Survival of enterococcal species in aquatic environments

Antimicrobial resistance characterization of Enterococcus faecium, Enterococcus faecalis and Enterococcus hirae isolated from marine coastal recreational waters in the State of São Paulo, Brazil

Coastal water quality is facing increasing threats due to human activities. Their contamination by sewage discharges poses significant risks to the environment and public health. We aimed to investigate the presence of antibiotic-resistant Enterococcus in beach waters. Over a 10-month period, samples were collected from four beaches in the State of São Paulo (Brazil). Enterococcus isolates underwent matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF/MS) and molecular analysis for accurate genus and species identification. The antimicrobial susceptibility for 14 antibiotics was evaluated using the disc diffusion method followed by a multidrug-resistance (MDR) classification. PCR amplification method was used to detect antimicrobial resistance genes (ARGs). Our findings revealed the prevalence of Enterococcus faecalis, E. faecium and E. hirae. Out of 130 isolates, 118 were resistant to multiple antibiotics. The detection of resistance genes provided evidence of the potential transfer of antibiotic resistance within the environment. Our findings underscore the necessity for continuous research and surveillance to enhance understanding of the pathogenicity and antimicrobial resistance mechanisms of Enterococcus, which is crucial to implement effective measures to preserve the integrity of coastal ecosystems.

The risk of viable but non-culturable (VBNC) enterococci and antibiotic resistance transmission during simulated municipal sludge composting

Sludge composting is a sludge resource utilization method that can reduce pollutants, such as pathogens. Enterococci are regarded as more reliable and conservative indicators of pathogen inactivation than fecal coliforms, which are typically used as indicators of fecal pollution. Non-spore pathogenic bacteria may enter a viable but non-culturable (VBNC) state during composting, leading to residual risk. The VBNC status of bacteria is related to their survival during composting. However, the survival mechanisms of enterococci during sludge composting remain unclear. Therefore, this study aimed to investigate the VBNC state of enterococci in different phases of simulated sludge composting and the fate of antibiotic resistance genes (ARGs) and mobile genetic elements (MGEs) during the composting process. This study is expected to provide a basis for subsequent exploration of possible methods to completely inactivate enterococci and reduce ARGs during sludge composting. Culturable enterococci were reduced in the thermophilic phase of sludge composting, but the proportion of VBNC subpopulation increased. It was reported for the first time that most VBNC enterococci were killed by extending the cooling phase of sludge compost, and by prolonging the cooling phase the types of ARG were reduced. However, there was a certain quantity (approximately 104/g dry weight) of culturable and VBNC enterococci in the compost products. In addition, MGEs and ARGs exist in both bacteria and compost products, leading to the risk of spreading antibiotic-resistant bacteria and antibiotic resistance when sludge compost products are used.

Enterococcus faecium: evolution, adaptation, pathogenesis and emerging therapeutics

The opportunistic pathogen Enterococcus faecium colonizes humans and a wide range of animals, endures numerous stresses, resists antibiotic treatment and stubbornly persists in clinical environments. The widespread application of antibiotics in hospitals and agriculture has contributed to the emergence of vancomycin-resistant E. faecium, which causes many hospital-acquired infections. In this Review, we explore recent discoveries about the evolutionary history, the environmental adaptation and the colonization and dissemination mechanisms of E. faecium and vancomycin-resistant E. faecium. These studies provide critical insights necessary for developing novel preventive and therapeutic approaches against vancomycin-resistant E. faecium and also reveal the intricate interrelationships between the environment, the microorganism and the host, providing knowledge that is broadly relevant to how antibiotic-resistant pathogens emerge and endure.

How suitable is freshwater sponge Ephydatia fluviatilis (Linnaeus, 1759) for time-integrated biomonitoring of microbial water quality?

Faecal pollution of water by bacteria has a negative effect on water quality and can pose a potential health hazard. Conventional surveillance of microbial water quality relies on the analysis of low-frequency spot samples and is thus likely to miss episodic or periodic pollution. This study aimed to investigate the potential of filter-feeding sponges for time-integrated biomonitoring of microbial water quality. Laboratory trials tested the effects of different ratios of bacterial abundance and the sequence of exposure on bacterial retention by the freshwater sponge Ephydatia fluviatilis (Linnaeus, 1759) to establish its potential to indicate bacterial exposure. Gemmule grown sponges were simultaneously exposed to Escherichia coli and Enterococcus faecalis but at different ratios (Trial 1) or individually exposed to each bacterial species but in different sequential order (Trial 2). The E. coli and E. faecalis retained in each sponge was quantified by culture on selective agars. Data analysis was conducted using the Kruskal-Wallis test and/or the Mann-Whitney U test to compare between the numbers of bacteria retained in each treatment. Additionally, the Wilcoxon matched-paired signed-rank test was used for comparison of the different bacterial abundances retained within each individual sponge. Sponges from all trials retained E. coli and E. faecalis in small numbers relative to the exposure (<0.05 % Trial 1 and <0.07 % Trial 2) but exhibited higher retention of E. coli. Higher abundance of either bacterial species resulted in significantly lower (P<0.005) retention of the same species within sponges (Trial 1). An initial exposure to E. coli resulted in significantly higher (P=0.040) retention of both bacterial species than when sponges were exposed to E. faecalis first (Trial 2).Bacterial retention by sponges was neither quantitatively representative of bacterial abundance in the ambient water nor the sequence of exposure. This implies either selective filtration or an attempt by sponges to prevent infection. However, freshwater sponges may still be useful in biomonitoring as qualitative time-integrated samplers of faecal indicator bacteria as they detect different bacteria present in the water even if their quantities cannot be estimated.

Effects of chlorination on the survival of sewage bacteria in seawater microcosms

Chlorination is a commonly used disinfection method in sewage treatment process. However, resistant bacteria may survive chlorination and enter the receiving aquatic environment upon effluent discharge. There has been limited research on the effects of chlorination on bacterial survival in seawater. To address this knowledge gap, microcosm experiments were conducted to simulate the discharge of chlorinated effluents into coastal seawater. The results revealed that bacterial communities in seawater-based effluents survived better in seawater than those in freshwater-based effluents. High chlorine dosages could significantly reduce the viable bacterial populations and their chance of regrowth in seawater. Additionally, faecal indicator bacteria (FIB) that entered the viable but non-culturable (VBNC) state under chlorination tended to persist in the VBNC state without resuscitation during seawater incubation. Because of the prevalence of VBNC indicator bacteria, qPCR quantification of FIB was more effective than conventional culture-based methods in tracing viable pathogenic chlorine-resistant bacteria, although the correlation strength varied depending on the type of effluent. This study sheds light on how chlorine dosages and the intrinsic properties of effluents affect bacterial survival in seawater and highlights the potential and limitations of using FIB in monitoring the health risks associated with the discharge of chlorinated effluents.

Diversity of Fecal Indicator Enterococci among Different Hosts: Importance to Water Contamination Source Tracking

Enterococcus spp. are common bacteria present in the intestinal tracts of animals and are used as fecal indicators in aquatic environments. On the other hand, enterococci are also known as opportunistic pathogens. Elucidating their composition in the intestinal tracts of domestic animals can assist in estimating the sources of fecal contamination in aquatic environments. However, information on the species and composition of enterococci in animal hosts (except humans) is still lacking. In this study, enterococci were isolated from the feces of cattle, pigs, birds, and humans using selective media. Enterococcal species were identified using mass spectrometry technology, and each host was characterized by diversity and cluster analysis. The most dominant species were E. hirae in cattle, E. faecium in birds, and E. faecalis in pigs and humans. Cattle had the highest alpha diversity, with high interindividual and livestock farm diversity. The dominant enterococcal species in pigs and humans were identical, and cluster analysis showed that the majority of the two hosts' species clustered together.

