Isolation Techniques and Selective Media, A Photographic Atlas for the Microbiology Laboratory, Pseudomonas Isolation Agar
Purpose
Pseudomonas Isolation Agar (PIA) is a selective and differential medium used to isolate nonfermenting Gram-negative bacteria in clinical samples, especially Pseudomonas species.
It also allows differentiation of P. aeruginosa, a major cause of nosocomial infections (often from contamination of hospital equipment), from other pseudomonads based on its production of the pigment pyocyanin.
Principle
The fatty acid synthesis inhibitor, Irgasan®1 (also known as Triclosan), is inhibitory to many Gram-positive and Gramnegative species. Pseudomonas species are not affected by its activity (at its concentration in the medium) due to a membrane efflux pump. Carbon and nitrogen are provided by peptone and glycerol. Pyocyanin production is promoted by potassium sulfate, magnesium chloride, and glycerol.
2-25 PSEUDOMONAS ISOLATION AGAR Pseudomonas aeruginosa
is on the left; P. fluorescens is on the right. Notice the greenish color of
P. aeruginosa due to the pigment pyocyanin
Suggested Reading
- Michael J. Leboffe & Burton E. Pierce. A Photographic Atlas for the Microbiology Laboratory 4th edition 2011
COMMENTS