Development and Application of Rapid Antibiotic Resistance Analysis for Microbial Source Tracking in the Black River Watershed, Michigan

Abstract

Microbial source tracking (MST) is often a desirable component of water quality monitoring. To enable local health departments to utilize MST regularly, rapid methods need to be developed that can be performed without costly equipment, increased laboratory space, or advanced technical requirements. This paper describes the development, validation, and application of a rapid, small-scale MST method based on antibiotic resistance analysis. An automated plate reader allows for earlier and repeated measurements and can distinguish treatment effects after only six hours of incubation, compared with the overnight incubation for the conventional assay. Using this rapid MST assay, a known-source Escherichia coli (E. coli) antibiotic resistance pattern database was constructed for the Black River watershed in southeastern Michigan. The average rate of correct classification for the known-source database was 70.4% when comparing each of seven specific animal sources, 72.5% when comparing three generic animal groups (human, waterfowl, and livestock), and 88.9% when comparing human to non-human animal sources. The rapid assay and database were then used to identify the sources of E. coli at a public recreational beach as human (34%), goose (34%), and cattle (20%).