Prevalence of Class 1 Integron and In Vitro Effect of Antibiotic Combinations of Multidrug-Resistant Enterococcus Species Recovered from the Aquatic Environment in the Eastern Cape Province, South Africa

Enterococci are regarded as a better indication of faecal pollution in freshwater and marine waters. Their levels in seawater are positively connected with swimming-related gastrointestinal disorders. This study used an Enterococcus-specific polymerase chain reaction (PCR) to characterize the isolates. Classes 1 and 2 integrons were examined for environmental Enterococcus isolates using a standard biological procedure. All strains were assessed against a panel of 12 antibiotics from various classes using disc diffusion methods. The microdilution method was used to work out the minimum inhibitory concentration (MIC) according to the CLSI guiding principles. The combination therapy of the resistant drugs was evaluated using a checkerboard assay and a time-dependent test for assessing their bactericidal or bacteriostatic activity. The gene diversity of the tested organisms was analyzed with the aid of Enterobacterial Repetitive Intergenic Consensus (ERIC) PCR. In total, 57 Enterococcus spp. environmental samples were recovered, in which Enterococcus faecalis (33.33%) and Enterococcus faecium (59.65%) were the dominant species. Resistance to linezolid, ciprofloxacin, erythromycin, gentamicin, vancomycin, rifampicin, and tetracycline was prevalent. Fifty (50) strains tested positive for class 1 integron, more frequent in Enterococcus faecium and Enterococcus faecalis isolates, with no gene cassette array discovered. A combination of gentamicin (MIC 4 µg/mL) with vancomycin (MIC 256 µg/mL) antibiotics against Enterococcus faecalis showed antibacterial activity. In contrast, the combination of ciprofloxacin (1 µg/mL) with Ampicillin (16 µg/mL) antibiotics against Enterococcus faecalis showed a bacteriostatic effect. The ERIC-PCR analysis pointed out that most of the assessed isolates have close genetic similarities.

Molecular Typing Reveals Environmental Dispersion of Antibiotic-Resistant Enterococci under Anthropogenic Pressure

As a consequence of global demographic challenges, both the artificial and the natural environment are increasingly impacted by contaminants of emerging concern, such as bacterial pathogens and their antibiotic resistance genes (ARGs). The aim of this study was to determine the extent to which anthropogenic contamination contributes to the spread of antibiotic resistant enterococci in aquatic compartments and to explore genetic relationships among Enterococcus strains. Antimicrobial susceptibility testing (ampicillin, imipenem, norfloxacin, gentamycin, vancomycin, erythromycin, tetracycline, trimethoprim-sulfamethoxazole) of 574 isolates showed different rates of phenotypic resistance in bacteria from wastewaters (91.9–94.4%), hospital effluents (73.9%), surface waters (8.2–55.3%) and groundwater (35.1–59.1%). The level of multidrug resistance reached 44.6% in enterococci from hospital effluents. In all samples, except for hospital sewage, the predominant species were E. faecium and E. faecalis. In addition, E. avium, E. durans, E. gallinarum, E. aquimarinus and E. casseliflavus were identified. Enterococcus faecium strains carried the greatest variety of ARGs (bla_TEM-1, aac(6′)-Ie-aph(2″), aac(6′)-Im, vanA, vanB, ermB, mefA, tetB, tetC, tetL, tetM, sul1), while E. avium displayed the highest ARG frequency. Molecular typing using the ERIC2 primer revealed substantial genetic heterogeneity, but also clusters of enterococci from different aquatic compartments. Enterococcal migration under anthropogenic pressure leads to the dispersion of clinically relevant strains into the natural environment and water resources. In conclusion, ERIC-PCR fingerprinting in conjunction with ARG profiling is a useful tool for the molecular typing of clinical and environmental Enterococcus species. These results underline the need of safeguarding water quality as a strategy to limit the expansion and progression of the impending antibiotic-resistance crisis.

Antimicrobial Biocides Susceptibility and Tolerance-Associated Genes in Enterococcus faecalis and Enterococcus faecium Isolates Collected from Human and Environmental Sources

Enterococci are among the most common causes of nosocomial infections worldwide. Antimicrobial biocides are extensively used to control the growth of microorganisms on different surfaces. The purpose of this study was to determine the susceptibility of Enterococcus faecalis and Enterococcus faecium isolates collected in Iran to biocide agents, formaldehyde (FOR), benzalkonium chloride (BZC), triclosan (TRE), and chlorhexidine digluconate (CHDG). Additionally, the frequency of biocide tolerance-associated (BTA) genes, qacA/B, qacED1, emeA, sigV and gasp65 were investigated. In this study, 222 isolates of E. faecalis and 425 isolates of E. faecium from clinical and non-clinical sources were investigated. Minimum inhibitory concentration (MIC) of biocide agents was determined using agar dilution method. Biocides epidemiological cutoff values (ECOFFs) were determined using 95% rule. BTA genes were identified using PCR testing. ECOFFs for CHDG, BZC, TRE and FOR were 8 µg/mL, 16 µg/mL, 32 µg/mL and 512 µg/mL for both species, respectively. MIC values showed that the distribution of isolates with high level of tolerance to antimicrobial biocides was clearly different, depending on ecological niches. The BTA genes, qacA/B, qacED1, emeA, sigV and gasp65 were detected in 19.4% (43), 19.8% (44), 42.8% (95), 89.6% (199) and 70.2% (156) of E. faecalis and 10.3% (44), 17.2% (73), 27.8% (118), 42.2% (188) and 82.8% (352) of E. faecium isolates, respectively. Based on the distribution pattern of BTA genes 14 and 18 different profiles were identified for E. faecalis and E. faecium isolates respectively. Generally, the isolates carrying at least a single BTA gene showed higher MIC₉₀ against all biocides compared to isolates with no BTA genes. However, there were no clear association between MIC₉₀ values and carrying particular BTA genes profile. The results of this study showed that CHDG was the most effective biocide against E. faecalis and E. faecium isolates. The data presented in current study can be used to define the biocides resistance breakpoints.

Lilium spp., as unnoticed environmental vector, spreading OptrA-carrying Enterococcus spp

Flower is an essential element in the human lifestyle but its role in disseminating antimicrobial resistance (AMR) between the environment and humans is unclear. In this study, we screened fresh flowers (Lilium spp.) collected from planting bases, market and florists in Guangzhou China aiming to investigate the prevalence of AMR genes, particularly cfr, optrA and poxtA mediating resistance to linezolid, a first-line drug for the treatment of different Gram-positive bacterial infections. We found 223 Enterococcus isolates consisting of Enterococcus faecalis, Enterococcus faecium and Enterococcus mundtii, and >50% of these isolates exhibited multiple-drug resistance. Additionally, 31 optrA-positive Enterococcus including 22 E. faecalis and 9 E. mundtii strains were recovered, however cfr and poxtA were not detected. The 22 E. faecalis strains were belonged to 7 Multilocus sequence types in which ST202 and ST376 were predominant and 9 E. mundtii strains from the same plantation bases were divided into three PFGE groups. Genetically, the majority of optrA were located on the chromosome and shared similar insertion sites and transpositions mediated by Tn554 family members. Plasmid-bearing optrA were identified in 6 E. faecalis strains where IS1216 family played key roles in horizontal transfer of optrA. These findings emphasize that the prevalence of drug resistant Enterococcus in fresh flowers is a latent danger and increases the risk of AMR dissemination to humans from the environment.

