Deskripsi

Himedia M127-500G EC Broth

Himedia M127-500G EC Broth

EC Broth M127
Intended Use:
Recommended for the selective enumeration of presumptive Escherichia coli by MPN technique from water samples
and from clinical samples.
Composition**
Ingredients Gms / Litre
Tryptone 20.000
Lactose 5.000
Bile salts mixture 1.500
Dipotassium hydrogen phosphate 4.000
Potassium dihydrogen phosphate 1.500
Sodium chloride 5.000
Final pH ( at 25°C) 6.9±0.2
**Formula adjusted, standardized to suit performance parameters

Directions

Suspend 37.0 grams in 1000 ml purified/distilled water. Heat if necessary to dissolve the medium completely. Dispense
in test tubes containing inverted Durhams tube. Sterilize by autoclaving at 15 lbs pressure (121°C) for 15 minutes. Adjust the
concentration of medium in accordance with sample size.

Principle And Interpretation

EC Medium is used for detection of coliforms during bacteriological examination of water, milk and foods. It was
originally described by Hajna and Perry (3). This medium was later used by Fishbein and Surkiewicz to carry out
Escherichia coli confirmatory tests (2). It is also used in MPN methods (1) and is often used for confirmation of
coliforms. The procedure employing EC Medium provides information regarding the source of the coliform group (fecal
or non-fecal) when used as a confirmatory test (6). EC Broth should not be used for the ddirect isolation of
coliforms since prior enrichment in a presumptive medium for optimal recovery of faecal coliforms is required.

Tryptone provides nitrogenous and carbonaceous compounds, long chain amino acids and other essential growth
nutrients. Lactose is the fermentable sugar. Bile salts mixture inhibit gram-positive bacteria especially bacilli
and faecal Streptococci. Phosphates control the pH during fermentation of lactose. Gas production in a fermentation
tube within 24 hour or less is a presumptive evidence of the presence of coliform bacteria. This medium can be used at
37°C for the detection of coliform organisms or at 44.5°C for the isolation of Escherichia coli from water and shellfish) or
45.5°C for foods.

When using sample more than 10 ml, the medium must be reconstituted at a concentration equivalent to that specified on the
ddirections, once the sample is added, the working procedure is as follows:

Transfer a loopful of culture from all the tubes of Lauryl Sulphate Broth (M080) showing gas formation within 24 hours and
from all the tubes showing xbacterial growth within 48 hours to EC Broth tubes. Within 30 minutes from the inoculum,
place the tubes in a water bath and incubate at 44°C for 24 hours. Consider the growth showing gas production as positive.
Calculate the density of the faecal coliform organisms by using MPN tables. False-negative reactions in recovering coliforms
from water supplies can occur due to low pH, refrigeration and use of bactericidal or bacteriostatic agents (8).
Gas formation at 44.5°C or 45.5°C (and 37°C) Escherichia coli, possibly also other coliforms.