Abstract
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 4700
L during four 15
min 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 30
min 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 6×10
5 and 6×10
6 colony forming units (CFU) per person in the first 15
min 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.
