcus equinus species has been found to be associated with pollution involving meat processing plants, dairy wastes and feedlot and farmland run-off.
The detection of these enterococcal species is indicative of recent contamination as the organisms survive for only a short period outside their natural habitat. The coliform/enterococci ratios may also provide information on possible sources of pollution2.
Caution must be observed when assessing the quality of marine recreational waters, particularly in tropical climates, because a high incidence of false-positive presumptive counts for enterococci may occur. Anaerobic incubation of tropical marine water samples is recommended3.
Colonies of enterococci on the membrane filter or agar plate are red or pink with a variation in diameter from 0.3 to 2mm. It is recommended that counting should be done with the aid of a low power (10-15 magnification) binocular wide field dissecting microscope or equivalent optical device.
Technique
Membrane Filtration Technique
Plate Count Method
Storage conditions and Shelf life
Store the dehydrated medium at 10-30°C and use before the expiry date on the label.
Store the prepared plates at 2-8°C.
Appearance
Dehydrated medium: Straw coloured, free-flowing powder
Prepared medium: Purple coloured gel
Quality control
Positive control: | Expected results |
Enterococcus faecalis ATCC® 29212 * | Good growth; red coloured colonies with yellow halos |
Negative control: | |
Escherichia coli ATCC® 25922 * | Inhibited |
Precautions
Observe the HAZARD precautions regarding sodium azide when disposing of the medium. The pH of the medium should not fall below 7.0 as it may become inhibitory towards enterococci1. KF Streptococcus Agar is not specific for the presumptive identification of Group D streptococci. Further tests must be made to confirm the identity of the organisms isolated.
References
1. Kennor G.A., Clark H.F. and Kabler P.W. (1961) J. Appl. Microbiol. 9. 15-20.
2. American Public Health Association (1981) Standard Methods for the Examination of Water and Wastewater, 15th Edn. APHA Inc. Washington DC.
3. Fujioka R.S., Ueno A.A. and Narikawa O.T. (1984). Technical Report number 168, Water Resources Research Center, University of Hawaii at Manoa, Honolulu.