Differentiation of Fecal Escherichia coli from Human, Livestock, and Poultry Sources by rep-PCR DNA Fingerprinting on the Shellfish Culture Area of East China Sea

Genotypic diversity in multi-drug-resistant E. coli isolated from animal feces and Yamuna River water, India, using rep-PCR fingerprinting

Genotypic diversity among multi-drug-resistant (MDR) aquatic E. coli isolated from different sites of Yamuna River was analyzed using repetitive element PCR (rep-PCR) methods viz. ERIC-PCR and (GTG)₅-PCR and compared with the MDR animal fecal isolates. The 97 E. coli isolates belonging to different serotypes, phylogroups, and multi-drug resistance patterns were analyzed. High genetic diversity was observed by both the methods; however, (GTG)₅ typing showed higher discriminating potential. Combination of ERIC types (E1-E32) and (GTG)₅ types (G1-G46) generated 77 genotypes. The frequency of genotypes ranged from 0.013 to 0.065. The genotype composition of E. coli isolates was highly diverse at all the sampling sites across Yamuna River except at its entry site in Delhi. The sampling sites under the influence of high anthropogenic activities showed an increase in number of unique genotype isolates. These sites also exhibited high multiple antibiotic resistance (MAR) indexes (above 0.25) suggesting high risk of contamination. Principal coordinate analysis (PCoA) showed limited clustering of genotypes based on the sampling sites. The most frequent genotypes were grouped in the positive zone of both the principal coordinates (PC1 and PC2). The genotypes of most of the animal fecal isolates were unique and occupied a common space in the negative PC1 area forming a separate cluster. High genotypic diversity among the aquatic E. coli and the drain isolates, discharging the untreated municipal waste in the river, was observed, suggesting that the sewage effluents contribute substantially to contamination of this river system than animal feces. The presence of such a high diversity among the MDR E. coli isolates in the natural river systems is of great public health significance and highlights the need of an efficient surveillance system for better management of Indian natural water bodies.

Management Scale Assessment of Practices to Mitigate Cattle Microbial Water Quality Impairments of Coastal Waters

Coastal areas support multiple important resource uses including recreation, aquaculture, and agriculture. Unmanaged cattle access to stream corridors in grazed coastal watersheds can contaminate surface waters with fecal-derived microbial pollutants, posing risk to human health via activities such as swimming and shellfish consumption. Improved managerial control of cattle access to streams through implementation of grazing best management practices (BMPs) is a critical step in mitigating waterborne microbial pollution in grazed watersheds. This paper reports trend analysis of a 19-year dataset to assess long-term microbial water quality responses resulting from a program to implement 40 grazing BMPs within the Olema Creek Watershed, a primary tributary to Tomales Bay, USA. Stream corridor grazing BMPs implemented included: (1) Stream corridor fencing to eliminate/control cattle access, (2) hardened stream crossings for cattle movements across stream corridors, and (3) off stream drinking water systems for cattle. We found a statistically significant reduction in fecal coliform concentrations following the initial period of BMP implementation, with overall mean reductions exceeding 95% (1.28 log10)—consistent with 1—2 log10 (90–99%) reductions reported in other studies. Our results demonstrate the importance of prioritization of pollutant sources at the watershed scale to target BMP implementation for rapid water quality improvements and return on investment. Our findings support investments in grazing BMP implementation as an important component of policies and strategies to protect public health in grazed coastal watersheds.

Genetic diversity of Escherichia coli isolates from surface water and groundwater in a rural environment

The genetic characteristics among Escherichia coli strains can be grouped by origin of isolation. Then, it is possible to use the genotypes as a tool to determine the source of water contamination. The aim of this study was to define water aptitude for human consumption in a rural basin and to assess the diversity of E. coli water populations. Thus, it was possible to identify the main sources of fecal contamination and to explore linkages with the hydrogeological environment and land uses. The bacteriological analysis showed that more than 50% of samples were unfit for human consumption. DNA fingerprinting analysis by BOX-PCR indicated low genotypic diversity of E. coli isolates taken from surface water and groundwater. The results suggested the presence of a dominant source of fecal contamination. The relationship between low genotypic diversity and land use would prove that water contamination comes from livestock. The genetic diversity of E. coli isolated from surface water was less than that identified in groundwater because of the different hydraulic features of both environments. Furthermore, each one of the two big strain groups identified in this basin is located in different sub-basins, showing that hydrological dynamics exerts selective pressure on bacteria DNA.

E. coli Surface Properties Differ between Stream Water and Sediment Environments

The importance of E. coli as an indicator organism in fresh water has led to numerous studies focusing on cell properties and transport behavior. However, previous studies have been unable to assess if differences in E. coli cell surface properties and genomic variation are associated with different environmental habitats. In this study, we investigated the variation in characteristics of E. coli obtained from stream water and stream bottom sediments. Cell properties were measured for 77 genomically different E. coli strains (44 strains isolated from sediments and 33 strains isolated from water) under common stream conditions in the Upper Midwestern United States: pH 8.0, ionic strength 10 mM and 22°C. Measured cell properties include hydrophobicity, zeta potential, net charge, total acidity, and extracellular polymeric substance (EPS) composition. Our results indicate that stream sediment E. coli had significantly greater hydrophobicity, greater EPS protein content and EPS sugar content, less negative net charge, and higher point of zero charge than stream water E. coli. A significant positive correlation was observed between hydrophobicity and EPS protein for stream sediment E. coli but not for stream water E. coli. Additionally, E. coli surviving in the same habitat tended to have significantly larger (GTG)₅ genome similarity. After accounting for the intrinsic impact from the genome, environmental habitat was determined to be a factor influencing some cell surface properties, such as hydrophobicity. The diversity of cell properties and its resulting impact on particle interactions should be considered for environmental fate and transport modeling of aquatic indicator organisms such as E. coli.

