Epidemic Escherichia coli ST131 and Enterococcus faecium ST17 in coastal marine sediments from an Italian beach

Examining the potential impacts of a coastal renourishment project on the presence and abundance of Escherichia coli

Erosion poses a significant threat to oceanic beaches worldwide. To combat this threat, management agencies often utilize renourishment, which supplements eroded beaches with offsite sand. This process can alter the physical characteristics of the beach and can influence the presence and abundance of microbial communities. In this study, we examined how an oceanic beach renourishment project may have impacted the presence and abundance of Escherichia coli (E. coli), a common bacteria species, and sand grain size, a sediment characteristic that can influence bacterial persistence. Using an observational field approach, we quantified the presence and abundance of E. coli in sand (from sub-tidal, intertidal, and dune zones on the beach) and water samples at study sites in both renourished and non-renourished sections of Folly Beach, South Carolina, USA in 2014 and 2015. In addition, we also measured how renourishment may have impacted sand grain size by quantifying the relative frequency of grain sizes (from sub-tidal, intertidal, and dune zones on the beach) at both renourished and non-renourished sites. Using this approach, we found that E. coli was present in sand samples in all zones of the beach and at each of our study sites in both years of sampling but never in water samples. Additionally, we found that in comparison to non-renourished sections, renourished sites had significantly higher abundances of E. coli and coarser sand grains in the intertidal zone, which is where renourished sand is typically placed. However, these differences were only present in 2014 and were not detected when we resampled the study sites in 2015. Collectively, our findings show that E. coli can be commonly found in this sandy beach microbial community. In addition, our results suggest that renourishment has the potential to alter both the physical structure of the beach and the microbial community but that these impacts may be short-lived.

Multidrug-resistant Enterococcus faecium strains enter the Norwegian marine environment through treated sewage

This study aimed to understand the antibiotic resistance prevalence among Enterococcus spp. from raw and treated sewage in Bergen city, Norway. In total, 517 Enterococcus spp. isolates were obtained from raw and treated sewage from five sewage treatment plants (STPs) over three sampling occasions, with Enterococcus faecium as the most prevalent (n = 492) species. E. faecium strains (n = 307) obtained from the influent samples, showed the highest resistance against quinupristin/dalfopristin (67.8%). We observed reduced susceptibility to erythromycin (30.6%) and tetracycline (6.2%) in these strains. E. faecium strains (n = 185) obtained from the effluent samples showed highest resistance against quinupristin/dalfopristin (68.1%) and reduced susceptibility to erythromycin (24.9%) and tetracycline (8.6%). We did not detect resistance against last-resort antibiotics, such as linezolid, vancomycin, and tigecycline in any of the strains. Multidrug-resistant (MDR) E. faecium strains were detected in both influent (2.3%) and effluent (2.2%) samples. Whole genome sequencing of the Enterococcus spp. strains (n = 25) showed the presence of several antibiotic resistance genes, conferring resistance against aminoglycosides, tetracyclines, and macrolides, as well as several virulence genes and plasmid replicons. Two sequenced MDR strains from the effluents belonged to the hospital-associated clonal complex 17 and carried multiple virulence genes. Our study demonstrates that clinically relevant MDR Enterococcus spp. strains are entering the marine environment through treated sewage.

Genetic analysis of vancomycin-variable Enterococcus faecium clinical isolates in Italy

PURPOSE

To investigate the occurrence of vancomycin-variable enterococci (VVE) in a hospital in central Italy.

METHODS

vanA positive but vancomycin-susceptible Enterococcus faecium isolates (VVE-S) were characterized by antibiotic susceptibility tests, molecular typing (PFGE and MLST), and WGS approach. The reversion of VVE-S to a resistant phenotype was assessed by exposure to increasing vancomycin concentrations, and the revertant isolates were used in filter mating experiments. qPCR was used to analyze the plasmid copy number.

RESULTS

Eleven putative VVE-S were selected. WGS revealed two categories of vanA cluster plasmid located: the first type showed the lack of vanR, the deletion of vanS, and an intact vanH/vanA/vanX cluster; the second type was devoid of both vanR and vanS and showed a deletion of 544-bp at the 5'-end of the vanH. Strains (n = 7) carrying the first type of vanA cluster were considered VVE-S and were able to regain a resistance phenotype (VVE-R) in the presence of vancomycin, due to a 44-bp deletion in the promoter region of vanH/vanA/vanX, causing its constitutive expression. VVE-R strains were not able to transfer resistance by conjugation, and the resistance phenotype was unstable: after 11 days of growth without selective pressure, the revertants were still resistant but showed a lower vancomycin MIC. A higher plasmid copy number in the revertant strains was probably related to the resistance phenotype.

CONCLUSION

We highlight the importance of VVE transition to VRE under vancomycin therapy resulting in a potential failure treatment. We also report the first-time identification of VVE-S isolates pstS-null belonging to ST1478.

Microbiological and Toxicological Investigations on Bivalve Molluscs Farmed in Sicily

Bivalves can concentrate biological and chemical pollutants, causing foodborne outbreaks whose occurrence is increasing, due to climatic and anthropic factors that are difficult to reverse, hence the need for improved surveillance. This study aimed to evaluate the hygienic qualities of bivalves sampled along the production and distribution chain in Sicily and collect useful data for consumer safety. Bacteriological and molecular analyses were performed on 254 samples of bivalves for the detection of enteropathogenic Vibrio, Arcobacter spp., Aeromonas spp., Salmonella spp., and beta-glucuronidase-positive Escherichia coli. A total of 96 out of 254 samples, collected in the production areas, were processed for algal biotoxins and heavy metals detection. Bacterial and algal contaminations were also assessed for 21 samples of water from aquaculture implants. Vibrio spp., Arcobacter spp., Aeromonas hydrophila, Salmonella spp., and Escherichia coli were detected in 106/254, 79/254, 12/254, 16/254, and 95/254 molluscs, respectively. A total of 10/96 bivalves tested positive for algal biotoxins, and metals were under the legal limit. V. alginolyticus, A. butzleri, and E. coli were detected in 5, 3, and 3 water samples, respectively. Alexandrium minutum, Dinophysis acuminata, Lingulodinium polyedra, and Pseudonitzschia spp. were detected in water samples collected with the biotoxin-containing molluscs. Traces of yessotoxins were detected in molluscs from water samples containing the corresponding producing algae. Despite the strict regulation by the European Commission over shellfish supply chain monitoring, our analyses highlighted the need for efficiency improvement.

