Differentiation and identification of Shigella spp. and enteroinvasive Escherichia coli in environmental waters by a molecular method and biochemical test

Both Shigella spp. and enteroinvasive Escherichia coli (EIEC) are important human pathogens that are responsible for the majority of cases of endemic bacillary dysentery. However, they are difficult to identify and differentiate by biochemical tests or molecular methods alone. In this study, we developed a procedure to detect Shigella spp. and EIEC from environmental water samples using membrane filtration followed by nutrient broth enrichment, isolation using selective culture plates, and identification of the invasion plasmid antigen H (ipaH) gene by PCR amplification and DNA sequencing. Finally, we used a biochemical test and a serological assay to differentiate between Shigella and EIEC. Among the 93 water samples from nine reservoirs and one watershed, 76 (81.7%) water samples of culture plates had candidate colonies of Shigella and EIEC and 5 water samples were positive (5.4%) for a Shigella- and EIEC-specific polymerase chain reaction targeting the ipaH gene. Guided by the molecular method, the biochemical test, and the serological assay, 11 ipaH gene-positive isolates from 5 water samples were all identified as EIEC.     

Development of a rapid DNA extraction method and one-step nested PCR for the detection of Naegleria fowleri from the environment

Naegleria fowleri is a small free-living amoebo-flagellate found in natural and manmade thermal aquatic habitats worldwide. The organism is pathogenic to man causing fatal primary amoebic meningoencephalitis (PAM). Infection typically results from bathing in contaminated water and is usually fatal. It is, therefore, important to identify sites containing N. fowleri in the interests of preventive public health microbiology. Culture of environmental material is the conventional method for the isolation of N. fowleri but requires several days incubation and subsequent biochemical or molecular tests to confirm identification. Here, a nested one-step PCR test, in conjunction with a direct DNA extraction from water or sediment material, was developed for the rapid and reliable detection of N. fowleri from the environment. Here, the assay detected N, fowleri in 18/109 river water samples associated with a nuclear power plant in South West France and 0/10 from a similar site in the UK. Although culture of samples yielded numerous thermophilic free-living amoebae, none were N. fowleri or other thermophilic Naegleria spp. The availability of a rapid, reliable and sensitive one-step nested PCR method for the direct detection of N. fowleri from the environment may aid ecological studies and enable intervention to prevent PAM cases.     

Analysis of chromosome abnormalities in the Asian swamp eel (Monopterus albus) affected by arsenic contamination near a gold mine area

ABSTRACT

The paper reports a study of chromosome abnormalities (CA/s) in the Monopterus albus near a gold mine area compared to a non-affected area. The arsenic (As) concentrations were determined in the water, sediment and M. albus muscles. The average concentrations of As in the water and sediment samples near the gold mine were higher than allowable by Thailand’s water quality standards. The average concentrations of As in the M. albus samples were lower than the standards. The diploid chromosome number of M. albus in both areas was 2n = 24. The percentage of CA of M. albus in the gold mine area was higher than in the non-affected area. Seven types of CA were single chromatid gap (SCG), fragmentation (F), sister chromatid gap, single chromatid breaks, deletion, sister chromatid fragmentation and centric fusion. In the affected area, the most common CAs in the samples were SCG and F. The specific CA in M. albus samples was SCG on chromosome pair 1. It can be concluded that As contamination caused structural CA, but did not affect the diploid chromosome number in the Asian swamp eel from the gold mine area. The accumulation of As in M. albus has potential effects on human health in consumers of M. albus from this contaminated area.     

