Monitoring urban beaches with qPCR vs. culture measures of fecal indicator bacteria: Implications for public notification

Abstract

BackgroundThe United States Environmental Protection Agency has established methods for testing beach water using the rapid quantitative polymerase chain reaction (qPCR) method, as well as “beach action values” so that the results of such testing can be used to make same-day beach management decisions. Despite its numerous advantages over culture-based monitoring approaches, qPCR monitoring has yet to become widely used in the US or elsewhere. Considering qPCR results obtained on a given day as the best available measure of that day’s water quality, we evaluated the frequency of correct vs. incorrect beach management decisions that are driven by culture testing.MethodsBeaches in Chicago, USA, were monitored using E. coli culture and enterococci qPCR methods over 894 beach-days in the summers of 2015 and 2016. Agreement in beach management using the two methods, after taking into account agreement due to chance, was summarized using Cohen’s kappa statistic.ResultsNo meaningful agreement (beyond that expected by chance) was observed between beach management actions driven by the two pieces of information available to beach managers on a given day: enterococci qPCR results ofsamples collected that morning and E. coli culture results of samples collected the previous day. The E. coli culture beach action value was exceeded 3.4 times more frequently than the enterococci qPCR beach action value (22.6 vs. 6.6% of beach-days).ConclusionsThe largest evaluation of qPCR-based beach monitoring to date provides little scientific rationale for continued E. coli culture testing of beach water in our setting. The observation that the E. coli culture beach action value was exceeded three times as frequently as the enterococci qPCR beach action value suggests that, although the beach action values for bacteria using different measurement methods are thought to provide comparable information about health risk, this does not appear to be the case in all settings.

The Impact of Tides on Microbial Water Quality at an Inland River Beach

“…Since its approval by the USEPA in the latest recreational water quality criteria (USEPA, 2012b), the inclusion of qPCR for enterococci detection in routine monitoring is being considered in several states as a rapid method (Dorevitch et al, 2017; Haugland et al, 2014; Kinzelman et al, 2013; USEPA, 2014). The major difference between USEPA Method 1600 and Method 1611 is that the culture‐based method detects only viable enterococci, whereas the qPCR method detects the enterococci DNA within the viable cells, dead cells, or free‐floating DNA (Walters et al, 2009) and also detects the variability in the target enterococcus species (Moore et al, 2008; Ryu et al, 2013).…”

The disparity between regulatory measurements of E. coli in public bathing waters and the public expectation of bathing water quality

“…The transfer of existing molecular biological tools, such as qPCR, is therefore gaining momentum largely because these methods permit a much more rapid sample processing time (1 -2 hours). Thus, molecular biological tools offer an opportunity to provide a more meaningful statement of microbial risk to water users by providing near-real-time information, and thus enable more informed decisionmaking for water-based activities (Dorevitch et al, 2017). However, our study has suggested that the majority of beach-users don't engage with information on bathing water quality, and so the value of an increase in the speed of reporting microbial water quality to a typical beach-user is limited.…”

Solar Powered Microplasma-Generated Ozone: Assessment of a Novel Point-of-Use Drinking Water Treatment Method

“…The E. coli culture method with chromogenic substrate is considered by the USEPA to be comparable to membrane filtration for a variety of regulatory purposes [22]. The enterococci quantitative polymerase chain reaction (qPCR) method is used for beach water monitoring, as we have previously described [23]. The simplified rapid coliphage method (EasyPhage, Scientific Methods, Inc., Granger, IN, USA) was compared to EPA Method 1602 using seven serial dilutions of MS2 phage (obtained from Scientific Methods, Inc., Granger, IN, USA).…”