Enhanced detection of viruses for improved water safety

Human viruses pose a significant health risk in freshwater environments, but current monitoring methods are inadequate for detecting viral presence efficiently. We evaluated a novel passive in-situ concentration method using granular activated carbon (GAC). This study detected and quantified eight enteric and non-enteric, pathogenic viruses in a freshwater recreational lake in paired grab and GAC passive samples. The results found that GAC passive sampling had a higher detection rate for all viruses compared to grab samples, with adenovirus found to be the most prevalent virus, followed by respiratory syncytial virus, norovirus, enterovirus, influenza A, SARS-CoV-2, and rotavirus. GAC in-situ concentration allowed for the capture and recovery of viral gene copy targets that ranged from one to three orders of magnitude higher than conventional ex-situ concentration methods used in viral monitoring. This simple and affordable sampling method may have far-reaching implications for reducing barriers associated with viral monitoring across various environmental contexts.

Integrating culture-based and molecular methods provides an improved assessment of microbial quality in a coastal lagoon

Faecal pollution in aquatic environments is a worldwide public health concern, yet the reliability and comprehensiveness of the methods used to assess faecal contamination are still debated. We compared three approaches, namely a culture-based method to enumerate Faecal Indicator Bacteria (FIB), a FIB-targeting qPCR assay, and High-Throughput Sequencing (HTS) to detect faeces- and sewage-associated taxa in water and sediment samples of an impacted model lagoon and its adjacent sea across one year. Despite at different levels, all approaches agreed in showing a higher contamination in the lagoon than in the sea, and higher in sediments than water. FIB significantly correlated when considering separately sediment and water, and when using both cultivation and qPCR. Similarly, FIB correlated between cultivation and qPCR, but qPCR provided consistently higher estimates of FIB. Faeces-associated bacteria positively correlated with cultivated FIB in both compartments, whereas sewage-associated bacteria did only in water. Considering their benefits and limitations, we conclude that, in our study site, improved quali-quantitative information on contamination is provided when at least two approaches are combined (e.g., cultivation and qPCR or HTS data). Our results provide insights to move beyond the use of FIB to improve faecal pollution management in aquatic environments and to incorporate HTS analysis into routine monitoring.

Degradation potential of alkanes by diverse oil-degrading bacteria from deep-sea sediments of Haima cold seep areas, South China Sea

Marine oil spills are a significant concern worldwide, destroying the ecological environment and threatening the survival of marine life. Various oil-degrading bacteria have been widely reported in marine environments in response to marine oil pollution. However, little information is known about culturable oil-degrading bacteria in cold seep of the deep-sea environments, which are rich in hydrocarbons. This study enriched five oil-degrading consortia from sediments collected from the Haima cold seep areas of the South China Sea. Parvibaculum, Erythrobacter, Acinetobacter, Alcanivorax, Pseudomonas, Marinobacter, Halomonas, and Idiomarina were the dominant genera. Further results of bacterial growth and degradation ability tests indicated seven efficient alkane-degrading bacteria belonging to Acinetobacter, Alcanivorax, Kangiella, Limimaricola, Marinobacter, Flavobacterium, and Paracoccus, whose degradation rates were higher in crude oil (70.3–78.0%) than that in diesel oil (62.7–66.3%). From the view of carbon chain length, alkane degradation rates were medium chains > long chains > short chains. In addition, Kangiella aquimarina F7, Acinetobacter venetianus F1, Limimaricola variabilis F8, Marinobacter nauticus J5, Flavobacterium sediminis N3, and Paracoccus sediminilitoris N6 were first identified as oil-degrading bacteria from deep-sea environments. This study will provide insight into the bacterial community structures and oil-degrading bacterial diversity in the Haima cold seep areas, South China Sea, and offer bacterial resources to oil bioremediation applications.

Class 1 integron and Enterococcus spp. abundances in swine farms from the " Suckling piglets" to the "Fatteners" production category

Swine farms are considered a hotspot of antimicrobial resistance and may contribute to the spread of antibiotic-resistant and/or pathogenic bacteria into the environment as well as to farm workers. In this study, swine fecal samples have been collected over the primary production, selecting three categories, i.e., "Suckling piglets", "Weaning pigs" and "Fatteners", in six intensive swine farms, for two years. Feces were analysed for the detection and abundance of class 1 integrons (used as proxy of antibiotic resistance and of anthropogenic pollution), and of enterococci [fecal indicator bacteria (FIB) and potentially pathogenic for humans] by quantitative Real Time PCR. Furthermore, Enterococcus faecalis and Enterococcus faecium were isolated, analysed for the presence of the intI1 gene by Real Time PCR and genetically typed by Pulsed-Field Gel Electrophoresis. Both enterococci and class 1 integrons were significantly more abundant in the Suckling piglets (p = 0.0316 and 0.0242, respectively). About 8% of the isolated enterococci were positive for the intI1 gene by Real Time PCR. E. faecalis and E. faecium were found genetically heterogeneous and no specific pattern could be identified as the driver for their presence along the pig primary production. These findings suggest that the "Suckling piglets" category of production represents the key point where to mitigate the risk of transmission of enterococci and class 1 integrons with associated antibiotic resistance genes to humans and spread into the environment.

Zooplankton as a Transitional Host for Escherichia coli in Freshwater

This study shows that Escherichia coli can be temporarily enriched in zooplankton under natural conditions and that these bacteria can belong to different phylogroups and sequence types (STs), including environmental, clinical, and animal isolates. We isolated 10 E. coli strains and sequenced the genomes of two of them. Phylogenetically, the two isolates were closer to strains isolated from poultry meat than to freshwater E. coli, albeit their genomes were smaller than those of the poultry isolates. After isolation and fluorescent protein tagging of strains ED1 and ED157, we show that Daphnia sp. can take up these strains and release them alive again, thus becoming a temporary host for E. coli. In a chemostat experiment, we show that this association does not prolong bacterial long-term survival, but at low abundances it also does not significantly reduce bacterial numbers. We demonstrate that E. coli does not belong to the core microbiota of Daphnia, suffers from competition by the natural Daphnia microbiota, but can profit from its carapax to survive in water. All in all, this study suggests that the association of E. coli with Daphnia is only temporary, but the cells are viable therein, and this might allow encounters with other bacteria for genetic exchange and potential genomic adaptation to the freshwater environment.

