Highly specific sewage-derived Bacteroides qPCR assays target sewage polluted waters.

The identification of sewage contamination in water has primarily relied on detection of the human Bacteroides using markers within the V2 region of the 16S ribosomal RNA (rRNA) gene. Despite establishment of multiple assays that target the HF183 cluster (i.e., Bacteroides dorei) and other Bacteroides organisms (e.g., Bacteroides thetaiotomicron), the potential for more human-associated markers in this genus has not been explored in depth. We examined Bacteroides population structure in sewage and animal hosts across the V4V5 and V6 hypervariable regions. Using near full-length cloned sequences, we identified the sequences in the V4V5 and V6 hypervariable regions that are linked to the HF183 marker in V2 region and found these sequences were present in multiple animals. In addition, the V4V5 and V6 regions contained human fecal marker sequences for organisms that were independent of HF183 cluster. The most abundant Bacteroides in untreated sewage was not human associated but pipe derived. Two TaqMan qPCR assays were developed targeting the V4V5 and V6 regions of this organism. Validation studies using fecal samples from seven animal hosts (n=76) and uncontaminated water samples (n=30) demonstrated their high specificity for sewage. Freshwater Bacteroides were also identified in uncontaminated water samples, demonstrating that measures of total Bacteroides do not reflect fecal pollution. Comparison of two previously described human Bacteroides assays (HB and HF183/BacR287) in municipal wastewater influent and sewage contaminated urban water samples produced identical results, illustrating they target the same organism. Detection of sewage-derived Bacteroides provided an independent measure of sewage-impacted waters. [ABSTRACT FROM AUTHOR]