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Comparison of gull-specific assays targeting 16S rRNA gene of Catellicoccus marimammalium and Streptococcus spp.
Citation:
RYU, H., B. Iker, J. Pearce, J. Griffith, AND J. W. SANTO-DOMINGO. Comparison of gull-specific assays targeting 16S rRNA gene of Catellicoccus marimammalium and Streptococcus spp. . Presented at ASM 111th General Meeting, New Orleans, LA, May 21 - 24, 2011.
Impact/Purpose:
To inform the public.
Description:
Gulls have been implicated as a source of fecal contamination in inland and coastal waters. Only one gull-specific assay is currently available (i.e., gull2 qPCR assay). This assay is based on the 16S rRNA gene of Catellicocclls marimammalium and has showed a high level of host-specificity and host distribution. However, a limited number of feces and water samples have been used in test studies, and therefore further validation is needed. The primary objective of this study was to evaluate the gull2 assay against additional targeted (232) and non-targeted feces (408), and to test the occurrence of the markers in gull feces (343) and non-gull feces (762) impacted water samples collected from different geographic locations. Additionally, we compared the gull2 assay against a newly developed assay (i.e., gull3 qPCR assay) that targets Streptococcus spp. More than 80% of gull samples were positive using the gull2 assay, whereas only 22% were positive for gull3 marker. The signal intensity of the gull2 assay was higher than the gull3 assay in gull DNA extracts. Host specificity studies showed that both assays could cross react with chicken and some waterfowl, particularly pelican and Canada geese. Additionally, 27% (n=30) of pig and 53% (n=32) of goat fecal samples were positive with the gull2 and gull3 assays, respectively, although signal intensities were generally lower in non-targeted hosts. For waters not impacted with gulls, about 10% of the samples were positive, most of which were from a watershed presumed to be impacted by poultry. Of the water samples potentially impacted by gull fecal contamination, 85% and 73% were positive for the gull2 and the gull3 assays, respectively. Overall, both gull-specific assays showed a higher level of cross amplification with other avian species than non -avian hosts. This data suggests that when several waterfowl species are present in recreational waters, multiple waterfowl assays will be needed to accurately assess the contribution of each avian source. The relatively high occurrence of both gull markers in waters impacted by gull feces suggests that these assays could be used in environmental monitoring studies.