IMPORTANCE The contamination of freshwater with feces-derived bacteria is a major concern regarding drinking water acquisition and recreational activities. Ecological interactions promoting their persistence are still very scarcely studied. This study, which analyses the survival of E. coli in the presence of zooplankton, is thus of ecological and water safety relevance.

Evaluating the potential for exposure to organisms of public health concern in naturally occurring bathing waters in Europe: A scoping review

Globally, water-based bathing pastimes are important for both mental and physical health. However, exposure to waterborne organisms could present a substantial public health issue. Bathing waters are shown to contribute to the transmission of illness and disease and represent a reservoir and pathway for the dissemination of antimicrobial resistant (AMR) organisms. Current bathing water quality regulations focus on enumeration of faecal indicator organisms and are not designed for detection of specific waterborne organisms of public health concern (WOPHC), such as antimicrobial resistant (AMR)/pathogenic bacteria, or viruses. This investigation presents the first scoping review of the occurrence of waterborne organisms of public health concern (WOPHC) in identified natural bathing waters across the European Union (EU), which aimed to critically evaluate the potential risk of human exposure and to assess the appropriateness of the current EU bathing water regulations for the protection of public health. Accordingly, this review sought to identify and synthesise all literature pertaining to a selection of bacterial (Campylobacter spp., Escherichia coli, Salmonella spp., Shigella spp., Vibrio spp., Pseudomonas spp., AMR bacteria), viral (Hepatitis spp., enteroviruses, rotavirus, adenovirus, norovirus), and protozoan (Giardia spp., and Cryptosporidium spp.) contaminants in EU bathing waters. Sixty investigations were identified as eligible for inclusion and data was extracted. Peer-reviewed investigations included were from 18 countries across the EU, totalling 87 investigations across a period of 35 years, with 30% published between 2011 and 2015. A variety of water bodies were identified, with 27 investigations exclusively assessing coastal waters. Waterborne organisms were classified into three categories; bacteria, viruses, and protozoa; amounting to 58%, 36% and 17% of the total investigations, respectively. The total number of samples across all investigations was 8,118, with detection of one or more organisms in 2,449 (30%) of these. Viruses were detected in 1281 (52%) of all samples where WOPHC were found, followed by bacteria (865(35%)) and protozoa (303(12%)). Where assessed (442 samples), AMR bacteria had a 47% detection rate, emphasising their widespread occurrence in bathing waters. Results of this scoping review highlight the potential public health risk of exposure to WOPHC in bathing waters that normally remain undetected within the current monitoring parameters.

Fecal indicator bacteria from environmental sources; strategies for identification to improve water quality monitoring

In tropical to temperate environments, fecal indicator bacteria (FIB), such as enterococci and Escherichia coli, can persist and potentially multiply, far removed from their natural reservoir of the animal gut. FIB isolated from environmental reservoirs such as stream sediments, beach sand and vegetation have been termed "naturalized" FIB. In addition, recent research suggests that the intestines of poikilothermic animals such as fish may be colonized by enterococci and E. coli, and therefore, these animals may contribute to FIB concentrations in the aquatic environment. Naturalized FIB that are derived from fecal inputs into the environment, and subsequently adapted to maintain their population within the non-host environment are termed "naturalized enteric FIB". In contrast, an additional theory suggests that some "naturalized" FIB diverged from enteric FIB many millions of years ago and are now normal inhabitants of the environment where they are referred to as "naturalized non-enteric FIB". In the case of the Escherichia genus, the naturalized non-enteric members are identified as E. coli during routine water quality monitoring. An over-estimation of the health risk could result when these naturalized, non-enteric FIB, (that is, not derived from avian or mammalian fecal contamination), contribute to water quality monitoring results. It has been postulated that these environmental FIB belonging to the genera Escherichia and Enterococcus can be differentiated from enteric FIB by genetic methods because they lack some of the genes required for colonization of the host intestine, and have acquired genes that aid survival in the environment. Advances in molecular tools such as next generation sequencing will aid the identification of genes peculiar or "enriched" in particular habitats to discriminate between enteric and environmental FIB. In this appraisal, we have reviewed the research studying "naturalized" FIB, and discussed the techniques for their differentiation from enteric FIB. This differentiation includes the important distinction between enteric FIB derived from fresh and non-recent fecal inputs, and those truly non-enteric environmental microbes, which are currently identified as FIB during routine water quality monitoring. The inclusion of tools for the identification of naturalized FIB (enteric or environmental) would be a valuable resource for future studies assessing water quality.

Antibiotic-Resistant Enterococcus Species in Marine Habitats: A Review

Antibiotic-resistant Enterococcus (ARE) are among leading causes of nosocomial infections worldwide. Enterococcus spp. are ubiquitous in sewage, which can contaminate surface waters via many pathways, providing a route of exposure for humans. This review focuses on ARE in marine and estuarine habitats, including marine animals. Phylogenetic confirmation of the genus Enterococcus and intermediate or full resistance to clinically relevant antibiotics were inclusion criteria. The proportion of resistant isolates varied greatly among antibiotics, for example, 24.2% for ampicillin and 2.4% for vancomycin. The water column contained the highest proportion of ARE observations (18.8%), followed by animal feces and tissues (14.8%), sediment (9.4%), and sand (2.0%). The proportion of multidrug-resistant isolates was the greatest in animal tissue and fecal samples, followed by water and sediments. This review indicates that clinically relevant ARE are present in marine/estuarine habitats and that animals may be important reservoirs.

