Background: For the water analysis, for Pseudomonas aeruginosa a presumptive positive result can be achieved in 40- 48 hours using the traditional membrane filtration technique followed by an additional 24-48 hour confirmation stage. Conversely, the Pseudalert Quanti-Tray™ method can give confirmed results after 24-28 hours. In this case, actively growing strains of Pseudomonas aeruginosa show a confirmed positive result when a specific enzyme cleaving the substrate in the reagent produces a blue fluorescence under 365 nm ultraviolet light. A comparison of the performance of the Pseudalert respect to the standard method was conducted using statistical methods.
Methods: Drinking water was analyzed in parallel with the membrane filtration technique using Pseudomonas CN agar (UNI EN ISO 16266) and the Pseudalert. Confirmation test are requested by the standard method and although Pseudalert Quanti-Tray™ gives confirmed results, all the positive isolates were also confirmed. Data were analyzed by statistical methods.
Results: For drinking water, Pseudalert showed a very high sensitivity (98,8%) and a high percentage of specificity (96,8%). From a total of 889 positive isolates, a very high confirmation rates (99,3%) was calculated. Statistical analyses confirmed that the two methods were not statistically different.
Conclusions: These results indicate that the Pseudalert produces confirmed results in a shorter time than the standard reference method allowing the detection of Pseudomonas aeruginosa with no further confirmation steps. It could be a valid alternative method for the water analysis.