| Article ID | Journal | Published Year | Pages | File Type |
|---|---|---|---|---|
| 4481530 | Water Research | 2014 | 13 Pages |
•Propidium monoazide was used to differentiate genetic markers from live cells.•Higher sand moisture slowed the decay of both bacterial indicators and pathogens.•Total Bacteroides and MRSA have the potential to persist and increase in moist sand.•Culturable FIB and HF183 decay rates were most similar to bacterial pathogens.•The Entero1 and AllBac makers were not valid indicators of bacterial pathogens.
Beach sands impact water quality and pathogen loads, however, the comparative decay of the fecal indicator bacteria (FIB) Enterococcus spp. and Escherichia coli, and pathogens in freshwater sand have not been examined. In this study, freshwater sand microcosms were inoculated with sewage and pure cultures of bacterial pathogens to compare relative decay rates. The abundance of culturable Enterococcus spp. and E. coli, genetic markers for Enterococcus spp. (Entero1), total Bacteroides (AllBac), and human-specific Bacteroides (HF183), and genetic markers for the pathogens Campylobacter jejuni, methicillin-resistant Staphylococcus aureus (MRSA), Salmonella enterica subsp. enterica serovar Typhimurium, and Shigella flexneri were monitored over the course of two weeks using conventional culture methods and quantitative PCR (qPCR). The effect of moisture on the persistence of culturable FIB and all genetic markers was also determined. In addition, propidium monoazide (PMA) treatment was used to examine differences in the persistence of total genetic markers and those from live cells. Decay rates were statistically compared using Tukey's test. Moisture had a significant (p ≤ 0.05) effect on the decay rates of culturable indicator bacteria, total AllBac markers, and genetic markers for FIB, Salmonella, and MRSA from live cells. At 14% sand moisture, the decay rate of total markers was slower than that of live cells for all qPCR assays, but at 28% moisture, there was no difference in the decay rates of total and live markers for any assay. AllBac and MRSA markers increased in sand at 28% moisture, probably indicating cellular growth. Overall, culturable FIB and HF183 had decay rates that were most comparable to the bacterial pathogen markers examined in this study, whereas Entero1 and AllBac rarely exhibited decay rates similar to the bacterial pathogens in this study. The choice of FIB for assessment of fecal contamination in freshwater sand should take into account the pathogen of concern and sand moisture conditions.
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