Physicochemical Factors Influence the Abundance and Culturability of Human Enteric Pathogens and Fecal Indicator Organisms in Estuarine Water and Sediment

Abstract

To assess fecal pollution in coastal waters, current monitoring is reliant on culture-based enumeration of bacterial indicators, which does not account for the presence of viable but non-culturable or sediment-associated micro-organisms, preventing effective quantitative microbial risk assessment (QMRA). Seasonal variability in viable but non-culturable or sediment-associated bacteria challenge the use of fecal indicator organisms (FIOs) for water monitoring. We evaluated seasonal changes in FIOs and human enteric pathogen abundance in water and sediments from the Ribble and Conwy estuaries in the UK. Sediments possessed greater bacterial abundance than the overlying water column, however, key pathogenic species (Shigella spp., Campylobacter jejuni, Salmonella spp., hepatitis A virus, hepatitis E virus and norovirus GI and GII) were not detected in sediments. Salmonella was detected in low levels in the Conwy water in spring/summer and norovirus GII was detected in the Ribble water in winter. The abundance of E. coli and Enterococcus spp. quantified by culture-based methods, rarely matched the abundance of these species when measured by qPCR. The discrepancy between these methods was greatest in winter at both estuaries, due to low CFU's, coupled with higher gene copies (GC). Temperature accounted for 60% the variability in bacterial abundance in water in autumn, whilst in winter salinity explained 15% of the variance. Relationships between bacterial indicators/pathogens and physicochemical variables were inconsistent in sediments, no single indicator adequately described occurrence of all bacterial indicators/pathogens. However, important variables included grain size, porosity, clay content and concentrations of Zn, K, and Al. Sediments with greater organic matter content and lower porosity harbored a greater proportion of non-culturable bacteria (including dead cells and extracellular DNA) in winter. Here, we show the link between physicochemical variables and season which govern culturability of human enteric pathogens and FIOs. Therefore, knowledge of these factors is critical for accurate microbial risk assessment. Future water quality management strategies could be improved through monitoring sediment-associated bacteria and non-culturable bacteria. This could facilitate source apportionment of human enteric pathogens and FIOs and direct remedial action to improve water quality.

Assessment of bacterial pathogens on edible macroalgae in coastal waters

“…These findings indicate that Vibrio contamination during the winter-spring kelp growing season is possible and should not be overlooked due to low environmental temperatures. However, PCR methods may detect pathogens in a viable but non-culturable (VBNC) state due to low environmental temperature (Hassard et al 2017). Bacteria in VBNC are expected to maintain virulence and be pathogenic upon resuscitation (Oliver 2005) or in the case of macroalgal aquaculture, processing, and should therefore still be considered in food safety risk assessments.…”

Antibiotic Resistance of Enterobacteria present in an Urban Wastewater Treatment Plants: A Public Health Problem

“…1.5x10 6 1.9x10 6 --3.5x10 6 3.0x10 6 --9 2.0x10 7 2.4x10 7 --8.0x10 6 7.4x10 6 4.0x10 6 4.3x10 6 10 1.0x10 3 1.6x10 3 --5.2x10 6 5.9x10 6 1.1x10 3 1.0x10 3 11 1.8x10 3 1.3x10 3 --3.2x10 4 2.9x10 4 1.1x10 2 1.0x10 2 12 2.4x10 3 2.8x10 3 --2.5x10 5 2.8x10 5 1.0x10 2 -13 3.1x10 3 2.7x10 3 --1.5x10 3 1.1x10 5 1.0x10 2 1.1x10 2 14 -->300 >300 ----15 -->300 >300 ----16 -->300 >300 ----17 -->300 >300 ----1: EMB agar-(absence of colonies) 2: MacConkey agar In this case, E. coli is the most abundant bacterium with a growth average of 7.7x10 6 CFU/g. Studies carry out by [23], in which analyzes the quantity of Enterobacteria present in waste water treatment plants of milk industry, show that the most abundant bacterium is also E. coli, with an average of 2.6x10 7 CFU/g.…”

“…Frequently, the dispersion of human enteric bacteria occurs through raw sewage are often discharged into low-temperature marine and aquatic environments, raising the question of whether human enteric pathogens (i.e., Salmonella) and indicator organisms (i.e., E. coli) can adapt and persist in these extreme environments. Genomes of these bacteria have more than 1,000 genes, whose functions remain unknown and which could contribute to proliferation in non-host environments, such as soil and water, even in the sludge from the treatment plants, the presence of CFU of Enterobacteria that survive the depurative processes is reported, consequently, they promote the transmission to a new host and the resistance or the prevalence of infectious diseases by resistance [4].…”

Factors affecting the spatial and temporal distribution of E. coli in intertidal estuarine sediments

“…Sediments act as a reservoir for faecal bacteria, with freshwater and marine sediments observed to contain much higher densities of faecal bacteria than the overlying water (Davies et al, 1995;Hassard et al, 2017). Numbers of faecal bacteria can increase several-fold when associated with suspended particulates as compared to free-floating in surrounding waters (Droppo et al, 2009).…”

“…Whilst performing a full suite of sediment analyses is impractical for monitoring by regulatory bodies, the ability to pre-emptively identify areas and time periods of potentially high loading of FIOs using a limited number of easily accessible measurements will greatly facilitate risk management. A wide range of climatic, physical, chemical and biological variables relevant to both the sediment and interstitial water are known to affect the abundance and survival of faecal bacteria in estuarine sediments (Pachepsky and Shelton, 2011;Perkins et al, 2014;Hassard et al, 2016;Hassard et al, 2017;Schang et al, 2018). Many properties of intertidal sediments co-vary (Dale, 1974;Mayer et al, 1985;Flemming and Delafontaine, 2000;Paterson et al, 2000;Venkatramanan et al, 2011), for example, sediments with smaller particle sizes often having increased organic matter and nutrient content.…”