Sensitive detection of E. coli in artificial seawater by aptamer-coated magnetic beads and direct PCR

Abstract

Foodborne and waterborne E. coli remains a major economic burden worldwide. Assaying seawater for trace levels of E. coli is challenging since it applies time-consuming preparations, expensive instrumentation and complicated procedures. Therefore, there is a continued demand for new analytical technologies that can detect low bacterial concentrations in a more cost- and time-effective manner. In this study, combination of E. coli pre-concentration with a direct polymerase chain reaction (PCR) was shown to enable rapid bacterial detection without enrichment step or DNA extraction/purification. The E1 aptamer that targets E. coli surface epitope grafted onto magnetic beads efficiently concentrated E. coli from water samples containing high concentration of NaCl. When direct PCR was performed on bacteria attached to these aptamer-modified magnetic beads, a limit of 103 CFU/mL was obtained. The overall analysis was performed in less than 3 h. This approach may lead to a future PCR-based biosensor system for online monitoring of enteric bacteria in seawater.