BEACHNET==> New article on enterococcal surface protein (esp)

[Meredith Nevers <mnevers@usgs.gov>]

Environmental Occurrence of the Enterococcal
Surface Protein (esp) Gene is an Unreliable Indicator of Human Fecal
Contamination


Muruleedhara N. Byappanahalli*,
Katarzyna Przybyla-Kelly, Dawn A. Shively and Richard L. Whitman
U.S. Geological Survey, Great Lakes Science
Center, Lake Michigan Ecological Research Station, 1100 Mineral Springs
Road, Porter, Indiana 46304
Environ. Sci. Technol., 2008, 42 (21),
pp 8014–8020
DOI: 10.1021/es800481p
Publication Date (Web): October 3, 2008
Copyright © 2008 American Chemical Society

* Corresponding author phone: (219) 926-8336;
fax: (219) 929-5792; e-mail: byappan@usgs.gov.
Abstract

The enterococcal surface protein (esp) gene found in Enterococcus faecalis and E. faecium has recently been explored as a marker of sewage pollution in recreational waters but its occurrence and distribution in environmental enterococci has not been well-documented. If the esp gene is found in environmental samples, there are potential implications for microbial source tracking applications. In the current study, a total of 452 samples (lake water, 100; stream water, 129; nearshore sand, 96; and backshore sand, 71; Cladophora sp. (Chlorophyta), 41; and periphyton (mostly Bacillariophyceae), 15) collected from the coastal watersheds of southern Lake Michigan were selectively cultured for enterococci and then analyzed for the esp gene by PCR, targeting E. faecalis/E. faecium (esp_fs/fm) and E. faecium (esp_fm). Overall relative frequencies for esp_fs/fm and esp_fm were 27.4 and 5.1%. Respective percent frequency for the esp_fs/fm and esp_fm was 36 and 14% in lake water; 38.8 and 2.3% in stream water; 24 and 6.3% in nearshore sand; 0% in backshore sand; 24.4 and 0% in Cladophora sp.; and 33.3 and 0% in periphyton. The overall occurrence of both esp_fs/fm and esp_fm was significantly related (χ² = 49, P < 0.0001). Post-rain incidence of esp_fs/fm increased in lake and stream water and nearshore sand. Further, E. coli and enterococci cell densities were significant predictors for esp_fs/fm occurrence in post-rain lake water, but esp_fm was not. F⁺ coliphage densities were not significant predictors for esp_fm or esp_fs/fm gene incidence. In summary, the differential occurrence of the esp gene in the environment suggests that it is not limited to human fecal sources and thus may weaken its use as a reliable tool in discriminating contaminant sources (i.e., human vs nonhuman).






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Meredith B. Nevers
Research Ecologist
USGS, Lake Michigan Ecological Research Station
1100 N. Mineral Springs Rd., Porter, IN 46304
phone (219) 926-8336  ext. 425   fax (219) 929-5792
mnevers@usgs.gov
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