Dermatophyte test medium: Difference between revisions

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Dermatophyte Test Medium

File:Dermatophyte test medium DTM positive.jpg

Dermatophyte Test Medium showing positive result

Dermatophyte Test Medium (DTM) is a specialized culture medium used in the field of dermatology and microbiology to isolate and identify dermatophytes, which are a type of fungi that cause skin infections known as dermatophytosis. These infections are commonly referred to as ringworm or tinea.

Composition

DTM is composed of a nutrient base that supports the growth of dermatophytes, along with indicators and inhibitors. The medium typically contains:

Sabouraud dextrose agar as the nutrient base.
Cycloheximide to inhibit the growth of non-dermatophyte fungi.
Chloramphenicol to inhibit bacterial growth.
Phenol red as a pH indicator.

The presence of phenol red allows for the detection of dermatophyte growth by a color change in the medium. Dermatophytes metabolize the nutrients in the medium, leading to an alkaline reaction that changes the color of the medium from yellow to red.

Procedure

To perform a dermatophyte test using DTM, the following steps are typically followed:

1. Sample Collection: A sample is collected from the infected area of the skin, hair, or nails using a sterile instrument. 2. Inoculation: The sample is inoculated onto the surface of the DTM. 3. Incubation: The inoculated medium is incubated at a temperature of 25-30°C for up to 14 days. 4. Observation: The medium is observed for growth and color change. A positive result is indicated by the growth of colonies and a color change to red.

Interpretation

A positive DTM result suggests the presence of dermatophytes. However, further identification of the specific species may require additional tests, such as microscopic examination or molecular techniques.

Applications

DTM is widely used in clinical laboratories for the diagnosis of dermatophytosis. It is a valuable tool for veterinarians and dermatologists in identifying the causative agents of fungal infections in both humans and animals.

Limitations

While DTM is effective in isolating dermatophytes, it has limitations:

False positives can occur due to the growth of non-dermatophyte fungi that also cause a color change.
Some dermatophytes may not grow well on DTM, requiring alternative methods for confirmation.

Related pages

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-'''Dermatophyte Test Medium''' (DTM) is a specialized [[Agar plate|agar medium]] used in [[Microbiology]] and [[Dermatology]] for the selective culture of [[dermatophytes]], a group of fungi that cause skin infections known as [[Tinea|tinea]] or ringworm in humans and animals. The medium contains ingredients that inhibit the growth of non-dermatophytic fungi and bacteria, while promoting the growth of dermatophytes. This allows for the easy identification and diagnosis of dermatophyte infections.
+{{DISPLAYTITLE:Dermatophyte Test Medium}}
+==Dermatophyte Test Medium==
+[[File:Dermatophyte_test_medium DTM_positive.jpg|thumb|right|Dermatophyte Test Medium showing positive result]]
+Dermatophyte Test Medium (DTM) is a specialized culture medium used in the field of [[dermatology]] and [[microbiology]] to isolate and identify [[dermatophytes]], which are a type of [[fungi]] that cause [[skin]] infections known as [[dermatophytosis]]. These infections are commonly referred to as [[ringworm]] or [[tinea]].
 ==Composition==
-Dermatophyte Test Medium comprises several key components:
+DTM is composed of a nutrient base that supports the growth of dermatophytes, along with indicators and inhibitors. The medium typically contains:
-* [[Antibiotics]] (usually [[Cycloheximide]] and [[Chloramphenicol]]) to suppress the growth of saprophytic fungi and bacteria.
-* [[Phenol red]] as a pH indicator, which changes color in the presence of dermatophytes due to the alkaline byproducts they produce.
+* [[Sabouraud dextrose agar]] as the nutrient base.
-* Nutrients to support the growth of dermatophytes, including sources of [[Carbon]] and [[Nitrogen]].
+* [[Cycloheximide]] to inhibit the growth of non-dermatophyte fungi.
+* [[Chloramphenicol]] to inhibit bacterial growth.
+* [[Phenol red]] as a pH indicator.
+The presence of phenol red allows for the detection of dermatophyte growth by a color change in the medium. Dermatophytes metabolize the nutrients in the medium, leading to an alkaline reaction that changes the color of the medium from yellow to red.
+==Procedure==
+To perform a dermatophyte test using DTM, the following steps are typically followed:
+. '''Sample Collection''': A sample is collected from the infected area of the skin, hair, or nails using a sterile instrument.
+. '''Inoculation''': The sample is inoculated onto the surface of the DTM.
+. '''Incubation''': The inoculated medium is incubated at a temperature of 25-30°C for up to 14 days.
+. '''Observation''': The medium is observed for growth and color change. A positive result is indicated by the growth of colonies and a color change to red.
+==Interpretation==
+A positive DTM result suggests the presence of dermatophytes. However, further identification of the specific species may require additional tests, such as microscopic examination or molecular techniques.
-==Mechanism==
+==Applications==
-The principle behind DTM's functionality lies in its selective inhibition and the pH indicator. Dermatophytes metabolize the nutrients in the medium, producing alkaline byproducts that cause the phenol red in the medium to shift from yellow to red. This color change is a positive indication of the presence of dermatophytes. Non-dermatophytic organisms, if they grow at all, do not produce a significant change in the medium's color.
+DTM is widely used in clinical laboratories for the diagnosis of dermatophytosis. It is a valuable tool for veterinarians and dermatologists in identifying the causative agents of fungal infections in both humans and animals.
-==Usage==
+==Limitations==
-DTM is widely used in veterinary and medical laboratories for the presumptive identification of dermatophyte infections. A sample from the infected area is placed on the medium and incubated at room temperature. A color change to red within a specified period, typically 14 days, suggests a positive result for dermatophytes. However, a definitive diagnosis may require further [[Microscopic examination|microscopic examination]] and [[Culture (microbiology)|culture]] identification.
+While DTM is effective in isolating dermatophytes, it has limitations:
-==Advantages and Limitations==
+* False positives can occur due to the growth of non-dermatophyte fungi that also cause a color change.
-The primary advantage of DTM is its ability to quickly and easily screen for dermatophyte infections. However, it is not without limitations. False positives can occur, and the medium does not differentiate between different species of dermatophytes. Additionally, some dermatophyte species may be inhibited by the antibiotics present in the medium.
+* Some dermatophytes may not grow well on DTM, requiring alternative methods for confirmation.
-==Conclusion==
+==Related pages==
-Dermatophyte Test Medium is a valuable tool in the diagnosis of dermatophyte infections. Its selective properties allow for the efficient identification of these fungi, facilitating timely and appropriate treatment. However, it should be used in conjunction with other diagnostic methods to ensure accuracy.
+* [[Dermatophytosis]]
+* [[Fungal culture]]
+* [[Microbiology]]
+* [[Sabouraud agar]]
 [[Category:Dermatology]]
 [[Category:Microbiology]]
-[[Category:Medical tests]]
-{{Medicine-stub}}