A comparison of ARA and DNA data for microbial source tracking based on source-classification models developed using classification trees

The literature on microbial source tracking (MST) suggests that DNA analysis of fecal samples leads to more reliable determinations of bacterial sources of surface water contamination than antibiotic resistance analysis (ARA). Our goal is to determine whether the increased reliability, if any, in library-based MST developed with DNA data is sufficient to justify its higher cost, where the bacteria source predictions are used in TMDL surface water management programs. We describe an application of classification trees for MST applied to ARA and DNA data from samples collected in the Potomac River Watershed in Maryland. Conclusions concerning the comparison of ARA and DNA data, although preliminary at the current time, suggest that the added cost of obtaining DNA data in comparison to the cost of ARA data may not be justified, where MST is applied in TMDL surface water management programs.