Plasmid Replicon Typing of Antibiotic-Resistant Escherichia coli From Clams and Marine Sediments

Unlike human isolates, environmental Escherichia coli isolates have not been thoroughly investigated for the diversity and transferability of antibiotic-resistant plasmids. In this study, antibiotic-resistant strains from marine sediment (n = 50) and clams (n = 53) were analyzed (i) for their plasmid content using a PCR-based plasmid replicon typing (PBRT) kit and (ii) for the transferability of plasmid-associated antibiotic resistance (AR) traits by mating experiments. Fifteen of the thirty replicons targeted by the PBRT kit were detected in the isolates; 8/15 were identified in both sediment and clam isolates, although at different frequencies. The most frequent replicons in sediment (74%) and in clam strains (66%) alike, were FIA, FIB, or FII, which are associated with the IncF group, followed by the I1α replicon, which was more frequent in clam (24.5%) than in sediment (10%) strains. More than 50% of the strains contained multiple replicons; although 15 were untypable, S1-PFGE analysis demonstrated that 14/15 carried no plasmids. All cryptic strains were successfully typed and were positive for IncF or IncI replicons. Antibiotic-resistant strains accounted for 63% of all isolates and were significantly (p < 0.05) more frequent in phylogroup A. Most (35%) multidrug-resistant (MDR) strains belonged to phylogroup A, too. Although 25/26 MDR strains were positive for IncF plasmids (the exception being a clam strain), the FII-FIB rep combination was predominant (63%) among the sediment isolates, whereas most clam isolates (40%) carried the FII replicon alone. In mating experiments, selected MDR strains carrying FIB, FII, and I1α replicons, used as the donors, transferred multiple ARs together with the IncF or IncI plasmids at high frequency. Since IncI plasmids are common in E. coli and Salmonella enterica isolates from poultry, our findings suggest an animal origin to the E. coli clam strains carrying IncI plasmids. They also suggest a role for IncI plasmids in the spread of ARs among environmental Enterobacteriaceae and, through the food chain, to human isolates. In conclusion, the PBRT kit proved to be a useful tool to identify plasmids carrying antibiotic-resistant genes and to shed light on the factors underpinning their diffusion.

The evolutionary puzzle of Escherichia coli ST131

The abrupt expansion of Escherichia coli sequence type (ST) 131 is unmatched among Gram negative bacteria. In many ways, ST131 can be considered a real-world model for the complexities involved in the evolution of a multidrug resistant pathogen. While much progress has been made on our insights into the organism's population structure, pathogenicity and drug resistance profile, significant gaps in our knowledge remain. Whole genome studies have shed light on key mutations and genes that have been selected against the background of antibiotics, but in most cases such events are inferred and not supported by experimental data. Notable examples include the unknown fitness contribution made by specific plasmids, genomic islands and compensatory mutations. Furthermore, questions remain like why this organism in particular achieved such considerable success in such a short time span, compared to other more pathogenic and resistant clones. Herein, we document what is known regarding the genetics of this organism since its first description in 2008, but also highlight where work remains to be done for a truly comprehensive understanding of the biology of ST131, in order to account for its dramatic rise to prominence.

A Comprehensive Account of Escherichia coli Sequence Type 131 in Wastewater Reveals an Abundance of Fluoroquinolone-Resistant Clade A Strains

In the ten years since its discovery, the Escherichia coli clone sequence type 131 (ST131) has become a major international health threat, with the multidrug-resistant and extended-spectrum β-lactamase (ESBL)-producing clade C emerging as the globally dominant form. ST131 has previously been isolated from wastewater; however, most of these studies selectively screened for ESBL-producing organisms, thereby missing the majority of remaining ST131 clades. In this study, we used a high-throughput PCR-based screening strategy to comprehensively examine wastewater for the presence of ST131 over a 1-year period. Additional multiplex PCRs were used to differentiate clades and obtain an unbiased account of the total ST131 population structure within the collection. Furthermore, antimicrobial susceptibility profiles of all ST131-positive samples were tested against a range of commonly used antibiotics. From a total of over 3,762 E. coli wastewater samples, 1.86% (n = 70) tested positive for ST131, with the majority being clade A isolates. In total, 63% (n = 44) were clade A, 29% (n = 20) were clade B, 1% (n = 1) were clade C0, 6% (n = 4) were clade C1, and 1% (n = 1) were clade C2. In addition, a very high rate of resistance to commonly used antibiotics among wastewater isolates is reported, with 72.7% (n = 32) of clade A resistant to ciprofloxacin and high rates of resistance to gentamicin, sulfamethoxazole-trimethoprim, and tetracycline in clades that are typically sensitive to antibiotics.IMPORTANCE ST131 is a global pathogen. This clone causes urinary tract infections and is frequently isolated from human sources. However, little is known about ST131 from environmental sources. With the widely reported increase in antibiotic concentrations found in wastewater, there is additional selection pressure for the emergence of antibiotic-resistant ST131 in this niche. The unbiased screening approach reported herein revealed that previously antibiotic-sensitive lineages of ST131 are now resistant to commonly used antibiotics present in wastewater systems and may be capable of surviving UV sterilization. This is the most comprehensive account of ST131 in the wastewater niche to date and an important step in better understanding the ecology of this global pathogen.

The vertical distribution of tetA and intI1 in a deep lake is rather due to sedimentation than to resuspension

Lakes are exposed to anthropogenic pollution including the release of allochthonous bacteria into their waters. Antibiotic resistance genes (ARGs) stabilize in bacterial communities of temperate lakes, and these environments act as long-term reservoirs of ARGs. Still, it is not clear if the stabilization of the ARGs is caused by a periodical introduction, or by other factors regulated by dynamics within the water column. Here we observed the dynamics of the tetracycline resistance gene (tetA) and of the class 1 integron integrase gene intI1 a proxy of anthropogenic pollution in the water column and in the sediments of subalpine Lake Maggiore, together with several chemical, physical and microbiological variables. Both genes resulted more abundant within the bacterial community of the sediment compared to the water column and the water-sediment interface. Only at the inset of thermal stratification they reached quantifiable abundances in all the water layers, too. Moreover, the bacterial communities of the water-sediment interface were more similar to deep waters than to the sediments. These results suggest that the vertical distribution of tetA and intI1 is mainly due to the deposition of bacteria from the surface water to the sediment, while their resuspension from the sediment is less important.

