Development of a rapid and cost-effective paper strip dip test for visual detection of coliforms and catalase-positive bacteria in water samples

Abstract

Ensuring safe drinking water is fundamental to public health, which necessitates effective detection of bacterial contamination in water. To ease the bacterial monitoring in low-resource settings, this study has developed a breakthrough colorimetric paper strip dip (PSD) test for the qualitative and quantitative monitoring of bacterial contamination. The test relies on Fenton chemistry where dye-coated paper strips are immersed in a solution of water sample and hydrogen peroxide (H₂O₂). The bacterial catalase in contaminated water competes with the Fenton catalyst for F, resulting in a visible color change in both the strip and the sample solution. The intensity of the decolorization on the strip/solution determines the bacterial contamination in the water sample. This test has reached detection limits of 20, 40, and 35 CFU/mL for Escherichia coli, Citrobacter youngae, and Pseudomonas aeruginosa, respectively, in spiked water samples within 5 min. The PSD test offers a high sensitivity of 0.477, 0.379, and 0.601 ΔE^⁎/dec for E. coli, C. youngae, and P. aeruginosa, respectively. The reliability of the test is demonstrated by its low susceptibility to interference from potential contaminants present in natural drinking water sources during bacterial detection. Furthermore, the test is integrated with a mobile app that interrelates color on the strip with bacterial contamination in water samples and recommends the extent of disinfection required based on the result. Thus, the PSD test offers an ideal solution for on-site bacterial detection, characterized by its rapidity, precision, specificity, cost-effectiveness (∼0.060 USD per test), and ease of operation.