Pseudalert 250*

24-hour detection of Pseudomonas aeruginosa

Delivers definitive results with no additional confirmation steps.
Minimizes the risk of false positives from non-target organisms.
Same easy-to-use platform as the Colilert 250 test.

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Overview

Easy

Blue fluorescence indicates a positive result.
Same familiar platform as the Colilert 250 test:Ready-to-use reagents, no media preparation.
Convenient unit-dosed packaging.
No toxic compounds.

Rapid

Definitive results in 24 hours.
Less than 1 minute of hands-on time for streamlined testing work flow.

Accurate

Specifically detects Pseudomonas aeruginosa, reducing the risk of false positives from non-target organisms.
Results are definitive without additional confirmation steps.
Simple blue fluorescent change minimizes subjective result interpretation.
Liquid enrichment optimizes recovery.

Science

How the Pseudalert 250 test works

The Pseudalert 250 test detects the presence of Pseudomonas aeruginosa in bottled water samples.

The test is based on a bacterial enzyme detection technology that signals the presence of P. aeruginosa through the hydrolysis of a substrate in the Pseudalert 250 reagent. P. aeruginosa cells rapidly grow and reproduce using the rich supply of amino acids, vitamins, and other nutrients present in the Pseudalert 250 reagent. Actively growing strains of P. aeruginosa have an enzyme that cleaves the substrate in the reagent to produce blue fluorescence under ultraviolet light.

The Pseudalert 250 test detects P. aeruginosa at 1 cfu per 250 mL sample within 24 hours.

How to use

Presence/Absence

Step 1

Add reagent to sample (sample will turn yellow), and then incubate at 38°C ± 0.5°C for 24–28 hours.

Step 2

Read under ultraviolet (UV) light. Blue fluorescence indicates presence of P. aeruginosa. See the Pseudalert Quick Reference Guide for tips on reading fluorescence:
Pseudalert Quick Reference Guide

Frequently asked questions

The Pseudalert 250 test is designed specifically for bottled water samples. Bottled water samples are defined as samples taken from any point in the manufacturing of bottled water (from the original water to the finished product). The Pseudalert 250 test was specifically formulated and tested to ensure it would detect stressed P. aeruginosa in these samples.

The Pseudalert 250 test is based on a bacterial enzyme detection method that signals the presence of Pseudomonas aeruginosa through the hydrolysis of an enzyme substrate. P. aeruginosa cells rapidly grow and reproduce using the rich supply of amino acids, vitamins, and other nutrients present in the Pseudalert reagent. Actively growing strains of P. aeruginosa have an enzyme that cleaves the substrate in the reagent to produce blue fluorescence under ultraviolet light. The Pseudalert 250 test detects P. aeruginosa at 1 cfu per 250 mL sample within 24 hours.

The Pseudalert 250 test detects Pseudomonas aeruginosa at 1 cfu per 250 mL.

There is no comparator for the Pseudalert 250 test. For comparison, use a negative control when interpreting results.

Water samples are incubated at 38°C ± 0.5°C for 24 hours, and results are valid up to 28 hours.

No. Breakthrough of non-target organisms can occur at temperatures other than 38°C ±0.5°C.

Yes, if the results are positive. An inoculated Pseudalert test presence/absence sample that is positive for Pseudomonas aeruginosa before 24 hours is a confirmed positive test for P. aeruginosa. However, for an accurate quantitative determination of P. aeruginosa in a sample, the results should be read at 24–28 hours of incubation.

Yes, if the results are negative. If an inoculated Pseudalert test sample is inadvertently incubated for over 28 hours, lack of blue fluorescence is a valid negative test result. However, blue fluorescence that develops after 28 hours is not a valid positive test result; the test should be repeated or verified.

For presence/absence testing, use a sterile, transparent, non-fluorescing vessel. For the Quanti-Tray and Quanti-Tray/2000 systems, any sterile vessel can be used.

Store the Pseudalert 250 test at 2°C–30°C away from light.

The Pseudalert 250 reagent powder should be tan in color; it should be dry and free-flowing. Any concerns about the color or integrity of the reagent powder should be directed to IDEXX Technical Support at +1-800-321-0207 or by email at water@idexx.com.