Erythromycin-resistant lactic acid bacteria in the healthy gut of vegans, ovo-lacto vegetarians and omnivores

Diet can affect the diversity and composition of gut microbiota. Usage of antibiotics in food production and in human or veterinary medicine has resulted in the emergence of commensal antibiotic resistant bacteria in the human gut. The incidence of erythromycin-resistant lactic acid bacteria (LAB) in the feces of healthy vegans, ovo-lacto vegetarians and omnivores was analyzed. Overall, 155 LAB were isolated and characterized for their phenotypic and genotypic resistance to erythromycin. The isolates belonged to 11 different species within the Enterococcus and Streptococcus genera. Enterococcus faecium was the dominant species in isolates from all the dietary categories. Only 97 out of 155 isolates were resistant to erythromycin after Minimum Inhibitory Concentration (MIC) determination; among them, 19 isolates (7 from vegans, 4 from ovo-lacto vegetarians and 8 from omnivores) carried the erm(B) gene. The copresence of erm(B) and erm(A) genes was only observed in Enterococcus avium from omnivores. Moreover, the transferability of erythromycin resistance genes using multidrug-resistant (MDR) cultures selected from the three groups was assessed, and four out of six isolates were able to transfer the erm(B) gene. Overall, isolates obtained from the omnivore samples showed resistance to a greater number of antibiotics and carried more tested antibiotic resistance genes compared to the isolates from ovo-lacto vegetarians and vegans. In conclusion, our results show that diet does not significantly affect the occurrence of erythromycin-resistant bacteria and that commensal strains may act as a reservoir of antibiotic resistance (AR) genes and as a source of antibiotic resistance spreading.

Antibiotic and heavy metal resistance in enterococci from coastal marine sediment

Sediment samples from three coastal sites - two beach resorts (Beach 1 and Beach 2 sites) and an area lying between an oil refinery and a river estuary (Estuarine site) - were analyzed for antibiotic- and heavy metal (HM)-resistant enterococci. A total of 123 enterococci, 36 E. faecium, 34 E. casseliflavus, 33 E. hirae, 5 E. faecalis, 3 E. durans, 3 E. gallinarum, and 9 Enterococcus spp, were recovered. Strains resistant to erythromycin, tetracycline and quinupristin/dalfopristin (Q/D) were recovered from all sites, whereas multidrug-resistant isolates were recovered only from "Beach 2" (14%) and "Estuarine" (3.7%). As regards HM resistance, the strains showed a high frequency (68%) of cadmium and/or copper resistance and uniform susceptibility to mercury. The prevalence of cadmium-resistant strains was significantly higher among erythromycin-resistant than among erythromycin-susceptible strains. A significant association between cadmium or copper resistance and Q/D resistance was also observed at "Estuarine" site. The levels of the two HMs in sediment from all sites were fairly low, ranging from 0.070 to 0.126 μg/g, for cadmium and from 1.00 to 7.64 μg/g for copper. Mercury was always undetectable. These findings are consistent with reports that low HM concentrations may contribute to co-selection of antibiotic-resistant bacterial strains, including enterococci.

pHTβ-promoted mobilization of non-conjugative resistance plasmids from Enterococcus faecium to Enterococcus faecalis

Objectives

To analyse the recombination events associated with conjugal mobilization of two multiresistance plasmids, pRUM17i48 and pLAG (formerly named pDO1-like), from Enterococcus faecium 17i48 to Enterococcus faecalis JH2-2.

Methods

The plasmids from two E. faecalis transconjugants (JH-4T, tetracycline resistant, and JH-8E, erythromycin resistant) and from the E. faecium donor (also carrying a pHTβ-like conjugative plasmid, named pHTβ17i48) were investigated by several methods, including PCR mapping and sequencing, S1-PFGE followed by Southern blotting and hybridization, and WGS.

Results

Two locations of repApHTβ were detected in both transconjugants, one on a ∼50 kb plasmid (as in the donor) and the other on plasmids of larger sizes. In JH-4T, WGS disclosed an 88.6 kb plasmid resulting from the recombination of pHTβ17i48 (∼50 kb) and a new plasmid, named pLAG (35.3 kb), carrying the tet(M), tet(L), lsa(E), lnu(B), spw and aadE resistance genes. In JH-8E, a 75 kb plasmid resulting from the recombination of pHTβ17i48 and pRUM17i48 was observed. In both cases, the cointegrates were apparently derived from replicative transposition of an IS1216 present in each of the multiresistance plasmids into pHTβ17i48. The cointegrates could resolve to yield the multiresistance plasmids and a pHTβ17i48 derivative carrying an IS1216 (unlike the pHTβ17i48 of the donor).

Conclusions

Our results completed the characterization of the multiresistance plasmids carried by the E. faecium 17i48, confirming the role of pHT plasmids in the mobilization of non-conjugative antibiotic resistance elements among enterococci. Results also revealed that mobilization to E. faecalis was associated with the generation of cointegrate plasmids promoted by IS1216-mediated transposition.

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

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.

Defence strategies and antibiotic resistance gene abundance in enterococci under stress by exposure to low doses of peracetic acid

Peracetic acid (PAA) is an organic compound used efficiently as disinfectant in wastewater treatments. Yet, at low doses it may cause selection; thus, the effect of low doses of PAA on Enterococcus faecium as a proxy of human-related microbial waste was evaluated. Bacteria were treated with increasing doses of PAA (from 0 to 25 mg L^-1 min) and incubated in regrowth experiments under non-growing, limiting conditions and under growing, favorable conditions. The changes in bacterial abundance, in bacterial phenotype (number and composition of small cell clusters), and in the abundance of an antibiotic resistance gene (ARG) was evaluated. The experiment demonstrated that the selected doses of PAA efficiently removed enterococci, and induced a long-lasting effect after PAA inactivation. The relative abundance of small clusters increased during the experiment when compared with that of the inoculum. Moreover, under growing favorable conditions the relative abundance of small clusters decreased and the number of cells per cluster increased with increasing PAA doses. A strong stability of the measured ARG was found, not showing any effect during the whole experiment. The results demonstrated the feasibility of low doses of PAA to inactivate bacteria. However, the stress induced by PAA disinfection promoted a bacterial adaptation, even if potentially without affecting the abundance of the ARG.

