Indicator microbes correlate with pathogenic bacteria, yeasts and helminthes in sand at a subtropical recreational beach site

Aims: Research into the relationship between pathogens, faecal indicator microbesand environmental factors in beach sand has been limited, yet vital to the understanding of the microbial relationship between sand and the water column and to the improvement of criteria for better human health protection at beaches. The objectives of this study were to evaluate the presence and distribution of pathogensin various zones of beach sand (subtidal, intertidal and supratidal) and to assess their relationship with environmental parameters and indicator microbesat a non- point source subtropicalmarine beach. Methods and Results: In this exploratory study in subtropical Miami(Florida, USA), beach sand samples were collected and analysed over the course of 6 days for several pathogens, microbial source trackingmarkers and indicator microbes. An inverse correlation between moisture content and most indicator microbeswas found. Significant associations were identified between some indicator microbesand pathogens(such as nematode larvae and yeasts in the genus Candida), which are from classes of microbesthat are rarely evaluated in the context of recreational beach use. Conclusions: Results indicate that indicator microbesmay predict the presence of some of the pathogens, in particular helminthes, yeasts and the bacterial pathogenStaphylococcus aureus including methicillin-resistant forms. Indicator microbesmay thus be useful for monitoring beach sand and water quality at non- point sourcebeaches. Significance and Impact of the Study: The presence of both indicator microbesand pathogensin beach sand provides one possible explanation for human health effects reported at non- point sourcesbeaches.