Growth of Enterococci in Unaltered, Unseeded Beach Sands Subjected to Tidal Wetting

Abstract

Enterococci are indicator bacteria used to assess the risk of acquiring enteric disease from swimming in marine waters. Previous work identified beach sands as reservoirs of enterococci which can be transported from the sand to the sea, where they may instigate beach advisories. The present study establishes that naturally occurring enterococci can replicate in beach sands under environmentally relevant conditions. In unseeded, nonsterile microcosm experiments, it was shown that intermittent wetting of sands by seawater, like that which would occur at the high tide line, stimulates the transient replication of enterococci at rates of 0.20 to 0.63 per day (equivalent to doubling times of 1.1 to 3.5 days). Replication was not observed in control microcosms that were not subjected to wetting. Enterococci were enumerated using both culture-dependent (membrane filtration and mEI media) and culture-independent (quantitative PCR [QPCR], 23S rRNA gene based) techniques, which allowed tracking of both culturable and total enterococcus populations. Inhibition of QPCR and DNA extraction efficiencies were accounted for in the interpretation of the QPCR results. The results provide evidence that enterococci may not be an appropriate indicator of enteric disease risk at recreational beaches subject to nonpoint sources of pollution.

Occurrence of potentially human pathogenic bacteria in the seawater and in the sand of the recreational coastal beach in the southern Baltic Sea

“…This may be explained by the fact that microorganisms inhabiting the beach can survive better in the sand than in the adjacent water (Craig et al 2002). According to Yamahara et al (2009), the coastal beach sand represents more stable environment, exposed to smaller changes in physicochemical parameters than the adjacent seawater. The beach sand may be more conducive to bacteria survival and reproduction compared to seawater by reducing the solar irradiance and osmotic stress, buffering the temperature, protecting against predators and bacteriophages, lowering the concentration of inhibiting substances, increasing the availability of inorganic nutrients and organic matter and providing the surface for colonization (Craig et al 2002, Clark et al 2003, Wheeler-Alm et al 2003, Heaney et al 2009).…”

“…Swimming in the seawater and recreational activities on the sandy beach contaminated with pathogenic bacteria may cause skin, eye, ear, or nose infection, gastroenteritis, hepatitis, meningitis, salmonellosis, shigellosis, respiratory diseases, occurrence of dermatitis and mycosis (Kueh et al 1992, Efstratiou 2001, Vieira et al 2001, Esiobu et al 2004, Stewart et al 2008. Over 250 million cases of gastroenteritis, 50 million cases of respiratory diseases and 5 − 10 million cases of hepatitis are reported every year from coastal regions all over the world (Clark et al 2003, Yamahara et al 2009). …”

“…Beach water quality assessment standards based on the bathing water directive (Directive 2006/7/EC) are typically based on the number of fecal indicator bacteria such as fecal coliforms and enterococci, but it has been recognized that the presence of many pathogenic bacteria in the seawater and beach sand are not necessarily correlated with fecal indicator bacteria levels (Field & Samadpour 2007, Yamahara et al 2009). Most related studies (Yoshpe-Purer & Golderman 1987, Kueh et al 1995, Clark et al 2003, Esiobu et al 2004, Mancini et al 2005 confirm the presence of pathogenic bacteria in the seawater and in the beach sand.…”

Distribution and Differential Survival of Traditional and Alternative Indicators of Fecal Pollution at Freshwater Beaches

“…Due to their ubiquitous nature in warm-blooded animals (7)(8)(9), fecal indicators can only indicate that fecal contamination may be present; however, certain host sources are more likely than others to carry human pathogens (10). Additionally, E. coli, the most commonly used indicator in freshwater systems, has been found to survive in the environment (11)(12)(13)(14). Environmental persistence of fecal indicator bacteria undermines the utility for recreational water quality monitoring because the presence of these organisms would not necessarily indicate a recent contamination event, and in some cases, it can lead to an overestimation of the associated public health risk.…”

Genetic characterization of <i>Salmonella</i> and <i>Shigella</i> spp. isolates recovered from water and riverbed sediment of the Apies River, South Africa

“…Culturebased methods are known to seriously underestimate the bacterial pathogen counts in seawater and marine sediment (Shannon et al, 2007;Luna et al, 2010). A similar higher sensitivity of the qPCR method when compared to culturebased approaches has previously been reported in harbour sediment (Luna et al, 2012) and beach sands (Yamahara et al, 2009). These data are vital for an understanding of the potential dangers related to the presence of pathogenic bacteria in sediments.…”