Cetrimide agar: Difference between revisions

Latest revision as of 05:29, 3 March 2025

Cetrimide agar is a selective growth medium used in microbiology for the isolation of Pseudomonas aeruginosa, a common Gram-negative, opportunistic pathogen. This medium is particularly useful in clinical and environmental microbiology for identifying and studying this bacterium due to its ability to inhibit the growth of other microorganisms while promoting the growth of P. aeruginosa.

Composition[edit]

Cetrimide agar contains several key components that make it selective for Pseudomonas aeruginosa:

Cetrimide: A quaternary ammonium compound that acts as a selective agent by inhibiting the growth of most other bacteria.
Magnesium chloride and potassium sulfate: These salts enhance the production of pyocyanin and fluorescein, pigments characteristic of P. aeruginosa.
Agar: A solidifying agent that provides a stable medium for bacterial growth.
Peptone: A source of nitrogen and other nutrients for bacterial growth.

Mechanism of Action[edit]

Cetrimide acts by disrupting the cell membranes of bacteria, which inhibits the growth of most Gram-positive and many Gram-negative bacteria. However, Pseudomonas aeruginosa is resistant to cetrimide due to its robust cell wall and efflux pump mechanisms, allowing it to thrive on this medium.

Identification of Pseudomonas aeruginosa[edit]

On cetrimide agar, Pseudomonas aeruginosa can be identified by its characteristic colony morphology and pigment production:

Colony Morphology: Colonies are typically flat, with a spreading edge and a metallic sheen.
Pigment Production: The production of pyocyanin (a blue-green pigment) and fluorescein (a yellow-green pigment) is enhanced, giving colonies a distinctive coloration under UV light.

Applications[edit]

Cetrimide agar is widely used in:

Clinical Microbiology: For the isolation and identification of Pseudomonas aeruginosa from clinical specimens such as wound swabs, sputum, and urine.
Environmental Microbiology: To detect Pseudomonas aeruginosa in water samples and other environmental sources.
Pharmaceutical Microbiology: In quality control testing to ensure the absence of Pseudomonas aeruginosa in non-sterile pharmaceutical products.

Limitations[edit]

While cetrimide agar is effective for isolating Pseudomonas aeruginosa, it is not suitable for differentiating between different strains of Pseudomonas. Additional biochemical tests and molecular methods are required for further characterization.

Related Pages[edit]