Comparison of droplet digital PCR and quantitative PCR for the detection of Salmonella and its application for river sediments

Despite advances in microbial detection that quantitative polymerase chain reaction (qPCR) has led to, complex environmental samples, such as sediments, remain a challenge due to presence of PCR inhibitors. Aquatic sediments accumulate particle-bound microbial contaminants and thereby reflect a cumulative microbial load over time. The relatively new droplet digital PCR (ddPCR) has emerged as a direct quantitative method, highly tolerant to PCR inhibitors and relinquishing the necessity for calibration/standard curves. Information is virtually absent where ddPCR has been applied to detect pathogenic organisms in aquatic sediments. This study compared the efficacy of ddPCR with qPCR, for quantification of Salmonella in sediments from the Palmiet River near an informal settlement in Durban, South Africa. ddPCR significantly improved both analytical sensitivity and detection of low concentrations of Salmonella as compared to qPCR. The expected copy numbers measured from both qPCR and ddPCR showed good R² values (0.999 and 0.994, respectively). The site mostly affected by the informal settlements exhibited Salmonella in the range of 255 ± 37 and 818 ± 30 Salmonella/g (p ≤ 0.0001) in qPCR and ddPCR, respectively. The improved detection of Salmonella in sediments with ddPCR makes it a promising technical method for the quantification of Salmonella in multifarious environmental samples.

Evaluation of Molecular Methods for the Detection and Quantification of Pathogen-Derived Nucleic Acids in Sediment

The accurate detection of pathogens in environmental matrices, such as sediment, is critical in understanding pathogen fate and behavior in the environment. In this study, we assessed the usefulness of methods for the detection and quantification of Vibrio spp. and norovirus (NoV) nucleic acids in sediment. For bacteria, a commonly used direct method using hexadecyltrimethylammonium bromide (CTAB) and phenol-chloroform-isoamyl alcohol (PCI) extraction was optimized, whereas for NoV, direct and indirect (virus elution-concentration) methods were evaluated. For quantification, commercially available quantitative PCR (qPCR) and reverse transcription qPCR (RT-qPCR) kits were tested alongside a digital PCR (dPCR) approach. CTAB-based extraction combined with 16 h polyethylene glycol 6000 (PEG6000) precipitation was found to be suitable for the direct extraction of high abundance bacterial and viral nucleic acids. For the indirect extraction of viral RNA, beef extract-based elution followed by PEG6000 precipitation and extraction using the NucliSENS® MiniMag® Nucleic Acid Purification System and the PowerViral® Environmental RNA/DNA Isolation Kit and qRT-PCR resulted in 83-112 and 63-69% recoveries of NoV, respectively. dPCR resulted in lower viral recoveries (47 and 9%) and ~4 orders of magnitude lower Vibrio concentrations (3.6-4.6 log10 gc/100 g sediment) than was observed using qPCR. The use of internal controls during viral quantification revealed that the RT step was more affected by inhibitors than the amplification. The methods described here are suitable for the enumeration of viral and/or bacterial pathogens in sediment, however the use of internal controls to assess efficiency is recommended.

Abundance and Distribution of Enteric Bacteria and Viruses in Coastal and Estuarine Sediments-a Review

The long term survival of fecal indicator organisms (FIOs) and human pathogenic microorganisms in sediments is important from a water quality, human health and ecological perspective. Typically, both bacteria and viruses strongly associate with particulate matter present in freshwater, estuarine and marine environments. This association tends to be stronger in finer textured sediments and is strongly influenced by the type and quantity of clay minerals and organic matter present. Binding to particle surfaces promotes the persistence of bacteria in the environment by offering physical and chemical protection from biotic and abiotic stresses. How bacterial and viral viability and pathogenicity is influenced by surface attachment requires further study. Typically, long-term association with surfaces including sediments induces bacteria to enter a viable-but-non-culturable (VBNC) state. Inherent methodological challenges of quantifying VBNC bacteria may lead to the frequent under-reporting of their abundance in sediments. The implications of this in a quantitative risk assessment context remain unclear. Similarly, sediments can harbor significant amounts of enteric viruses, however, the factors regulating their persistence remains poorly understood. Quantification of viruses in sediment remains problematic due to our poor ability to recover intact viral particles from sediment surfaces (typically <10%), our inability to distinguish between infective and damaged (non-infective) viral particles, aggregation of viral particles, and inhibition during qPCR. This suggests that the true viral titre in sediments may be being vastly underestimated. In turn, this is limiting our ability to understand the fate and transport of viruses in sediments. Model systems (e.g., human cell culture) are also lacking for some key viruses, preventing our ability to evaluate the infectivity of viruses recovered from sediments (e.g., norovirus). The release of particle-bound bacteria and viruses into the water column during sediment resuspension also represents a risk to water quality. In conclusion, our poor process level understanding of viral/bacterial-sediment interactions combined with methodological challenges is limiting the accurate source apportionment and quantitative microbial risk assessment for pathogenic organisms associated with sediments in aquatic environments.

Enterococcus faecium ST17 from Coastal Marine Sediment Carrying Transferable Multidrug Resistance Plasmids

The multidrug-resistant Enterococcus faecium 17i48, sequence type 17, from marine sediment, carrying erm(B), tet(M), and tet(L) genes, was analyzed for the presence of antibiotic resistance plasmids and for the ability to transfer resistance genes. The strain was found to harbor the replicon type (repA) of pRE25, pRUM, pHTβ, and the axe-txe toxin-antitoxin (TA) system. In mating experiments, tet(M) and tet(L) were cotransferred with the repA_pRE25, whereas erm(B) was consistently cotransferred with the axe-txe and repA_pRUM, suggesting that tetracycline and erythromycin resistance genes were carried on different elements both transferable by conjugation, likely via pHTβ-mediated mobilization. Hybridization and PCR mapping demonstrated that tet(M) and tet(L) were located in tandem on a pDO1-like plasmid that also carried the repA_pRE25, whereas erm(B) was carried by a pRUM-like plasmid. Sequencing of the latter plasmid showed a high nucleotide identity with pRUM and the presence of cat, aadE, sat4, and a complete aphA resistance genes. These findings show that the genetic features of E. faecium 17i48 are consistent with a hospital-adapted clone and suggest that antibiotic resistance may spread in the environment, also in the absence of antibiotic pressure, due to TA system plasmid maintenance.

