Shedding of Staphylococcus aureus and methicillin-resistant Staphylococcus aureus from adult and pediatric bathers in marine waters

Abstract

BackgroundStaphylococcus 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.ResultsNasal 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.ConclusionsThis 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.

Scientific Opinion on the minimum hygiene criteria to be applied to clean seawater and on the public health risks and hygiene criteria for bottled seawater intended for domestic use

“…S. aureus (including meticillin-resistant S. aureus) has been recovered from seawater as a result of human bathing activities (Plano et al, 2011). …”

Quantification of Methicillin-Resistant Staphylococcus aureus Strains in Marine and Freshwater Samples by the Most-Probable-Number Method

“…Limitations of this method include a minimum processing time of 72 h and technical support to confirm the presence of MRSA in the Staphylococcus-positive wells. However, the current method saves time and is more specific than previously described methods (1,7,11,13,14), and, until an adequate molecular method is found that can distinguish between MRSA and mecA-positive Staphylococcus spp., is an improvement over current methods. Nevertheless, the results of the current study suggest that the Quanti-Tray 2000 MPN approach offers MRSA quantification combined with the increased detection sensitivity of broth enrichment in recreational marine and freshwater samples.…”

“…There are several potential point and non-point sources, such as recreational bathers (5,11), combined sewer overflows (2), and urban runoff (12), possibly contributing to S. aureus and MRSA loads at recreational beaches. Currently, there is no risk assessment available to provide guidance on levels of MRSA that result in human infection or colonization from contact with contaminated sand or water at marine and freshwater beaches, and more research is needed (11). A key component needed for the development of a risk assessment model is accurate quantification of MRSA from these environments.…”

“…Identified risk factors associated with community-associated MRSA outbreaks include sharing of personal care products, frequent skin-to-skin contact, skin abrasions, and crowded living conditions. Recreational marine beaches are potential reservoirs for pathogenic bacteria (1), including S. aureus and MRSA (3,5,7,11,13,14). Shedding of S. aureus and MRSA has been documented from bathers in marine waters (5,11).…”

“…Recreational marine beaches are potential reservoirs for pathogenic bacteria (1), including S. aureus and MRSA (3,5,7,11,13,14). Shedding of S. aureus and MRSA has been documented from bathers in marine waters (5,11). Contact with seawater has been associated with a 4-fold increased risk of S. aureus skin infections in children (3).…”