Assessment of listing and categorisation of animal diseases within the framework of the Animal Health Law (Regulation (EU) No 2016/429): antimicrobial-resistant Enterococcus faecalis in poultry

Enterococcus faecalis (E. faecalis) was identified among the most relevant antimicrobial-resistant (AMR) bacteria in the EU for poultry in a previous scientific opinion. Thus, it has been assessed according to the criteria of the Animal Health Law (AHL), in particular criteria of Article 7 on disease profile and impacts, Article 5 on its eligibility to be listed, Annex IV for its categorisation according to disease prevention and control rules as in Article 9 and Article 8 for listing animal species related to the bacterium. The assessment has been performed following a methodology previously published. The outcome is the median of the probability ranges provided by the experts, which indicates whether each criterion is fulfilled (lower bound ≥ 66%) or not (upper bound ≤ 33%), or whether there is uncertainty about fulfilment. Reasoning points are reported for criteria with uncertain outcome. According to the assessment here performed, it is uncertain whether AMR E. faecalis can be considered eligible to be listed for Union intervention according to Article 5 of the AHL (33-66% probability). According to the criteria in Annex IV, for the purpose of categorisation related to the level of prevention and control as in Article 9 of the AHL, the AHAW Panel concluded that the bacterium does not meet the criteria in Sections 1, 2 and 4 (Categories A, B and D; 0-5%, 5-10% and 1-10% probability of meeting the criteria, respectively) and the AHAW Panel is uncertain whether it meets the criteria in Sections 3 and 5 (Categories C and E, 33-66% and 33-66% probability of meeting the criteria, respectively). The animal species to be listed for AMR E. faecalis according to Article 8 criteria are mostly birds of the orders Galliformes and Anseriformes, but also mammals and reptiles can serve as reservoirs.

Coastal Surveillance and Water Quality monitoring in the Rejiche Sea-Tunisia

The aim of this study is to determine physiochemical and bacteriological properties of seawater and sediments from the coast of Tunisia during six successive months. The conductivity was measured using previously calibrated Hach Conductivity meter. Total suspended solid was determined using Whatman GF/C glass fiber filter (Sigma Aldrich), and the turbidity was assessed using a spectrophotometer (UV/Vis). The pH was measured using pH electrodes. Other physiochemical parameters were determined using Pastel UV multiparameter water analyzer (Secomam, aqualabo). Bacterial analysis was displayed by membrane filtration method, and isolates were identified to the species level by Api strips. Susceptibility to antibiotics was determined by disk diffusion methods. Total suspended solid, turbidity, adsorbable organic halogen, chemical oxygen demand, and biochemical oxygen demand were higher than accepted norms in Tunisia. Enterococcus faecalis was detected in all the sites indicating a human fecal contamination, and all the isolates were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin, and azithromycin. The situation in Mahdia coast is alarming particularly with the isolation of multidrug resistance strains. It is recommended that the local government provide restrict policies for the treatment and the assessment of municipal wastewater before its discharge into sea. PRACTITIONER POINTS: Coastal Surveillance and Water Quality monitoring in the Rejiche Sea - Tunisia is crucial. Enterococcus faecalis was detected in sea water and sediment samples in the coast of Rejiche. Isolated strains were highly resistant to rifampicin, gentamicin, chloramphenicol, ampicillin and azithromycin.

Pathogen and Surrogate Survival in Relation to Fecal Indicator Bacteria in Freshwater Mesocosms

The microbial quality of agricultural water for fresh produce production is determined by the presence of the fecal indicator bacterium (FIB) Escherichia coli, despite poor correlations with pathogen presence. Additional FIB, such as enterococci, have been utilized for assessing water quality. The study objective was to determine the survival times (first time to detect zero or censored) of FIB (E. coli and enterococci), surrogates (Listeria innocua, Listeria seeligeri, Salmonella enterica serovar Typhimurium, and PRD1), and pathogens (four strains each of pathogenic E. coli and Listeria monocytogenes and five Salmonella serovars) simultaneously inoculated in freshwater mesocosms exposed to diel and seasonal variations. Six separate mesocosm experiments were conducted for ≤28 days each season, with samples (sediment/water) collected each day for the first 7 days and weekly thereafter. Microorganisms survived significantly longer in sediment than in water (hazard ratio [HR] for water/sediment is 2.2; 95% confidence interval [CI], 1.79 to 2.71). Also, FIB E. coli survived significantly longer than FIB enterococcus (HR for enterococci/E. coli is 12.9 [95% CI, 8.18 to 20.37]) after adjusting for the sediment/water and lake/river effects. Differences in the area under the curve (calculated from log CFU or PFU over time) were used to assess pathogen and surrogate survival in relation to FIB. Despite sample type (sediment/water) and seasonal influences, survival rates of pathogenic Salmonella serovars were similar to those of FIB E. coli, and survival rates of L. monocytogenes and pathogenic E. coli were similar to those of FIB enterococci. Further investigation of microbial survival in water and sediment is needed to determine which surrogates are best suited to assess pathogen survival in agricultural water used in irrigation water for fresh produce. IMPORTANCE Contamination of fresh produce via agricultural water is well established. This research demonstrates that survival of fecal indicator bacteria, pathogenic microorganisms, and other bacterial and viral surrogates in freshwater differs by sample type (sediment/water) and season. Our work highlights potential risks associated with pathogen accumulation and survival in sediment and the possibility for resuspension and contamination of agricultural water used in fresh produce production. Specifically, a greater microbial persistence in sediments than in water over time was observed, along with differences in survival among microorganisms in relation to the fecal indicator bacteria E. coli and enterococci. Previous studies compared data among microbial groups in different environments. Conversely, fecal indicator bacteria, surrogates, and pathogenic microorganisms were assessed within the same water and sediment mesocosms in the present study during four seasons, better representing the agricultural aquatic environment. These data should be considered when agricultural microbial water quality criteria in fresh produce operations are being determined.

Current Trends of Enterococci in Dairy Products: A Comprehensive Review of Their Multiple Roles

As a genus that has evolved for resistance against adverse environmental factors and that readily exchanges genetic elements, enterococci are well adapted to the cheese environment and may reach high numbers in artisanal cheeses. Their metabolites impact cheese flavor, texture, and rheological properties, thus contributing to the development of its typical sensorial properties. Due to their antimicrobial activity, enterococci modulate the cheese microbiota, stimulate autolysis of other lactic acid bacteria (LAB), control pathogens and deterioration microorganisms, and may offer beneficial effects to the health of their hosts. They could in principle be employed as adjunct/protective/probiotic cultures; however, due to their propensity to acquire genetic determinants of virulence and antibiotic resistance, together with the opportunistic character of some of its members, this genus does not possess Qualified Presumption of Safety (QPS) status. It is, however, noteworthy that some putative virulence factors described in foodborne enterococci may simply reflect adaptation to the food environment and to the human host as commensal. Further research is needed to help distinguish friend from foe among enterococci, eventually enabling exploitation of the beneficial aspects of specific cheese-associated strains. This review aims at discussing both beneficial and deleterious roles played by enterococci in artisanal cheeses, while highlighting the need for further research on such a remarkably hardy genus.