What happens in hospitals does not stay in hospitals: antibiotic-resistant bacteria in hospital wastewater systems

Hospitals are hotspots for antimicrobial-resistant bacteria (ARB) and play a major role in both their emergence and spread. Large numbers of these ARB will be ejected from hospitals via wastewater systems. In this review, we present quantitative and qualitative data of extended-spectrum β-lactamase (ESBL)-producing Escherichia coli, vancomycin-resistant enterococci and Pseudomonas aeruginosa in hospital wastewaters compared to community wastewaters. We also discuss the fate of these ARB in wastewater treatment plants and in the downstream environment. Published studies have shown that hospital effluents contain ARB, the burden of these bacteria being dependent on their local prevalence. The large amounts of antimicrobials rejected in wastewater exert a continuous selective pressure. Only a few countries recommend the primary treatment of hospital effluents before their discharge into the main wastewater flow for treatment in municipal wastewater treatment plants. Despite the lack of conclusive data, some studies suggest that treatment could favour the ARB, notably ESBL-producing E. coli. Moreover, treatment plants are described as hotspots for the transfer of antibiotic resistance genes between bacterial species. Consequently, large amounts of ARB are released in the environment, but it is unclear whether this release contributes to the global epidemiology of these pathogens. It is reasonable, nevertheless, to postulate that it plays a role in the worldwide progression of antibiotic resistance. Antimicrobial resistance should now be seen as an 'environmental pollutant', and new wastewater treatment processes must be assessed for their capability in eliminating ARB, especially from hospital effluents.

Antimicrobial and Anti-Virulence Activity of Capsaicin Against Erythromycin-Resistant, Cell-Invasive Group A Streptococci

Capsaicin (8-methyl-N-vanillyl-6-nonenamide) is the active component of Capsicum plants (chili peppers), which are grown as food and for medicinal purposes since ancient times, and is responsible for the pungency of their fruit. Besides its multiple pharmacological and physiological properties (pain relief, cancer prevention, and beneficial cardiovascular, and gastrointestinal effects) capsaicin has recently attracted considerable attention because of its antimicrobial and anti-virulence activity. This is the first study of its in vitro antibacterial and anti-virulence activity against Streptococcus pyogenes (Group A streptococci, GAS), a major human pathogen. The test strains were previously characterized, erythromycin-susceptible (n = 5) and erythromycin-resistant (n = 27), cell-invasive pharyngeal isolates. The MICs of capsaicin were 64–128 μg/mL (the most common MIC was 128 μg/mL). The action of capsaicin was bactericidal, as suggested by MBC values that were equal or close to the MICs, and by early detection of dead cells in the live/dead assay. No capsaicin-resistant mutants were obtained in single-step resistance selection studies. Interestingly, growth in presence of sublethal capsaicin concentrations induced an increase in biofilm production (p ≤ 0.05) and in the number of bacteria adhering to A549 monolayers, and a reduction in cell-invasiveness and haemolytic activity (both p ≤ 0.05). Cell invasiveness fell so dramatically that a highly invasive strain became non-invasive. The dose-response relationship, characterized by opposite effects of low and high capsaicin doses, suggests a hormetic response. The present study documents that capsaicin has promising bactericidal activity against erythromycin-resistant, cell-invasive pharyngeal GAS isolates. The fact that sublethal concentrations inhibited cell invasion and reduced haemolytic activity, two important virulence traits of GAS, is also interesting, considering that cell-invasive, erythromycinresistant strains can evade β-lactams by virtue of intracellular location and macrolides by virtue of resistance, thus escaping antibiotic treatment. By inhibiting intracellular invasion and haemolytic activity, capsaicin could thus prevent both formation of a difficult to eradicate intracellular reservoir, and infection spread to deep tissues.

High prevalence of multiple-antibiotic-resistant (MAR) Escherichia coli in river bed sediments of the Apies River, South Africa

This study aimed at investigating the presence of antibiotic-resistant Escherichia coli in river bed sediments of the Apies River, Gauteng, South Africa, in order to better inform health management decisions designed to protect users of the river. Overall, 180 water and sediment samples were collected at 10 sites along the Apies River from January to February 2014. E. coli was enumerated using the Colilert® 18/Quanti-Tray® 2000 (IDEXX). Isolates were purified by streaking on eosin methylene blue agar followed by the indole test. Pure E. coli isolates were tested for resistance to nine antibiotics by the Kirby-Bauer disc diffusion method. Over 98% of the isolates were resistant to at least one of the antibiotics tested. The highest resistance was observed against nitrofurantoin (sediments) and ampicillin (water). Over 80% of all resistant isolates showed multiple antibiotic resistance (resistance to ≥3 antibiotics). The abundance of E. coli in the sediments not only adds to the evidence that sediments are a reservoir for bacteria and possibly other pathogens including antibiotic-resistant bacteria but also suggests that antibiotic-resistant genes could be transferred to pathogens due to the high prevalence of multiple-antibiotic-resistant (MAR) strains of E. coli observed in the sediment. Using untreated water from the Apies River following resuspension for drinking and other household purposes could pose serious health risks for users. Our results suggest that river bed sediments could serve as reservoirs for MAR bacteria including pathogens under different climatic conditions and their analysis could provide information of public health concerns.

