Membrane Filter Technique for Enumeration of Pseudomonas aeruginosa

A membrane filter procedure for the quantitation of Pseudomonas aeruginosa (mPA procedure) has been developed. Through the use of inhibitors and an elevated incubation temperature, the level of background microbial flora was decreased approximately 10,000-fold. Using P. aeruginosa cells suspended in sea water and held for 24 hr, between 70 and 100% of the "viable" cells could be recovered by the mPA procedure. Assay variability was found to be insignificant. The recoveries of P. aeruginosa from surface (fresh and salt) waters, potable waters, and sewage by the mPA procedure exceeded those obtainable by current methods. Subsequent to its development and evaluation, the mPA procedure was used at three other laboratories for the enumeration of P. aeruginosa in potable and recreational waters and in sewage samples. It was found amenable to routine use, and confirmation of typical colonies approached 100%.