Particle association of Enterococcus sp. increases growth rates and simulated persistence in water columns of varying light attenuation and turbulent diffusivity

Predicting water quality and the human health risks associated with sewage-derived microbes requires understanding the fate and transport of these contaminants. Sewage-derived pathogen risks are typically assessed and monitored by measuring concentrations of fecal indicating bacteria (FIB), like Enterococcus sp. Previous research demonstrated that a high fraction of FIB is particle-associated, which can alter FIB dynamics within secondary water bodies. In this study, we experimentally quantified the effect of particle association on dark, temperature- and light-dependent growth and sinking rates of enterococci. Particle association significantly increased dark growth rates, light-dependent growth rates (i.e. decreased mortality), and sinking rates, relative to free-living enterococci. Simulations using a novel, 1-dimensional model parameterized by these rates indicate greater persistence (T₉₀) for particle-associated enterococci in water bodies across a wide range of diffuse attenuation coefficients of light (K_d) and turbulent diffusivity (D) values. In addition, persistence of both fractions increased in simulated turbid and turbulent waters, compared to clear and/or quiescent conditions. Simulated persistence of both fractions also increased when enterococci discharges occurred later in a diel cycle (towards sunset, as opposed to sunrise), especially for the free-living population, because later discharges under our model conditions allowed both fractions to mix deeper before inactivation via sunlight. Model sensitivity testing revealed that T₉₀ variability was greatest when dark growth rates were altered, suggesting that future empirical studies should focus on quantifying these rates for free-living and particle-associated sewage-derived microbes. Despite greater sensitivity of T₉₀ to variability in dark growth rates, omitting light-dependent growth rates from simulations dramatically influenced T₉₀ values. Our results demonstrate that particle association can increase enterococci persistence in receiving waters and highlight the importance of incorporating particle association in future water quality models.

Fermented Seeds ("Zgougou") from Aleppo Pine as a Novel Source of Potentially Probiotic Lactic Acid Bacteria

Microorganisms inhabiting fermented foods represent the main link between the consumption of this food and human health. Although some fermented food is a reservoir of potentially probiotic microorganisms, several foods are still unexplored. This study aimed at characterizing the probiotic potential of lactic acid bacteria isolated from zgougou, a fermented matrix consisting of a watery mixture of Aleppo pine's seeds. In vitro methods were used to characterize the safety, survival ability in typical conditions of the gastrointestinal tract, and adherence capacity to surfaces, antimicrobial, and antioxidant activities. Strains belonged to the Lactobacillus plantarum group and Enterococcus faecalis showed no DNase, hemolytic, and gelatinase activities. In addition, their susceptibility to most of the tested antibiotics, satisfied some of the safety prerequisites for their potential use as probiotics. All the strains tolerated low pH, gastrointestinal enzymes, and bile salts. They displayed a good antibacterial activity and antibiofilm formation against 10 reference bacterial pathogens, especially when used as a cell-free supernatant. Furthermore, the lactic acid bacteria (LAB) strains inhibited the growth of Aspergillus flavus and Aspergillus carbonarius. Finally, they had good antioxidant activity, although depending on the strain. Overall, the results of this work highlight that zgougou represents an important reservoir of potentially probiotic LAB. Obviously, future studies should be addressed to confirm the health benefits of the LAB strains.

Microbial uptake kinetics of dissolved organic carbon (DOC) compound groups from river water and sediments

Dissolved organic matter (DOM) represents a key component of carbon (C) cycling in freshwater ecosystems. While the behaviour of bulk dissolved organic carbon (DOC) in aquatic ecosystems is well studied, comparatively little is known about the turnover of specific DOC compounds. The aim of this study was to investigate the persistence of ¹⁴C-labelled low molecular weight (LMW) DOC at a wide range of concentrations (0.1 µM to 10 mM), in sediments and waters from oligotrophic and mesotrophic rivers within the same catchment. Overall, rates of DOC loss varied between compound groups (amino acids > sugars = organic acids > phenolics). Sediment-based microbial communities contributed to higher DOC loss from river waters, which was attributed, in part, to its greater microbial biomass. At higher DOC compound concentrations, DOC loss was greater in mesotrophic rivers in comparison to oligotrophic headwaters. A lag-phase in substrate use within sediments provided evidence of microbial growth and adaptation, ascribed here to the lack of inorganic nutrient limitation on microbial C processing in mesotrophic communities. We conclude that the higher microbial biomass and available inorganic nutrients in sediments enables the rapid processing of LMW DOC, particularly during high C enrichment events and in N and P-rich mesotrophic environments.

A Pure Life: The Microbial Ecology of High Purity Industrial Waters

The microbial ecology of various natural environments has been an active area of research since the earlier part of the twentieth century. Remote and sometimes extreme environments such as the deep ocean and the deep terrestrial subsurface have revealed a remarkable array of microorganisms. The majority of these environments are nutrient limited, and microorganisms-principally, bacteria-have developed a number of survival strategies that enable their survival and, in some cases, replication. While planktonic microorganisms exist in oligotrophic environments, the predominant mode of survival and growth is associated with biofilms. There are a number of similarities between the physicochemistry of industrial water systems and some natural aquatic ecosystems, and these similarities extend to the microbial populations and the survival mechanisms that are employed. The "starvation-survival" mechanisms, including biofilm formation, may be associated with deleterious effects on industrial water systems. These effects include heat transfer inhibition, microbially influenced corrosion, and contamination of various products manufactured in a wide array of industries. Biological fouling of industrial water systems has significant direct and indirect (through antimicrobial chemical applications) impacts on engineered materials and on the etiology of some waterborne diseases. This review provides an overview of the microbial ecology of purified waters and discusses the impacts of biological activity on industrial systems.

Transcriptome Changes of Escherichia coli, Enterococcus faecalis, and Escherichia coli O157:H7 Laboratory Strains in Response to Photo-Degraded DOM

In this study, we investigated gene expression changes in three bacterial strains (Escherichia coli C3000, Escherichia coli O157:H7 B6914, and Enterococcus faecalis ATCC 29212), commonly used as indicators of water quality and as control strains in clinical, food, and water microbiology laboratories. Bacterial transcriptome responses from pure cultures were monitored in microcosms containing water amended with manure-derived dissolved organic matter (DOM), previously exposed to simulated sunlight for 12 h. We used RNA sequencing (RNA-seq) and quantitative real-time reverse transcriptase (qRT-PCR) to compare differentially expressed temporal transcripts between bacteria incubated in microcosms containing sunlight irradiated and non-irradiated DOM, for up to 24 h. In addition, we used whole genome sequencing simultaneously with RNA-seq to identify single nucleotide variants (SNV) acquired in bacterial populations during incubation. These results indicate that E. coli and E. faecalis have different mechanisms for removal of reactive oxygen species (ROS) produced from irradiated DOM. They are also able to produce micromolar concentrations of H₂O₂ from non-irradiated DOM, that should be detrimental to other bacteria present in the environment. Notably, this study provides an assessment of the role of two conjugative plasmids carried by the E. faecalis and highlights the differences in the overall survival dynamics of environmentally-relevant bacteria in the presence of naturally-produced ROS.

