Broader incubation temperature tolerances for microbial drinking water testing with enzyme substrate tests

Area of Science:

• Environmental microbiology
• Water quality analysis
• Microbial detection methods

Background:

• Microbiological testing is crucial for safe drinking water.
• Resource limitations, such as specialized labs and controlled temperatures, hinder testing in some areas.
• Enzyme substrate tests offer potential for simpler water quality monitoring.

Purpose of the Study:

• To evaluate the performance of two enzyme substrate tests (Colilert and Aquatest) for detecting E. coli and total coliforms at varied incubation temperatures.
• To determine if these tests provide consistent results outside the currently specified temperature ranges.
• To assess the feasibility of broader temperature use for E. coli detection in drinking water.

Main Methods:

• Examined the recovery of chlorine-injured and wild-type E. coli using Colilert and Aquatest.
• Incubation temperatures were varied, with comparisons made to the standard 37 °C ± 1.
• Performance was assessed by comparing microbial enumeration across different temperature conditions.

Main Results:

• Colilert showed no impairment in recovering chlorine-injured E. coli between 33-39 °C.
• Aquatest demonstrated reliable recovery of E. coli within a broader range of 31-43 °C.
• Both enzyme substrate tests maintained performance over wider temperature ranges than currently specified.

Conclusions:

• Enzyme substrate tests like Colilert and Aquatest can reliably detect E. coli and coliforms across a wider temperature spectrum.
• This flexibility in incubation temperature can enhance the accessibility and practicality of water quality testing, especially in low-resource settings.
• The findings support the use of these tests under non-standard temperatures, potentially improving global drinking water safety surveillance.