Abstract
Previous studies have used 16S rRNA gene sequences from Catellicoccus marimammalium to develop conventional PCR assays specific to gull feces. While such an assay can be used to determine the presence or absence of gull fecal pollution, it cannot estimate gull fecal loadings. The aims of this study were to adapt this assay to a Taqman real-time quantitative PCR (qPCR) format, conduct specificity and sensitivity assessments, and field-test the assay against 670 recreational water samples collected as part of the B.E.A.C.H.E.S. epidemiological study conducted by the University of Miami Oceans and Human Health Center. All of the gull samples tested in this study were positive for this qPCR assay. Out of crane, dog, duck, ibis, pelican, and human fecal samples tested, only some pelican fecal samples tested positive. This is in agreement with conventional PCR studies showing the incidence of the C. marimammalium marker in pelican and gull fecal DNA was very high (i.e 100 and 64% respectively). For the B.E.A.C.H.E.S. project, water samples were collected over a nine month period near the study bathers at a non-point-source subtropical recreational beach in Miami, Florida. When sampling days were averaged together, a seasonal effect was observed for the analyzed water samples. From January to the end of March the average number of target copies exceeded 100, with a peak of approximately 500 copies in late February. These results were also consistent with independent automated camera observations taken of the beach to enumerate the populations of people, dogs, and birds during the study. This corresponds to the general annual migration pattern of gulls through southeast Florida. Since these samples were taken during an epidemiological study, they can be further analyzed for possible associations to human health effects, including by a quantitative microbial risk assessment. The adaptations and improvements presented here for this gull-specific C. marimammalium gene marker may help us to better assess and understand the impact of gull fecal contamination on beach sand and recreational water quality.