Effect of salinity on medium- and low-pressure UV disinfection of Vibrio cholerae

The problem of biological invasions attributed to ballast water release is an ongoing problem that threatens ecosystems and human health. Ultraviolet (UV) radiation has been increasingly used for ballast water treatment mainly due to the advantages of short contact time and minimized harmful disinfection by products. In this study, the impact of salinity on the inactivation of Vibrio cholerae (NCTC 7253) was examined, and comparison of inactivation level and disinfection kinetics after medium-pressure (MP) (1 kW) and low-pressure (LP) (10 W) UV irradiation was made. MP UV exposure resulted in higher inactivation efficacy against V. cholerae than LP UV exposure especially at lower UV doses (≤3 mJ cm^-2) and salinity had a negative impact on both MP and LP UV disinfection, especially at higher UV doses (≥3 mJ cm^-2 for MP and ≥4 mJ cm^-2 for LP). To understand the mechanisms of salinity effect on V. cholerae, the enzyme-linked immunosorbent assay (ELISA) was employed to determine the number of cyclobutane pyrimidine dimers (CPDs), one major type of DNA damage. No significant effects of salinity were found at the CPDs level except for 3% artificial seawater after LP UV exposure case. It is imperative that site-specific conditions of salinity be taken into account in the design of UV reactors to treat V. cholerae and other species.

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.

A loop-mediated isothermal amplification (LAMP) assay for the rapid detection of Enterococcus spp. in water

Faecal pollution of water and the resulting potential presence of human enteric pathogens is a predominant threat to public health. Microbiological water quality can be assessed by the detection of standard faecal indicator bacteria (SFIB) such as E. coli or certain Enterococcus species. In recent years, isothermal amplification methods have become a useful alternative to polymerase chain reaction (PCR), allowing molecular diagnostics with simple or no instrumentation. In this study, a novel screening method for the molecular detection of Enterococcus spp. by loop-mediated isothermal amplification (LAMP) is described. A set of six specific LAMP primers was designed to amplify a diagnostic fragment of the Enterococcus 23S rRNA gene, which is present in several enterococcal species targeted by quantitative PCR (qPCR), which is the standard technique recommended by the US Environmental Protection Agency. Sensitivity and specificity tests were performed using a set of 30 Enterococcus and non-target bacterial reference strains. It is shown that LAMP is equally sensitive and even more specific than the qPCR assay. A dilution series of Enterococcus faecalis DNA revealed that the LAMP method can reliably detect 130 DNA target copies per reaction within 45 min. Additionally, enterococci isolated from Austrian surface waterbodies, as well as a set of DNA extracts from environmental waters, were tested. Contingency analysis demonstrated a highly significant correlation between the results of the developed LAMP assay and the reference qPCR method. Furthermore, a simple staining procedure with a fluorescence dye demonstrated the identification of amplified products by eye. In conclusion, this method is an important component for the efficient screening and testing of water samples in low-resource settings lacking sophisticated laboratory equipment and highly trained personnel, requiring only a simple heating block.

Effects of water quality on inactivation and repair of Microcystis viridis and Tetraselmis suecica following medium-pressure UV irradiation

The transfer of invasive organisms by ballast-water discharge has become a growing concern. UV treatment has become an attractive ballast water treatment technology due to its effectiveness, no harmful disinfection byproducts and easiness to handle. Two robust algae strains Microcystis viridis and Tetraselmis suecica were selected as indicator organisms to determine efficiency of medium-pressure (MP) UV-treatment on ballast water. Inactivation and potential repair of these two algae strains following MP UV irradiation were assessed under various turbidity, total organic carbon (TOC) and salinity conditions. The investigated range of UV doses was from 25 to 500 mJ/cm(2). For M. viridis, results indicated that disinfection efficiency was negatively correlated with all of these three factors at low doses (25-200 mJ/cm(2)). Photoreactivation and dark repair were promoted at high TOC levels (6-15 mg/L) with about 6-25% higher repair levels compared with those in distilled water, whereas no significant impacts were identified for turbidity and salinity on both of the photoreactivation and dark repair. For T. suecica, increased turbidity and TOC levels both hindered the performance of UV irradiation at high doses (200-500 mJ/cm(2)). Suppressive effects on photoreactivation and dark repair were consistently observed with changes of all of the three factors. In conclusion, generally these three factors resulted in repressive effects on UV disinfection efficiency, and TOC played a more significant role in the levels of reactivation than the other two. The responses of T. suecica to these three factors were more sensitive than M. viridis.

Temporal Variabilities in Genetic Patterns and Antibiotic Resistance Profiles of Enterococci Isolated from Human Feces

Temporal variabilities in the genetic patterns and antibiotic resistance profiles of enterococci were monitored over a 7-month period. Enterococcus faecalis isolates (103 strains) collected from feces showed only one genetic pattern and antibiotic resistance profile within 0 d and 30 d. In contrast, after 60 d and 90 d, the genetic patterns and antibiotic resistance profiles of all E. faecalis isolates (8 strains) clearly differed within 30 d. These results indicate that the genetic patterns and antibiotic resistance profiles of E. faecalis in human feces changed to completely dissimilar patterns between 1 and 2 months.

Antibiotic susceptibilities of enterococcus species isolated from hospital and domestic wastewater effluents in alice, eastern cape province of South Africa

Background: Antimicrobial resistance in microorganisms are on the increase worldwide and are responsible for substantial cases of therapeutic failures. Resistance of species of Enterococcus to antibiotics is linked to their ability to acquire and disseminate antimicrobial resistance determinants in nature, and wastewater treatment plants (WWTPs) are considered to be one of the main reservoirs of such antibiotic resistant bacteria. We therefore determined the antimicrobial resistance and virulence profiles of some common Enterococcus spp that are known to be associated with human infections that were recovered from hospital wastewater and final effluent of the receiving wastewater treatment plant in Alice, Eastern Cape. Methods: Wastewater samples were simultaneously collected from two sites (Victoria hospital and final effluents of a municipal WWTP) in Alice at about one to two weeks interval during the months of July and August 2014. Samples were screened for the isolation of enterococci using standard microbiological methods. The isolates were profiled molecularly after targeted generic identification and speciation for the presence of virulence and antibiotic resistance genes. Results: Out of 66 presumptive isolates, 62 were confirmed to belong to the Enterococcus genusof which 30 were identified to be E. faecalis and 15 E. durans. The remaining isolates were not identified by the primers used in the screening procedure. Out of the six virulence genes that were targeted only three of them; ace, efaA, and gelE were detected. There was a very high phenotypic multiple resistance among the isolates and these were confirmed by genetic analyses. Conclusions: Analyses of the results obtained indicated that hospital wastewater may be one of the sources of antibiotic resistant bacteria to the receiving WWTP. Also, findings revealed that the final effluent discharged into the environment was contaminated with multi-resistant enterococci species thus posing a health hazard to the receiving aquatic environment as these could eventually be transmitted to humans and animals that are exposed to it.