Pseudomonas aeruginosa pigment

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-== Cetrimide Agar ==
+'''Cetrimide agar''' is a selective growth medium used in microbiology for the isolation of ''[[Pseudomonas aeruginosa]]'', a common Gram-negative, opportunistic pathogen. This medium is particularly useful in clinical and environmental microbiology for identifying and studying this bacterium due to its ability to inhibit the growth of other microorganisms while promoting the growth of ''P. aeruginosa''.
-'''Cetrimide agar''' is a type of [[growth medium]] used in [[microbiology]] for the selective isolation and identification of [[Pseudomonas aeruginosa]], a common [[Gram-negative]] bacterium. This medium is particularly useful in clinical and environmental microbiology for detecting this pathogen in various samples.
+== Composition ==
+Cetrimide agar contains several key components that make it selective for ''Pseudomonas aeruginosa'':
-=== Composition ===
+* '''Cetrimide''': A quaternary ammonium compound that acts as a selective agent by inhibiting the growth of most other bacteria.
-Cetrimide agar contains several key components that make it selective for Pseudomonas aeruginosa:
+* '''Magnesium chloride and potassium sulfate''': These salts enhance the production of pyocyanin and fluorescein, pigments characteristic of ''P. aeruginosa''.
+* '''Agar''': A solidifying agent that provides a stable medium for bacterial growth.
+* '''Peptone''': A source of nitrogen and other nutrients for bacterial growth.
-* '''Cetrimide''': A quaternary ammonium compound that acts as a selective agent by inhibiting the growth of most other bacteria, allowing Pseudomonas aeruginosa to thrive.
+== Mechanism of Action ==
-* '''Magnesium chloride and potassium sulfate''': These salts enhance the production of pyocyanin, a blue-green pigment characteristic of Pseudomonas aeruginosa.
+Cetrimide acts by disrupting the cell membranes of bacteria, which inhibits the growth of most Gram-positive and many Gram-negative bacteria. However, ''Pseudomonas aeruginosa'' is resistant to cetrimide due to its robust cell wall and efflux pump mechanisms, allowing it to thrive on this medium.
-* '''Peptone''': Provides essential nutrients for bacterial growth.
-* '''Agar''': A solidifying agent that provides a surface for bacterial colonies to grow.
-=== Mechanism of Action ===
+== Identification of ''Pseudomonas aeruginosa'' ==
-Cetrimide agar works by exploiting the natural resistance of Pseudomonas aeruginosa to cetrimide. The medium's high salt concentration and the presence of cetrimide inhibit the growth of most other bacteria, while Pseudomonas aeruginosa can grow and produce its characteristic pigments, such as pyocyanin and fluorescein.
+On cetrimide agar, ''Pseudomonas aeruginosa'' can be identified by its characteristic colony morphology and pigment production:
-=== Uses ===
+* '''Colony Morphology''': Colonies are typically flat, with a spreading edge and a metallic sheen.
-Cetrimide agar is primarily used in:
+* '''Pigment Production''': The production of pyocyanin (a blue-green pigment) and fluorescein (a yellow-green pigment) is enhanced, giving colonies a distinctive coloration under UV light.
-* [[Clinical microbiology]]: For the isolation of Pseudomonas aeruginosa from clinical specimens such as [[sputum]], [[urine]], and [[wound]] swabs.
+== Applications ==
-* [[Environmental microbiology]]: To detect Pseudomonas aeruginosa in water samples and other environmental sources.
+Cetrimide agar is widely used in:
-* [[Pharmaceutical microbiology]]: To ensure the absence of Pseudomonas aeruginosa in non-sterile pharmaceutical products.
-=== Procedure ===
+* '''Clinical Microbiology''': For the isolation and identification of ''Pseudomonas aeruginosa'' from clinical specimens such as wound swabs, sputum, and urine.
-. Prepare the cetrimide agar according to the manufacturer's instructions.
+* '''Environmental Microbiology''': To detect ''Pseudomonas aeruginosa'' in water samples and other environmental sources.
-. Sterilize the medium by autoclaving.
+* '''Pharmaceutical Microbiology''': In quality control testing to ensure the absence of ''Pseudomonas aeruginosa'' in non-sterile pharmaceutical products.
-. Pour the medium into sterile Petri dishes and allow it to solidify.
-. Inoculate the sample onto the surface of the agar.
-. Incubate the plates at 35-37°C for 24-48 hours.
-. Examine the plates for the presence of characteristic colonies of Pseudomonas aeruginosa, which appear as blue-green or yellow-green due to pigment production.
-=== Limitations ===
+== Limitations ==
-While cetrimide agar is effective for isolating Pseudomonas aeruginosa, it is not entirely specific. Some other Pseudomonas species and non-Pseudomonas bacteria may also grow on this medium. Therefore, further biochemical tests are often required to confirm the identity of the organism.
+While cetrimide agar is effective for isolating ''Pseudomonas aeruginosa'', it is not suitable for differentiating between different strains of ''Pseudomonas''. Additional biochemical tests and molecular methods are required for further characterization.
-== Also see ==
+== Related Pages ==
 * [[Pseudomonas aeruginosa]]
 * [[Microbiological culture]]
-* [[Selective media]]
+* [[Selective medium]]
-* [[Pyocyanin]]
-{{Microbiology}}
-{{Bacteriology}}
 [[Category:Microbiological media]]
-[[Category:Microbiology]]
+[[Category:Pseudomonas]]
+<gallery>
+File:P-aeruginosa pigment.jpg|Pseudomonas aeruginosa pigment
+</gallery>