Abstract:
Reducing the burden of water-related illness requires better monitoring for fecal contamination so that risks can be identified and controlled. Currently used tests do not provide rapid feedback on drinking water risks, are often bulky and expensive, and are not well suited for field use. We developed a novel test method based on a specific antigen/antibody reaction to create a visual indication of the presence of E. coli; in a water sample. We used a latex agglutination technique employing E. coli; specific antibody coated microparticles (MPs) as an identification method, preceded by a recovery step and growth period to enhance concentrations to detectable levels. E. coli; in laboratory prepared waters were recovered via membrane filtration, grown to titers sufficient for MP use, and interacted with MPs to provide a quantal (presence/absence). The growth rate of E. coli; in liquid media after concentration by membrane filtration was investigated, as well as the role of elution of E. coli; from the membrane filter. The detection limit of antibody coated microparticles was also determined. Results showed low correlation (-0.150) between average recovery rate and average 0 - 6 hour doubling time, indicating low need for bacterial elution. The subsequent growth step yielded an average replication of 660,000 the original membrane filter count at 9 hours, with an average doubling time in log phase growth of 21.5 minutes. Results suggest a lower detection limit of approximately 13,000,000 cfu/mL for E. coli; using antibody coated microparticles. Coupled together, the test can positively detect a single E. coli; cfu in the original sample after incubation for 11 hours (95% CI). Required minimum incubation times for detection of 10 cfu and 100 cfu were 9 hours 50 minutes, and 8 hours 40 minutes (95% CI), respectively. The novel method provides a promising method of decreasing both the cost of field water testing and time required to provide results. Doing so would greatly improve the ability to identify and reduce the effect of fecal contamination in drinking water sources.