Understanding the association of Escherichia coli with diverse macroalgae in the lagoon of Venice

Recent studies provided evidence that the macroalga Cladopohora in lakes hosts associated Escherichia coli, with consequences on the environmental and human health. We expanded these investigations to other macroalgae (Ulva spp., Sargassum muticum and Undaria pinnatifida) widespread in the lagoon of Venice (Italy). Attached E. coli were abundant, accounting up to 3,250 CFU gram⁻¹ of alga. Macroalgal-associated isolates belonged to all E. coli phylogroups, including pathogenic ones, and to Escherichia cryptic clades. Attached E. coli showed potential to grow even at in situ temperature on macroalgal extracts as only source of carbon and nutrients, and ability to produce biofilm in vitro. The genotypic diversity of the attached isolates was high, with significant differences between algae and the overlying water. Our evidences suggest that attached populations consist of both resident and transient strains, likely resulting from the heterogeneous input of fecal bacteria from the city. We report that cosmopolitan and invasive macroalgae may serve as source of E. coli, including pathogenic genotypes, and that this habitat can potentially support their growth. Considering the global diffusion of the macroalgae here studied, this phenomenon is likely occurring in other coastal cities worldwide and deserves further investigations from either the sanitary and ecological perspectives.

Escherichia coli ST131, an intriguing clonal group

In 2008, a previously unknown Escherichia coli clonal group, sequence type 131 (ST131), was identified on three continents. Today, ST131 is the predominant E. coli lineage among extraintestinal pathogenic E. coli (ExPEC) isolates worldwide. Retrospective studies have suggested that it may originally have risen to prominence as early as 2003. Unlike other classical group B2 ExPEC isolates, ST131 isolates are commonly reported to produce extended-spectrum β-lactamases, such as CTX-M-15, and almost all are resistant to fluoroquinolones. Moreover, ST131 E. coli isolates are considered to be truly pathogenic, due to the spectrum of infections they cause in both community and hospital settings and the large number of virulence-associated genes they contain. ST131 isolates therefore seem to contradict the widely held view that high levels of antimicrobial resistance are necessarily associated with a fitness cost leading to a decrease in pathogenesis. Six years after the first description of E. coli ST131, this review outlines the principal traits of ST131 clonal group isolates, based on the growing body of published data, and highlights what is currently known and what we need to find out to provide public health authorities with better information to help combat ST131.

Adhesion of marine cryptic Escherichia isolates to human intestinal epithelial cells

Five distinct cryptic lineages (clades I-V) have recently been recognized in the Escherichia genus. The five clades encompass strains that are phenotypically and taxonomically indistinguishable from Escherichia coli sensu stricto; however, scant data are available on their ecology, virulence and pathogenic properties. In this study 20 cryptic E. coli strains isolated from marine sediments were investigated to gain insights into their virulence characteristics and genetic traits. The ability to adhere to intestinal cells was highest among clade V strains, which also harbored the genes involved in gut colonization as well as the genes (pduC and eut operon) typically found in environmentally adapted E. coli strains. The pduC gene was significantly associated with clade V. Multilocus sequence typing of three representative clade V isolates revealed new sequence types (STs) and showed that the strains shared two allelic loci (adk 51 and recA 37). Our findings suggest that cryptic Escherichia lineages are common in coastal marine sediments and that this habitat may be suitable for their growth and persistence outside the host. On the other hand, detection in clade V strains of a gene repertoire and adhesion properties similar to those of intestinal pathogenic strains could indicate their potential virulence. It could be argued that there is a dual nature of cryptic clade V strains, where the ability to survive and persist in a secondary habitat does not involve the loss of the host-associated lifestyle. Clade V could be a group of closely related, environmentally adapted E. coli strains.

A new clone sweeps clean: the enigmatic emergence of Escherichia coli sequence type 131

Escherichia coli sequence type 131 (ST131) is an extensively antimicrobial-resistant E. coli clonal group that has spread explosively throughout the world. Recent molecular epidemiologic and whole-genome phylogenetic studies have elucidated the fine clonal structure of ST131, which comprises multiple ST131 subclones with distinctive resistance profiles, including the (nested) H30, H30-R, and H30-Rx subclones. The most prevalent ST131 subclone, H30, arose from a single common fluoroquinolone (FQ)-susceptible ancestor containing allele 30 of fimH (type 1 fimbrial adhesin gene). An early H30 subclone member acquired FQ resistance and launched the rapid expansion of the resulting FQ-resistant subclone, H30-R. Subsequently, a member of H30-R acquired the CTX-M-15 extended-spectrum beta-lactamase and launched the rapid expansion of the CTX-M-15-containing subclone within H30-R, H30-Rx. Clonal expansion clearly is now the dominant mechanism for the rising prevalence of both FQ resistance and CTX-M-15 production in ST131 and in E. coli generally. Reasons for the successful dissemination and expansion of the key ST131 subclones remain undefined but may include increased transmissibility, greater ability to colonize and/or persist in the intestine or urinary tract, enhanced virulence, and more-extensive antimicrobial resistance compared to other E. coli. Here we discuss the epidemiology and molecular phylogeny of ST131 and its key subclones, possible mechanisms for their ecological success, implications of their widespread dissemination, and future research needs.

Prevalence of enterococcus species and their virulence genes in fresh water prior to and after storm events

Enterococcus spp. isolates (n = 286) collected from six surface water bodies in subtropical Brisbane, Australia, prior to and after storm events, were identified to species level and tested for the presence of seven clinically important virulence genes (VGs). Enterococcus faecalis (48%), Enterococcus faecium (14%), Enterococcus mundtii (13%), and Enterococcus casseliflavus (13%) were frequently detected at all sites. The frequency of E. faecium occurrence increased from 6% in the dry period to 18% after the wet period. The endocarditis antigen (efaA), gelatinase (gelE), collagen-binding protein (ace), and aggregation substance (asa1) were detected in 61%, 43%, 43%, and 23% of Enterococcus isolates, respectively. The chances of occurrence of ace, gelE, efaA, and asa1 genes in E. faecalis were found to be much higher compared to the other Enterococcus spp. The observed odds ratio of occurrence of ace and gelE genes in E. faecalis was much higher at 7.96 and 6.40 times, respectively. The hyl gene was 3.84 times more likely to be detected in E. casseliflavus. The presence of multiple VGs in most of the E. faecalis isolates underscores the importance of E. faecalis as a reservoir of VGs in the fresh water aquatic environment. Consequently, if contaminated surface water is to be used for production of potable and nonpotable water some degree of treatment depending upon intended use such as detention in basins prior to use or chlorination is required.