Modified 16S-23S rRNA intergenic region restriction endonuclease analysis for species identification of Enterococcus strains isolated from pigs, compared with identification using classical methods and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry

Fast and reliable identification of bacteria to at least the species level is currently the basis for correct diagnosis and appropriate treatment of infections. This is particularly important in the case of bacteria of the genus Enterococcus, whose resistance profile is often correlated with their species (e.g. resistance to vancomycin). In this study, we evaluated restriction endonuclease analysis of the 16S-23S rRNA gene intergenic transcribed spacer (ITS) region for species identification of Enterococcus. The utility of the method was compared with that of phenotypic methods [biochemical profile evaluation and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS)]. Identification was based on 21 Enterococcus reference strains, of the species E. faecalis, E. faecium, E. hirae, E. durans, E. casseliflavus, E. gallinarum, E. avium, E. cecorum and E. columbae, and 47 Enterococcus field strains isolated from pigs. Restriction endonuclease analysis of the ITS-PCR product using HinfI, RsaI and MboI, in the order specified, enabled species differentiation of the Enterococcus reference and field strains, and in the case of the latter, the results of species identification were identical (47/47) to those obtained by MALDI-TOF MS. Moreover, as a result of digestion with MboI, a unique restriction profile was also obtained for the strains (3/3) identified by MALDI-TOF MS as E. thailandicus. In our opinion, restriction endonuclease analysis of the 16S-23S rRNA gene ITS region of Enterococcus may be a simple and relatively fast (less than 4 h) alternative method for identifying the species occurring most frequently in humans and animals.

Identification of Enterococcus faecium and Enterococcus faecalis as vanC-type Vancomycin-Resistant Enterococci (VRE) from sewage and river water in the provincial city of Miyazaki, Japan

As a first step for assessing the risk to human health posed by vancomycin-resistant enterococci (VRE) in the aquatic environment, we screened sewage and urban river water samples from Miyazaki, Japan for VRE. Because vancomycin-resistant organisms are not as prevalent in sewage and river water as vancomycin-susceptible organisms, the samples were screened by minimum inhibitory concentration test using the vancomycin-supplemented membrane-Enterococcus indoxyl-β-d-glucoside (mEI) agar. The isolates, presumed to be enterococci, were identified using 16S rRNA sequencing analysis. The percentages of VRE isolates screened using 4 μg mL(-1) vancomycin-supplemented mEI agar from sewage and urban river water samples were 12% and 24%, respectively. The vancomycin-resistant genes vanC1 and vanC2/3 were detected in the isolates from both samples by PCR analysis. All enterococci isolates containing vanC1, which is a specific gene for vanC-type of VRE, were identified as Enterococcus casseliflavus/gallinarum. Further, 92% enterococci isolates containing vanC2/3 were identified as E. casseliflavus/gallinarum, the remaining isolates containing vanC2/3 were E. faecium (4%) and E. faecalis (4%). Thereafter, the distribution of E. faecium and E. faecalis, which are the major types of enterococci in humans containing vanC2/3, was observed in the water samples collected.

Quantification of vancomycin-resistant enterococci and corresponding resistance genes in a sewage treatment plant

This study aimed to analyze vancomycin-resistant enterococci (VRE) and their resistance genes, vanA and vanB, to examine their presence in sewage treatment systems. Water samples were collected from primary sedimentation tank inlet, aeration tank, final sedimentation tank overflow outlet, and disinfection tank. Enterococcal strains were determined their vancomycin susceptibility by the minimum inhibitory concentration (MIC) test. Vancomycin-resistance genes (vanA and vanB) were quantified by real-time PCR. The sewage treatment process indeed decreased the number of most enterococci contained in the entering sewage, with a removal rate of ≥ 5 log. The MIC test showed that two enterococcal strains resistant to a high concentration of vancomycin (>128 μg mL(-1)). However, most of the enterococcal strains exhibited sensitivity to vancomycin, indicating that VRE were virtually absent in the sewage treatment systems. On the other hand, vancomycin-resistance genes were detected in all the sewage samples, including those collected from the chlorination disinfection tank. The highest copy numbers of vanA (1.5 × 10(3) copies mL(-1)) and vanB (1.0 × 10(3) copies mL(-1)) were detected from the water sample of effluent water and chlorinated water, respectively. Therefore, antibiotic resistance genes remain in the sewage treatment plant and might discharged into water environments such as rivers and coastal areas.

Identification and antimicrobial resistance of Enterococcus spp. isolated from the river and coastal waters in northern Iran

As fecal streptococci commonly inhabit the intestinal tract of humans and warm blooded animals, and daily detection of all pathogenic bacteria in coastal water is not practical, thus these bacteria are used to detect the fecal contamination of water. The present study examined the presence and the antibiotic resistance patterns of Enterococcus spp. isolated from the Babolrud River in Babol and coastal waters in Babolsar. Seventy samples of water were collected in various regions of the Babolrud and coastal waters. Isolated bacteria were identified to the species level using standard biochemical tests and PCR technique. In total, 70 Enterococcus spp. were isolated from the Babolrud River and coastal waters of Babolsar. Enterococcus faecalis (68.6%) and Enterococcus faecium (20%) were the most prevalent species. Resistance to chloramphenicol, ciprofloxacin, and tetracyclin was prevalent. The presence of resistant Enterococcus spp. in coastal waters may transmit resistant genes to other bacteria; therefore, swimming in such environments is not suitable.

Environmental and animal-associated enterococci

Enterococci are generally commensal bacteria inhabiting the gastrointestinal tract of humans and animals. They have, however, been implicated as the etiological agent of a variety of illnesses and nosocomial infections. In addition to pathogenic potential, there is growing concern regarding the incidence of antibiotic resistance and genetic exchange among Enterococcus spp. within and among a variety of animal hosts. While primarily considered an enteric group, extra-enteric habitats in which enterococci persist and potentially grow have been studied for decades. Although many biotic (e.g., predation) and abiotic (e.g., sunlight, nutrients, and salinity) stressors have been thought to limit the success of enterococci in these secondary habitats, a growing body of evidence suggests that certain strains may become naturalized to environmental habitats. Enterococci have also been used for decades as indicators of fecal contamination in recreational waters where increased concentrations of this group have been linked to the incidence of illness in humans following recreational use of these waters. Persistence of enterococci in secondary habitats, however, suggests that their presence in ambient waters may prove to be a poor indicator of actual risks to public health. In this chapter, we provide a review of the existing body of literature concerning animal host associations, genetic exchange is reviewed, and emphasis is placed on the growing body of evidence for the persistence and growth of enterococci in secondary habitats.

Regrowth of enterococci indicator in an open recycled-water impoundment

The purpose of the research was to assess the potential for enterococci faecal-indicator to regrow in recycled water while under environmentally-open storage. Regrowth would result in false-positive indicator results with possible downgrading, rejection or over-chlorination of recycled water. The research setting was the main 93-megalitre storage impoundment of the Hawkesbury Water Recycling Scheme in Sydney's North West, receiving tertiary treated (chlorinated) effluent from the Richmond sewage treatment plant. The water is used to irrigate horticultural food crops, pasture for dairy cattle, sheep, deer and horses, and for the maintenance of lawns and sports fields. Highly significant positive relationships were noted in multivariate analysis between indicator counts and the growth factors atmospheric temperature and UV254 unfiltered as proxy for total organic carbon (p=0.001 and 0.003 respectively). Nitrate and phosphate did not show significant relationships suggesting that these nutrients may not be growth-limiting at levels found in recycled water. Rainfall and wild duck presence did not appear to have an impact on enterococcal growth in the study. The overall predictive power of the regression model was shown to be highly significant (p=0.001). These findings will assist in recycled water monitoring and the revision of guidelines, with potential for the reduction of the chlorination by-product burden on the environment. A formula derived for the relationship between the indicator and atmospheric temperature could be used in food-production and climate-change modelling.

