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Fecal indicator microbes, such as enterococci, are often used to assess potential health risks caused by pathogens at recreational beaches. Microbe levels often vary based on collection time and sampling location. The primary goal of this study was to assess how spatial and temporal variations in sample collection, which are driven by environmental parameters, impact enterococci measurements and beach management decisions. A secondary goal was to assess whether enterococci levels can be predictive of the presence of Staphylococcus aureus, a skin pathogen. Over a ten-day period, hydrometeorologic data, hydrodynamic data, bather densities, enterococci levels, and S. aureus levels including methicillin-resistant S. aureus (MRSA) were measured in both water and sand. Samples were collected hourly for both water and sediment at knee-depth, and every 6 h for water at waist-depth, supratidal sand, intertidal sand, and waterline sand. Results showed that solar radiation, tides, and rainfall events were major environmental factors that impacted enterococci levels. S. aureus levels were associated with bathing load, but did not correlate with enterococci levels or any other measured parameters. The results imply that frequencies of advisories depend heavily upon sample collection policies due to spatial and temporal variation of enterococci levels in response to environmental parameters. Thus, sampling at different times of the day and at different depths can significantly impact beach management decisions. Additionally, the lack of correlation between S. aureus and enterococci suggests that use of fecal indicators may not accurately assess risk for some pathogens., (Copyright © 2012 Elsevier Ltd. All rights reserved.)

Background: Staphylococcus aureus including methicillin resistant S. aureus, MRSA, are human colonizing bacteria that commonly cause opportunistic infections primarily involving the skin in otherwise healthy individuals. These infections have been linked to close contact and sharing of common facilities such as locker rooms, schools and prisons Waterborne exposure and transmission routes have not been traditionally associated with S. aureus infections. Coastal marine waters and beaches used for recreation are potential locations for the combination of high numbers of people with close contact and therefore could contribute to the exposure to and infection by these organisms. The primary aim of this study was to evaluate the amount and characteristics of the shedding of methicillin sensitive S. aureus, MSSA and MRSA by human bathers in marine waters., Results: Nasal cultures were collected from bathers, and water samples were collected from two sets of pools designed to isolate and quantify MSSA and MRSA shed by adults and toddlers during exposure to marine water. A combination of selective growth media and biochemical and polymerase chain reaction analysis was used to identify and perform limited characterization of the S. aureus isolated from the water and the participants. Twelve of 15 MRSA isolates collected from the water had identical genetic characteristics as the organisms isolated from the participants exposed to that water while the remaining 3 MRSA were without matching nasal isolates from participants. The amount of S. aureus shed per person corresponded to 105 to 106 CFU per person per 15-minute bathing period, with 15 to 20% of this quantity testing positive for MRSA., Conclusions: This is the first report of a comparison of human colonizing organisms with bacteria from human exposed marine water attempting to confirm that participants shed their own colonizing MSSA and MRSA into their bathing milieu. These findings clearly demonstrate that adults and toddlers shed their colonizing organisms into marine waters and therefore can be sources of potentially pathogenic S. aureus and MRSA in recreational marine waters. Additional research is needed to evaluate recreational beaches and marine waters as potential exposure and transmission pathways for MRSA.

Enterococci, a common fecal indicator, and Staphylococcus aureus, a common skin pathogen, can be shed by bathers affecting the quality of recreational waters and resulting in possible human health impacts. Due to limited information available concerning human shedding of these microbes, this study focused on estimating the amounts of enterococci and S. aureus shed by bathers directly off their skin and indirectly via sand adhered to skin. Two sets of experiments were conducted at a marine beach located in Miami-Dade County, Florida. The first study, referred to as the "large pool" study, involved 10 volunteers who immersed their bodies in 4700L during four 15min cycles with exposure to beach sand in cycles 3 and 4. The "small pool" study involved 10 volunteers who were exposed to beach sand for 30min before they individually entered a small tub. After each individual was rinsed with off-shore marine water, sand and rinse water were collected and analyzed for enterococci. Results from the "large pool" study showed that bathers shed concentrations of enterococci and S. aureus on the order of 6x10(5) and 6x10(6) colony forming units (CFU) per person in the first 15min exposure period, respectively. Significant reductions in the bacteria shed per bather (50% reductions for S. aureus and 40% for enterococci) were observed in the subsequent bathing cycles. The "small pool" study results indicated that the enterococci contribution from sand adhered to skin was small (about 2% of the total) in comparison with the amount shed directly from the bodies of the volunteers. Results indicated that bathers transport significant amounts of enterococci and S. aureus to the water column, and thus human microbial bathing load should be considered as a non-point source when designing recreational water quality models.