Application of Faecalibacterium 16S rDNA genetic marker for accurate identification of duck faeces

The aim of this study was to judge the legal duty of pollution liabilities by assessing a duck faeces-specific marker, which can exclude distractions of residual bacteria from earlier contamination accidents. With the gene sequencing technology and bioinformatics method, we completed the comparative analysis of Faecalibacterium sequences, which were associated with ducks and other animal species, and found the sequences unique to duck faeces. Polymerase chain reaction (PCR) and agarose gel electrophoresis techniques were used to verify the reliability of both human and duck faeces-specific primers. The duck faeces-specific primers generated an amplicon of 141 bp from 43.3 % of duck faecal samples, 0 % of control samples and 100 % of sewage wastewater samples that contained duck faeces. We present here the initial evidence of Faecalibacterium-based applicability as human faeces-specificity in China. Meanwhile, this study represents the initial report of a Faecalibacterium marker for duck faeces and suggests an independent or supplementary environmental biotechnology of microbial source tracking (MST).

Differential utility of the Bacteroidales DNA and RNA markers in the tiered approach for microbial source tracking in subtropical seawater

Source tracking of fecal pollution is an emerging component in water quality monitoring. It may be implemented in a tiered approach involving Escherichia coli and/or Enterococcus spp. as the standard fecal indicator bacteria (FIB) and the 16S rRNA gene markers of Bacteroidales as source identifiers. The relative population dynamics of the source identifiers and the FIB may strongly influence the implementation of such approach. Currently, the relative performance of DNA and RNA as detection targets of Bacteroidales markers in the tiered approach is not known. We compared the decay of the DNA and RNA of the total (AllBac) and ruminant specific (CF128) Bacteroidales markers with those of the FIB in seawater spiked with cattle feces. Four treatments of light and oxygen availability simulating the subtropical seawater of Hong Kong were tested. All Bacteroidales markers decayed significantly slower than the FIB in all treatments. Nonetheless, the concentrations of the DNA and RNA markers and E. coli correlated significantly in normoxic seawater independent of light availability, and in hypoxic seawater only under light. In hypoxic seawater without light, the concentrations of RNA but not DNA markers correlated with that of E. coli. Generally, the correlations between Enterococcus spp. and Bacteroidales were insignificant. These results suggest that either DNA or RNA markers may complement E. coli in the tiered approach for normoxic or hypoxic seawater under light. When light is absent, either DNA or RNA markers may serve for normoxic seawater, but only the RNA markers are suitable for hypoxic seawater.

Gulls identified as major source of fecal pollution in coastal waters: a microbial source tracking study

Gulls were reported as sources of fecal pollution in coastal environments and potential vectors of human infections. Microbial source tracking (MST) methods were rarely tested to identify this pollution origin. This study was conducted to ascertain the source of water fecal contamination in the Berlenga Island, Portugal. A total of 169 Escherichia coli isolates from human sewage, 423 isolates from gull feces and 334 water isolates were analyzed by BOX-PCR. An average correct classification of 79.3% was achieved. When an 85% similarity cutoff was applied 24% of water isolates were present in gull feces against 2.7% detected in sewage. Jackknifing resulted in 29.3% of water isolates classified as gull, and 10.8% classified as human. Results indicate that gulls constitute a major source of water contamination in the Berlenga Island. This study validated a methodology to differentiate human and gull fecal pollution sources in a real case of a contaminated beach.

Utilisation of Rep-PCR to track microbes in aerosols collected adjacent to their source, a saline lake in Victoria, Australia

Dust storms are a major source of aerosolized bacteria, especially in the drought conditions experienced in Australia in the decade to 2009. The major aims of this project were to identify the culturable bacteria in environmental samples and to genetically fingerprint all isolates using repetitive element PCR (Rep-PCR) to investigate the possibility of tracking isolates from their source into the atmosphere. Four field trips were conducted to a dry lake in western Victoria, Australia to sample aerosols and sediments. Aerosols were collected at heights up to 150 m using vacuum pumps with filters attached to a tethered helium balloon, while corresponding sediments were collected in sterile polypropylene tubes. Isolates were cultivated on Tryptic Soy Agar, R2 Agar and Marine Agar, and grown in dark conditions at ambient temperature. By sequencing the 16S rRNA gene of 270 isolates, fifteen different bacterial families were identified, with both the aerosols and sediments dominated by the Bacillaceae family. Four sets of Rep-PCR primers were tested, with the ERIC and (GTG)5 primers proving to be the most suitable for fingerprinting the cultured taxa. Rep-PCR revealed very high strain diversity in the samples collected, however some strains were still able to be tracked from sediments up to 150 m in height. This shows the potential of Rep-PCR, however very large reference databases would be required for the technique to be more useful.