Detection of vancomycin-resistant enterococci (VRE) at four U.S. wastewater treatment plants that provide effluent for reuse

Vancomycin-resistant enterococci (VRE), a leading cause of hospital-acquired infections, can occur in wastewater. However, to date, no previous studies have evaluated the occurrence of VRE at wastewater treatment plants (WWTPs) that send their treated effluent to reuse sites. We evaluated the occurrence, concentration, and antimicrobial resistance patterns of VRE at U.S. WWTPs associated with reuse sites. We collected 44 wastewater samples, representing treatment steps from influent to effluent, from two Mid-Atlantic and two Midwest WWTPs between October 2009 and October 2010. Samples were analyzed for total enterococci and VRE using membrane filtration. Isolates were confirmed using biochemical tests and PCR. Antimicrobial susceptibility testing was performed by Sensititre microbroth dilution. Data were analyzed by two-sample proportion tests and analysis of variance. We detected VRE in 27% (12/44) of all wastewater samples collected and VRE represented 3% of total enterococci detected at all WWTPs. More samples were VRE-positive from the Mid-Atlantic compared to the Midwest WWTPs (p=0.008). VRE concentrations decreased as treatment progressed at all WWTPs, except at Mid-Atlantic WWTP1 where there was an increase in VRE concentrations in activated sludge reactor samples. VRE were not detected in chlorinated effluent, but were detected in one un-chlorinated effluent sample. All unique VRE isolates were multidrug resistant. Fifty-five percent (12/22) of the isolates displayed high-level aminoglycoside resistance. Our findings show that chlorination reduces the occurrence of VRE in wastewater. However, WWTP workers could be exposed to VRE during wastewater treatment. Our data also raise potential concerns about VRE exposure among individuals who come into contact with un-chlorinated reclaimed water.

A proposal for source tracking of fecal pollution in recreational waters by pulsed-field gel electrophoresis

This study aimed to identify specific river sources of fecal contamination by applying pulsed-field gel electrophoresis (PFGE) to environmental water samples from a recreational beach in Japan. The genotypes of all Enterococcus faecium and Enterococcus faecalis strains used as indicators of fecal pollution on the recreational beach and rivers were analyzed by PFGE, and the PFGE profiles of the strains were classified at a 0.9 similarity level using dendrogram analysis. PFGE types of E. faecium isolated from Sakai River or urban drainage were classified in the same cluster. Therefore, the probable sources of fecal pollution on the recreational beach were Sakai River and urban drainage. The approaches for microbial source tracking employed in this study used PFGE with Enterococcus species as an indicator can be a potential tool to specify the source(s) of fecal pollution and contribute to improved public health in coastal environments.

Enterococci in the environment

Enterococci are common, commensal members of gut communities in mammals and birds, yet they are also opportunistic pathogens that cause millions of human and animal infections annually. Because they are shed in human and animal feces, are readily culturable, and predict human health risks from exposure to polluted recreational waters, they are used as surrogates for waterborne pathogens and as fecal indicator bacteria (FIB) in research and in water quality testing throughout the world. Evidence from several decades of research demonstrates, however, that enterococci may be present in high densities in the absence of obvious fecal sources and that environmental reservoirs of these FIB are important sources and sinks, with the potential to impact water quality. This review focuses on the distribution and microbial ecology of enterococci in environmental (secondary) habitats, including the effect of environmental stressors; an outline of their known and apparent sources, sinks, and fluxes; and an overview of the use of enterococci as FIB. Finally, the significance of emerging methodologies, such as microbial source tracking (MST) and empirical predictive models, as tools in water quality monitoring is addressed. The mounting evidence for widespread extraenteric sources and reservoirs of enterococci demonstrates the versatility of the genus Enterococcus and argues for the necessity of a better understanding of their ecology in natural environments, as well as their roles as opportunistic pathogens and indicators of human pathogens.

Fate of pathogenic bacteria in microcosms mimicking human body sites

During the infectious process, pathogens may reach anatomical sites where they are exposed to substances interfering with their growth. These substances can include molecules produced by the host, and his resident microbial population, as well as exogenous antibacterial drugs. Suboptimal concentrations of inhibitory molecules and stress conditions found in vivo (high or low temperatures, lack of oxygen, extreme pH) might induce in bacteria the activation of survival mechanisms blocking their division capability but allowing them to stay alive. These "dormant" bacteria can be reactivated in particular circumstances and would be able to express their virulence traits. In this study, it was evaluated the effect of some environmental conditions, such as optimal and suboptimal temperatures, direct light and antibiotic sub-inhibitory concentrations doses of antibiotic, on the human pathogens Escherichia coli and Enterococcus faecalis when incubated in fluids accumulated in the body of patients with different pathologies. It is shown that inoculation in a number of accumulated body fluids and the presence of gentamicin, reliable conditions encountered during pathological states, induce stress-responding strategies enabling bacteria to persist in microcosms mimicking the human body. Significant differences were detected in Gram-negative and Gram-positive species with E. faecalis surviving, as starved or viable but non-culturable forms, in any microcosm and condition tested and E. coli activating a viable but non-culturable state only in some clinical samples. The persistence of bacteria under these conditions, being non-culturable, might explain some recurrent infections without isolation of the causative agent after application of the standard microbiological methods.

Modeling the effect of light and salinity on viable but non-culturable (VBNC) Enterococcus

Enterococci have been recommended as suitable bacteria indicators for assessing the microbial quality of recreational waters. However, recent studies have shown that bacteria, including enterococci, are able to enter a viable but non-culturable (VBNC) state under environmentally stressed conditions, where they may remain undetected if culture-based methods are employed. To appreciate the extent of transformation of these cells in surface waters, a model Enterococcus organism, E. faecalis, was examined in laboratory controlled microcosms under different light and salinity conditions. Cells were detected by both standard culture-based and PMA-qPCR (propidium monoazide quantitative PCR) methods so that the VBNC cells could be enumerated. The decay rates from the culture based method (kc) and PMA-qPCR method (kp) were established for the different conditions. In general, the kC values (ranging from 0.0088 hr(-1) to 0.9755 hr(-1)) were always higher than the kP values (0.0019 hr(-1) to 0.2373 hr(-1)), implying that cells were able to retain their viability for much longer periods than what is shown by the culture-based method. In both cases, the k values generally showed an increasing trend with an increase in light irradiation, implying greater die-off with light. For freshwater microcosms, the kp values were 3-6 times lower than the kc values for different irradiation conditions, whereas for seawater the difference was up to 12 times, showing that E. faecalis adapts well to seawater. The kinetic data were used to develop models to describe the dynamics of VBNC formation in natural waters. At low light intensities (less than about 20 Wm(-2)), the proportion of VBNC cells was found to steadily increase to as high as 50%, even after 4 days. However, at higher light levels, this proportion was achieved more quickly (less than 5 h) but also diminished more rapidly. Hence, at high light levels, the percentage of VBNC cells is expected to be significant only for a few hours, whereas at low light levels, the VBNC cells can be expected to be present for a long period of time. These results have implications on the interpretation of microbial water quality data that are based on culture based methods.

High incidence of antibiotic multi-resistant bacteria in coastal areas dedicated to fish farming

Marine bacteria exposed to antibiotics in fish farms can acquire antimicrobial resistance by mobile genetic elements and horizontal gene transfer. A total of 872 autochthonous marine bacterial strains was isolated from samples collected from four different fish farms located at northern and southern Italian Adriatic Sea. Resistance to only tetracycline (17%) and to trimethoprim-sulfadiazine (7%) were the most frequent patterns obtained, while flumequine resistance has recorded in only 0.3% of the strains. Comparing strains isolated from coastal areas and fish farms, a significant higher incidence (4% versus 10%) of multi-resistant strains in aquaculture centers was found. Significant differences in antibiotic resistance incidence were also detected among the four fish farms due probably to different approaches in farm management and the more or less frequent use of antibiotics. Antibiotic-resistant and multi-resistant strains isolated constitute an environmental reservoir directly involved in the seafood chain and might represent a public health concern.

