Quantitative evaluation of enterococci and Bacteroidales released by adults and toddlers in marine water

Traditionally, the use of enterococci has been recommended as the fecal indicator bacteria of choice for testing marine recreational water quality, and prior studies have shown that bathers shed large numbers of enterococci into the water. The current study expands upon prior research by evaluating shedding from both toddlers and adults, and by the expansion of measurements to include enterococci shedding via three different methods (membrane filter (MF), chromogenic substrate (CS), and quantitative polymerase chain reaction (qPCR)) and shedding of alternative fecal indicator bacteria (Bacteroidales human markers UCD and HF8 via qPCR). Two sets of experiments were conducted. The first experiment consisted of two groups of 10 adults who bathed together in a large pool. The second study consisted of 14 toddlers who bathed individually in a small pool which allowed for sand recovery. Sand recovery was used to estimate the amount of sand transported on the bodies of toddlers and to estimate the number of fecal indicator bacteria released from this sand. The numbers of estimated enterococci shed per adult ranged from 1.8×104 to 2.8×106 CFU, from 1.9×103 to 4.5×106 MPN, and from 3.8×105 to 5.5×106 GEU based on the MF, CS, and qPCR methods, respectively. The estimated numbers of Bacteroidales human markers ranged from 1.8×104 to 1.3×106 for UCD, and ranged from the below detection limit to 1.6×105 for HF8. The estimated amount of sand transported per toddler (n=14) into the water column after sand exposure was 8±6g on average. When normalizing the numbers of enterococci shed from toddlers via sand by the 3.9 body surface area ratio, the differences between toddlers and adults were insignificant. Contributions of sands to the total enterococci (MF) shed per toddler was 3.7±4.4% on average. Although shedding via beach sand may contribute a small fraction of the microbial load during initial bathing, it may have a significant role if bathers go to water repetitively after sand exposure

Evaluation of Conventional and Alternative Monitoring Methods for a Recreational Marine Beach with Nonpoint Source of Fecal Contamination

The objectives of this study were to compare enterococci (ENT) measurements based on the membrane filter, ENT(MF) with alternatives that can provide faster results including alternative enterococci methods (e.g. chromogenic substrate (CS), and quantitative polymerase chain reaction (qPCR)), and results from regression models based upon environmental parameters that can be measured in real-time. ENT(MF) were also compared to source tracking markers (Staphylococcus aureus, Bacteroidales human and dog markers, and Catellicoccus gull marker) in an effort to interpret the variability of the signal. Results showed that concentrations of enterococci based upon MF (< 2 to 3,320 CFU/100mL) were significantly different from the CS and qPCR methods (p < 0.01). The correlations between MF and CS (r=0.58, p<0.01) were stronger than between MF and qPCR (r≤0.36, p<0.01). Enterococci levels by MF, CS, and qPCR methods were positively correlated with turbidity and tidal height. Enterococci by MF and CS were also inversely correlated with solar radiation but enterococci by qPCR was not. The regression model based on environmental variables provided fair qualitative predictions of enterococci by MF in real-time, for daily geometric mean levels, but not for individual samples. Overall, ENT(MF) was not significantly correlated with source tracking markers with the exception of samples collected during one storm event. The inability of the regression model to predict ENT(MF) levels for individual samples is likely due to the different sources of ENT impacting the beach at any given time, making it particularly difficult to for environmental parameters to predict short-term variability of ENT(MF)

Spatial and temporal variation in indicator microbe sampling is influential in beach management decisions

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 hours 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