Characterization and Isolation of Fecal Indicator Bacteria, Staphylococcus aureus, and Methicillin-resistant Staphylococcus aureus from Pacific Northwest Marine Beach Samples

Abstract

University of Washington Abstract Characterization and Isolation of Fecal Indicator Bacteria, Staphylococcus aureus, and Methicillin-resistant Staphylococcus aureus from Pacific Northwest Marine Beach Samples Shonnessy Gilmore Chair of the Supervisory Committee: Professor Marilyn Roberts Environmental and Occupational Health Sciences The aims of this study were to quantify fecal indicator bacteria (FIB) and Staphylococcus spp. in algal wrack and freshwater streams at twelve Washington State marine beaches, and to isolate Staphylococcus aureus, methicillin-resistant Staphylococcus aureus (MRSA), and vancomycin-resistant Enterococci (VRE) from algal wrack (n=93), freshwater streams traversing marine beaches (n=13), and seabird feces (n=63) found on public marine recreational beaches. Samples were collected from May through November 2011. Algal wrack and freshwater stream samples were processed using IDEXXTM Most Probable Number (MPN) method to quantify Enterococcus spp., coliforms, E. coli, and a modified method for Staphylococcus spp. Algae wrack, freshwater, and bird feces were enriched and isolated for Staphylococcus aureus and methicillin-resistant Staphylococcus aureus. Isolates were biochemically verified as MRSA and typed by SCCmec typing. Of the 92 Staphylococcus-enrichment wrack samples, 15 [16.3%] were methicillin-susceptible S. aureus [MSSA], and 1 [1.1%] sample was MRSA positive. From 13 freshwater samples enriched for Staphylococcus, 4 [31%] were MSSA, and 1 [7.7%] sample was MRSA positive. Of the 64 bird feces samples, 2 [3.1%] samples were positive for MSSA, and 3 [4.7%] were MRSA positive. Of the 5 MRSA characterized, 1 (20%) was SCCmec type IV, one (20%) type II, and three (60%) non-typeable. No VRE was isolated. FIB was found at all beaches sampled for wrack and freshwater. This study extends our knowledge of the types of microbes distributed throughout recreational beach environments. Further quantitative microbial risk assessment is needed to determine potential effects on human health.