Published: 11th Feb 2026, 18:16

Every microbiology laboratory has times when accuracy is more important than anything else. A urine sample arrives with a suspicion of urinary tract infection, and the culture needs to be clean, easy to read and reliable. That’s where the choice of medium becomes crucial. This is where CLED Agar silently earns itself a place in the routine diagnostic microbiology.

Unlike selective media that inhibit growth of bacteria, CLED Agar is a nutritionally balanced medium which supports the growth of the majority of urinary pathogens and also avoids common complications such as Proteus swarming. For microbiologists who are handling urine cultures daily, this medium is a reliable choice. It helps achieve uniform colony growth.

From hospital laboratories that need to process large numbers of samples to diagnostic centers focusing on accuracy, CLED Agar is a reliable foundation for urinary bacteriology.

What is CLED Agar?

CLED Agar is a differential, non-selective culture medium primarily employed for the isolation and enumeration of bacteria in urine.

The CLED Agar full form is Cystine Lactose Electrolyte Deficient Agar, it is the name that describes the purpose of the culture medium. This medium is used to grow Gram-positive and Gram-negative organisms that are typically associated with urinary tract infections. Lactose fermenters and non-lactose fermenters are separated by lactose fermentation and the electrolyte-deficient formulation inhibits swarming of Proteus spp., which results in well isolated colonies. Because of these characteristics, it is employed as a general purpose medium for the processing of urine culture in the clinical microbiology laboratory.

CLED Agar Composition

The reliability of CLED Agar comes from its carefully selected ingredients that create a nutritionally supportive yet controlled environment.

All the components contribute to the growth, differentiation, and clarity required for accurate interpretation of urinary pathogens.

Principle of CLED Media

The working principle of CLED Media is based on selective nutrient balance and differential indicators:

• Peptones contain nitrogen, amino acids, and other growth factors that are required for the growth of bacteria.
• Lactose is a fermentable carbohydrate substrate that allows differentiation between lactose fermenting and non-lactose fermenting organisms.
• Bromothymol blue is a pH indicator that changes colour to indicate the production of acid during the fermentation of lactose.
• Deficiency of electrolytes prevents the swarming of Proteus spp., permitting discrete colonies.
• L-cystine stimulates the growth of cystine-dependent bacteria and recovery of such bacteria is improved.

All of these factors make it a convenient and effective medium for urine bacteriology.

Instructions for Use

For optimal performance of CLED Agar, standard preparation steps should be followed:

1. Dissolve 36 g of dehydrated medium in 1000 ml of distilled water.
2. Heat gently with frequent mixing until the medium dissolves completely.
3. Autoclave at 121°C for 15 minutes.
4. Cool the medium to 45-50°C.
5. Pour into sterile Petri plates under aseptic conditions.

Once solidified, it looks greenish because of the bromothymol blue indicator and it gives a flat surface for streaking of the urine sample.

Interpretation of Results

After incubation, CLED Agar allows clear visual differentiation of organisms based on lactose fermentation:

Such predictable results make it suitable for routine diagnostic workflows.

CLED Agar Uses in Microbiology

Among the many CLED Agar uses, the most prominent is routine urine culture testing. The medium is widely applied for:

• Isolation and differentiation of urinary tract pathogens
• Semi-quantitative urine culture analysis
• Prevention of Proteus swarming
• Routine screening in clinical diagnostic laboratories

Because of its clarity and consistency, CLED Agar continues to be recommended for primary isolation in urinary bacteriology.

Why Choose CLED Agar from TM Media?

Not all Culture Media give uniform results. CLED Agar (TMP 014) is designed to meet the needs of routine diagnostic laboratory:

• Pharmacopoeia-grade quality produced under stringent control
• Excellent differentiation between lactose fermenters and non-fermenters
• Batch-tested consistency to ensure dependable performance
• Stable for long life under recommended conditions

Reliable performance was essential for laboratories that process urine samples on a daily basis. CLED Agar from TM Media delivers accurate diagnosis with no compromise.

Conclusion

In microbiology, dependable diagnosis starts with the correct Culture Medium. CLED Agar is a trusted medium for urine culture. It has a balanced formulation, clearly differentiates bacteria, and inhibits Proteus swarming. It supports a wide range of urinary pathogens while maintaining clarity, making it indispensable in clinical laboratories.

When prepared, stored, and used properly, it gives consistent results that support accurate clinical decisions. This medium remains a reliable and easy choice for routine urinary bacteriology in diagnostic microbiology.

Frequently Asked Questions (FAQs)

Q1. Can antibiotics be added to CLED Agar?

A. It is rarely added with antibiotics. Adding antimicrobial agents could influence its differential characteristic and recovering yields might be altered.

Q2. Does CLED Agar support anaerobic bacteria?

A. No

Q3. What happens if we incubate CLED Agar for longer than the recommended time?

A. Prolonged incubation may alter the appearance of the colonies or result in colour changes due to metabolic alterations. To avoid misinterpretation, observe within the recommended incubation time of 18-24 hours.

Q4. Does CLED Agar prevent Proteus swarming?

A. Yes, the deficiency of electrolytes prevents Proteus swarming.

Q5. What Affects CLED Agar performance.

A. Effectiveness may be influenced by inadequate sterilization, poor preparation, dehydration of plates or by using expired media.