Q-257. Survival and Persistence of Human- and Ruminant-Specific Fecal Bacteroidales in Freshwater Microcosms

S. P. Walters1, K. G. Field2;
1Stanford Univ., Stanford, CA, 2Oregon State Univ., Corvallis, OR.

Background: Standard indicators of fecal pollution in water, Escherichia coli and fecal enterococci, can persist and grow in the environment. Alternatively, PCR of host-specific markers from Bacteroidales fecal anaerobes can identify fecal pollution and discriminate its source. We previously found inconsistencies between E. coli and host-specific markers in natural waters, suggesting that factors controlling persistence and growth of fecal indicators differ from those influencing presence of Bacteroidales markers. Objective: Our objective was to measure marker persistence and cell survival of two human (HF134, HF183) and two ruminant (CF128, CF193) fecal Bacteroidales markers, compared to E. coli and enterococci. Methods: Freshwater microcosms were inoculated with fresh cattle or human feces and incubated at a relevant stream temperature (13 °C) in natural light or darkness. Marker persistence was measured by PCR and QPCR. Survival of Bacteroidales marker cells was measured by RT-qPCR. Results: E. coli concentrations (MPN/100 ml) were above established limits for recreational water throughout the experiment. Enterococci numbers and survival depended on fecal source and light exposure; enterococci fell below established limits by 14 days in both human and cattle fecal microcosms. Ruminant-specific Bacteroidales markers survived and persisted through 14 days, but had differential persistence and survival profiles. CF193 was detected by PCR until day 3 in light microcosms and day 6 in the dark, and by QPCR until day 14. Light significantly affected the decay rate of the CF128 marker but not the CF193 marker. Survival and persistence profiles for HF134 and HF183 markers and cells were 6 and 7 days; natural light did not significantly affect rates of human PCR marker decay, but significantly affected decay rates of human Bacteroidales cells. Conclusion: These results support use of host-specific fecal Bacteroidales markers as indicators of recent fecal pollution. The survival and persistence profiles for Bacteroidales markers are consistent with survival profiles for several fecal pathogens.