DTM Agar Base (Dermatophyte Test Medium Base)

DTM Agar Base (Dermatophyte Test Medium Base)

CAT No.: AS-1412
HS Code: 38210000

Product Overview

DTM Agar Base (Dermatophyte Test Medium Base) is a selective and differential culture medium formulated for the isolation and presumptive identification of dermatophytes from clinical, veterinary, and environmental specimens.

The medium supports the growth of:

• Trichophyton spp.

• Microsporum spp.

• Epidermophyton spp.

while suppressing contaminating bacteria and saprophytic fungi when used with Ausamics CCG Selective Supplement.

A characteristic yellow → pink/red color change due to alkaline metabolite production enables rapid presumptive detection of dermatophyte growth.

Composition (per liter)

• Soya Peptone — 10.0 g

• Dextrose (Glucose) — 10.0 g

• Phenol Red — 0.2 g

• Agar — 20.0 g

Final pH (25°C): 5.5 ± 0.2

Formula optimized for consistent dermatophyte recovery and performance.

Preparation (For 500 mL Medium)

1. Suspend 20.1 g of dehydrated medium in 500 mL purified or distilled water.

2. Heat with agitation until completely dissolved.

3. Autoclave at 121°C for 15 minutes.

4. Cool to 45–50°C.

5. Aseptically add Ausamics CCG Selective Supplement (ASS-2556):

   • Reconstituted according to supplement instructions

   • Final concentrations in 500 mL prepared medium:

     • Cycloheximide: 250 mg (0.5 g/L)

     • Chlortetracycline: 50 mg (0.1 g/L)

     • Gentamicin: 50 mg (0.1 g/L)

6. Mix gently but thoroughly.

7. Pour into sterile Petri plates under aseptic conditions.

Allow plates to solidify and store at 2–8°C.

Principle of the Medium

Dermatophytes metabolize protein substrates and produce alkaline by-products. These raise the pH of the medium, causing phenol red to change from:

Yellow → Pink/Red

This color reaction allows rapid presumptive differentiation from non-dermatophyte molds.

Selective antibiotics inhibit:

• Gram-positive bacteria

• Gram-negative bacteria

• Yeasts

• Rapid-growing saprophytic molds

Performance Characteristics

Rapid growers may produce visible color change within 3 days.
Slow-growing species may require extended incubation.

Specimen Types

• Skin scrapings

• Hair fragments

• Nail clippings

• Scalp scales

Follow standard clinical microbiology specimen collection guidelines.

Appearance

Dehydrated medium: Light yellow to pink, homogeneous free-flowing powder
Prepared medium: Orange-red, slightly opalescent gel

Storage & Shelf Life

Dehydrated medium:

• Store at 10–30°C

• Keep tightly closed

• Protect from moisture

Prepared plates:

• Store at 2–8°C

• Avoid prolonged exposure to light

Use before expiry date stated on label.

Limitations

• False positives may occur after prolonged incubation (>6 days).

• Heavy contamination may cause non-dermatophytes to produce delayed alkalinization.

• Confirmatory testing (microscopy and biochemical identification) is recommended for definitive diagnosis.

Safety & Handling

• For in vitro diagnostic use only.

• Use appropriate PPE (gloves, lab coat, eye protection).

• Follow standard microbiological safety practices.

• Autoclave all contaminated materials before disposal.

Refer to Safety Data Sheet (SDS) for hazard classification of supplements.

Product image is for illustrative purposes only. Actual appearance, packaging, or labeling may differ.