Easy DryTM are absorbent pads saturated with a sterile, dehydrated culture medium. Each pad is pre-plated in a Petri dish and is immediately ready to use after pouring sterile distilled or deionized water on it. Easy DryTM are optimal for the examination of large sample volumes by the membrane filter method.
Easy DryTM TBX is a chromogenic selective medium used for the isolation, identification and enumeration of β-glucuronidase-positive Escherichia coli in foodstuffs, animal feed and water. This medium complies with the recommendations of ISO 16649-1.
PREPARATION
1.
Cut open a bag and remove the number of Easy Dry plates needed.
2.
Moisten the pad contained
in the Petri dish with 2.2 ml of sterile distilled or deionized water.
3.
Wait 5 minutes before
using.
TEST PROCEDURE
For the recovery of sub-lethally injured E. coli, a resuscitation step is recommended by ISO 16649-1:
Place a membrane filter onto the dried surface of a plate of Mineral-Modified Glutamate Agar (MMGA). Spread 1 ml of the test sample evenly over the whole membrane surface and incubate at 37°C for 4 ± 1 h.
Under the same conditions, using decimal dilutions of the test sample or of the initial suspension, two plates per dilution are inoculated.
After resuscitation, transfer the membrane from MMGA to a plate containing a just rehydrated pad of Easy DryTM TBX. Incubate aerobically at 44°C for further 18-24 h.
INTERPRETING RESULTS
After
incubation observe the color of the
colonies and interpret the results as
indicated in the ID table.
ID Table.
|
Microorganism |
Typical colony color |
|
β-glucuronidase-positive Escherichia coli |
Blue to blue-green |
|
β-glucuronidase-negative bacteria (if not inhibited) |
White to green-beige |
Count the typical colony-forming units (CFU) of β-glucuronidase-positive Escherichia coli in each plate containing less than 150 typical CFU and less than 300 total (typical and non-typical) CFU.
Note: β-glucuronidase-negative E. coli strains form colorless colonies on this medium, e.g. E. coli O157, or they cannot grow at elevated temperature of 44°C, e.g. E. coli O157:H7.
Typical reactions for confirmation of E. coli are a positive indole-reaction as well as a negative oxidase- and catalase-reaction.
APPEARANCE OF THE MEDIUM
Whitish pad. Yellowish once rehydrated.
STORAGE
Store at 10-25°C away from light. Do not
use the product beyond its expiry date on the label or if product shows any
evidence of contamination or any sign of deterioration.
SHELF LIFE
2 years.
