Remarks

1. The temperature of water bath must be at 100oC to

liquefy the media. Cooler waterbaths will provide

lumpy, uneven media.

2. Since, all agar-based media solidify rapidly, it is

important that the minimum time be lost between

retrieval of the pouch from boiling water bath and

pouring aseptically into the sterile plates. This will

produce evenly surfaced medium.

3. The poured plates on solidification can be used for

plating specimens or for antibiotic susceptibility tests

(Mueller Hinton Agar).

4. Good laboratory practices and hazard precautions

must be observed at all times.

5. With CLED medium, use 10 µL urine inoculum and

observe the growth at 24 hours. The colony count

multiplied by 100 will correspond to CFU/mL of

organism in the urine sample.

6. 15 mL media is sufficient for the standard 90 mm petri

dishes. In case smaller petri dishes are being used

more number of plates can be poured with a single

pouch, proportionately.

7. The identity of the medium is imprinted on the sealing

band as a product code, whereas the lot number is

mentioned on the carton label.

Troubleshooting

Problem: Smooth gelled media not formed

Possible causes Solutions

1. Water bath not maintained at 100°C Water bath should be maintained at 100°C

2. Time period at 100°C is less than 10 minutes Ensure pouched media is kept for 10 minutes in boiling water bath

3. Maximum time lost between retrieval of Minimum time should be lost between retrieval of the pouch from boiling water

the pouch from the boiling water and bath and pouring aseptically into sterile plates, i.e. not more than 5 minutes

pouring aseptically into sterile plates

4. Vibration/Shaking of surface during Pour the plates on a firm surface not prone to vibration or shaking

gelling of the media

TABLE 27.1: Colony characteristics on CLED and MacConkey Agar

Medium Morphology E. coli Proteus Klebsielia Candida Pseudomonas Salmonella Shigella Streptococci Staphyloccocci

CLED Colonies Pink

regular

Green

irregular

Dull

large

mucous

White

regular

Colorless

Convex

- - Pink regular Pink regular