Detection and genotyping of vancomycin-resistant Enterococcus spp. by multiplex polymerase chain reaction in Korean aquatic environmental samples

The distribution characteristics of Enterococcus spp., which are indicators of fecal pollution, were investigated at 33 sites within the 3 major water systems of Korea. Enterococci were detected at concentrations ranging from 1 to 37 CFU/100mL in 41 of 132 samples (31.1%) from the 3 major water systems. The overall average detected concentration was 1.2 CFU/100mL, while the average concentration for all detection sites was 5.3 CFU/100mL. After optimized multiplex polymerase chain reaction (PCR) was performed with newly developed VanA, VanB, VanC-1, and VanC-2/3 primers, concentrations of vancomycin-resistant Enterococcus spp. (VRE) ranging from 1 to 23 CFU/100mL were detected in 17 of 132 samples (12.9%). Of 216 individual enterococcal colonies, 64 (29.6%) displayed the VanC genotype. The results of a susceptibility test to vancomycin showed that the range of the minimal inhibitory concentration (MIC), an indicator of bacterial resistance, was 4 to 24μg/mL, with the average MIC at 9.2±4.5μg/mL. Of the bacterial isolates, 1 colony with the VanC-1 genotype was identified as E. gallinarum by 16S rDNA sequencing, whereas the other 63 colonies had the VanC-2/3 genotype and were identified as E. casseliflavus. Although these results imply that the major head bays of Korea are not contaminated with the highly vancomycin-resistant VanA- or VanB-type VREs, the misuse of antibiotics should be prohibited to minimize the presence of VREs and to maintain a safe water supply for protecting the health of the general population. Based on the study results, we also recommend the implementation of a continuous, broad-spectrum inspection program for Enterococcus spp. and VRE contamination in the major head bays. Furthermore, the multiplex PCR method described in this study can be used effectively for this purpose.

Dramatic improvements in beach water quality following gull removal

Gulls are often cited as important contributors of fecal contamination to surface waters, and some recreational beaches have used gull control measures to improve microbial water quality. In this study, gulls were chased from a Lake Michigan beach using specially trained dogs, and water quality improvements were quantified. Fecal indicator bacteria and potentially pathogenic bacteria were measured before and during gull control using culture methods and quantitative polymerase chain reaction (qPCR). Harassment by dogs was an effective method of gull control: average daily gull populations fell from 665 before to 17 during intervention; and a significant reduction in the density of a gull-associated marker was observed (p < 0.001). Enterococcus spp. and Escherichia coli densities were also significantly reduced during gull control (p < 0.001 and p = 0.012, respectively for culture methods; p = 0.012 and p = 0.034, respectively for qPCR). Linear regression results indicate that a 50% reduction in gulls was associated with a 38% and 29% decrease in Enterococcus spp. and E. coli densities, respectively. Potentially human pathogenic bacteria were detected on 64% of days prior to gull control and absent during gull intervention, a significant reduction (p = 0.005). This study demonstrates that gull removal can be a highly successful beach remedial action to improve microbial water quality.

Persistence and growth of the fecal indicator bacteria enterococci in detritus and natural estuarine plankton communities

Enterococci are used to evaluate recreational-water quality and health risks in marine environments. In addition to their occurrence in feces of warm blooded animals, they are also common epiphytes. We investigated the contribution of plankton- or particle-associated enterococci in estuarine and coastal water. Seven water and size-fractionated plankton samples were collected monthly between April 2008 and January 2009 in the tidal reaches of the Skidaway River (Georgia, USA). Each size fraction, along with filtered (<30 μm) and bulk estuarine water, was processed according to U.S. Environmental Protection Agency method 1600. Presumptive enterococci were selected and species were identified using carbon substrate utilization patterns. The highest average densities occurred within the 30-, 63-, 105-, and 150-μm size fractions, which also represented the majority (>99%) of the particles within the sampled water. Particle-associated enterococci accounted for as little as 1% of enterococci in bulk water in April to as much as 95% in July. Enterococcus faecalis was the most commonly isolated species from both water and plankton and represented 31% (16/51) and 35% (6/17) of the identified Enterococcus species from water and plankton, respectively. Enterococcus casseliflavus represented 29% of the selected isolates from plankton and 16% from water. Both E. faecalis and E. casseliflavus were able to survive and grow in plankton suspensions significantly longer than in artificial seawater. Enterococcus spp. may be highly concentrated in plankton and associated particles, especially during summer and fall months. These findings could have implications for the effectiveness of enterococci as an indicator of coastal water quality, especially in particle-rich environments.

Integrated evaluation of environmental parameters influencing Vibrio occurrence in the coastal Northern Adriatic Sea (Italy) facing the Venetian lagoon

In the marine environment, the persistence and abundance of Vibrio are related to a number of environmental parameters. The influence of the different environmental variables in determining the Vibrio occurrence could be different in the specific geographic areas around the world. Moreover, oceanographic parameters are generally interdependent and should not be considered separately when their influence on bacterial presence and concentration is tested. In this study, an integrated approach was used to identify key parameters determining the abundance of Vibrio spp in marine samples from the Venetian Lagoon in Italy, which is an important area for fish farming and tourism. Multivariate techniques have been adopted to analyze the dataset: using PCA, it was shown that a relatively high proportion of the total variance in this area was mainly due to two independent variables, namely salinity and temperature. Using cluster analysis, it was possible to categorize different groups with homogeneous features as regards space ("stations") and time ("seasons") distribution, as well as to quantify the values of environmental variables and the Vibrio abundances in each category. Furthermore, integrating key environmental factors and bacterial concentration values, it was possible to identify levels of salinity and sea surface temperature which were optimal for Vibrio concentration in water, plankton, and sediment samples. The identification of key environmental variables conditioning Vibrio occurrence should facilitate ocean monitoring, making it possible to predict unexpected variations in marine microflora which determine possible public health risks in coastal areas.

Abundance of Enterococcus species, Enterococcus faecalis and Enterococcus faecium, essential indicators of fecal pollution, in river water

Enterococci such as Enterococcus faecalis and E. faecium are considered as the most suitable indicators of fecal pollution in an aquatic environment, and new methods for Enterococcus determination have been developed, namely, membrane filtration (MF) using membrane-Enterococcus indoxyl-β-D-glucoside agar (mEI) and defined substrate technology (DST) using Enterolert®. This study used PCR analysis to identify E. faecalis and E. faecium among Enterococcus strains in river water isolated using both mEI plates and Enterolert® trays. There was a significantly high correlation between MF and DST in terms of enterococcal counts for river water samples. The combined percentages of E. faecalis and E. faecium with respect to the total number of all strains obtained using mEI plates and Enterolert® trays were approximately 30 % and >30 %, respectively. Other than E. faecalis and E. faecium, a large number of Enterococcus species were unspecified in the actual urban river samples. A comparison of the predominance of E. faecalis and E. faecium found that the abundance of a species depended on the sampling river and date. E. faecium is a non-predominant species in intestinal and fecal Enterococci, and it was one of the main Enterococcus species detected in surface water.