VRBGA/TSA dipslide is a ready-to-use device with two different media coated onto a plastic support used for the microbial monitoring of surfaces and liquids. VRBGA (Violet Red Bile Glucose Agar) is a selective medium which allows the isolation and enumeration of Enterobacteriaceae . TSA (Tryptic Soy Agar) is a nonselective medium which supports growth of most non fastidious organisms.

TEST PROCEDURE

1. Take a slide from the refrigerator and leave it at ambient temperature for about 5 minutes.
2. Unscrew and extract the slide from its cylindrical container. Avoid any contact with the agar surface.
3. For surface monitoring, flex the cap forming a 90° angle and press each side of the slide firmly against the surface to be examined for 10 seconds. Alternatively, use a swab for sampling the area, afterwards roll the swab gently over the agar surface. For examination of liquids, hold the slide by the cap and immerse it completely into the test fluid.
4. Reinsert the slide into its tube, screw it tight and incubate at 37 ± 1°C for 24-48 hours. Some organisms, such as mesophilic bacteria, may require a longer incubation (3 to 5 days) at 30-35°C to show visible growth on TSA.

RESULTS INTERPRETATION

Count the total number of colonies on TSA (Side 1) to obtain the total aerobic microbial count. Enterobacteriaceae ferment glucose forming pink to red colonies (with or without precipitation haloes) on VRBGA (Side 2).

For surface testing, the colony count on each agar side can be calculated into CFU per cm² as follows: CFU (actual count) / 12.5 cm² = CFU/cm²

APPEARANCE

Side 1. Slightly opalescent, light amber.

Side 2. Very slightly to slightly opalescent, reddish-purple.

STORAGE CONDITIONS

10-25°C away from light, until the expiry date on the label. Eliminate if signs of deterioration or contamination are evident.

SHELF LIFE

9 months