The evaluation of surface and wastewater genotoxicity using the Allium cepa test

Screening for mutagens in complex environmental mixtures, such as surface water or industrial wastewater, is gradually being accepted as a routine method in environmental monitoring programs. In the present work, the simplified Alliumcepa root assay was utilized to evaluate the possible cyto- and genotoxic effects of surface and wastewaters collected near the Sava River (Croatia) over a three-month monitoring period. Physicochemical characterization of the water samples included measurements of conductivity, chemical and biological oxygen demand, levels of suspended matter and salts, nitrate, nitrite, ammonium, total nitrogen and total phosphorus. Morphological modifications of the A. cepa roots, inhibition of root growth, cell division and induction of mitotic and chromosomal aberrations were observed. The most highly polluted water samples (industrial effluents) caused an inhibition of root growth of over 50%, a decrease in the mitotic index of over 40%, and a considerable increase in chromosomal aberrations compared to the control. The measured biological effects of some water samples appeared related to the physicochemical characteristics. Therefore, mutagenicity/genotoxicity assays should be included, along with conventional chemical analysis, in water quality monitoring programs. Their use would allow the quantification of mutagenic hazards in surface and wastewaters.     

Method for rapid detection of viable Escherichia coli in water using real-time NASBA

A rapid real-time NASBA method was developed for detection of Escherichia coli in water samples. In this method, a fragment of the clpB-mRNA is amplified and a specific molecular beacon probe is used to detect the amplified mRNA fragment during the NASBA reaction. The method was shown to be specific and sensitive (1 viable E. coli in 100 ml) and can be performed within 3-4 h. Different inactivation processes (starvation, heat, UV-irradiation and chlorine) were employed to study the relationship between culturability and the ability to detect E. coli using NASBA. Detection of clpB-mRNA correlated with culturability after starvation or chlorine treatment. After UV-irradiation or heat-inactivation, detection of the increase in production of clpB-mRNA in viable E. coli cells after heat-shock induction correlated with culturability. Application of the NASBA method on tap water, treated sewage and surface water samples showed that culture and NASBA yielded comparable results in these different matrices. This study demonstrates that the NASBA method has high potential as a rapid test for microbiological water quality monitoring.     

Rapid detection of Escherichia coli in water using a hand-held fluorescence detector

The quantification of pathogenic bacteria in an environmental or clinical sample commonly involves laboratory-based techniques and results are not obtained for 24-72 h after sampling. Enzymatic analysis of microbial activity in water and other environmental samples using fluorescent synthetic substrates are well-established and highly sensitive methods in addition to providing a measure of specificity towards indicative bacteria. The enzyme β-d-glucuronidase (GUD) is a specific marker for Escherichia coli and 4-methylumbelliferone-β-d-glucuronide (MUG) a sensitive substrate for determining the presence of E. coli in a sample. However, currently used procedures are laboratory-based and require bench-top fluorimeters for the measurement of fluorescence resulting from the enzyme-substrate reaction. Recent developments in electronic engineering have led to the miniaturisation of fluorescence detectors. We describe the use of a novel hand-held fluorimeter to directly analyse samples obtained from the River Thames for the presence of E. coli. The results obtained by the hand-held detector were compared with those obtained with an established fluorescent substrate assay and by quantifying microbial growth on a chromogenic medium. Both reference methods utilised filtration of water samples. The miniaturised fluorescence detector was used and incubation times reduced to 30 min making the detection system portable and rapid. The developed hand-held system reliably detected E. coli as low as 7 cfu/mL river water sample. Our study demonstrates that new hand-held fluorescence measurement technology can be applied to the rapid and convenient detection of bacteria in environmental samples. This enables rapid monitoring to be carried out on-site. The technique described is generic and it may, therefore, be used in conjunction with different fluorescent substrates which allows the assessment of various target microorganisms in biological samples.     

Investigating a single sensor ability in the characterisation of drinkable water: a pilot study

Physical and chemical characterization of Bottled water is certified on the bottle‐label, which reports the analysis performed by a qualified laboratory. All these data can be suitable treated via multidimensional evaluation and the value of certain parameters against a specific threshold, can address some of these water samples to the treatment of specific medical issues or more in general for dietary options. These thresholds are often referred only to two or three of the listed parameters. In this work, a single voltammetric sensor has been used to characterize 14 different species of bottled water, after a calibration procedure with saline matrices. The sensor has the capability to discriminate among water samples with different dry residue and it is also able to predict the parameters reported on the bottle‐label with an acceptable resolution. Considering the portability of the device and its satisfactory repeatability, the sensor could perform a water quality characterisation, synthesizing bottle‐water characteristic in a reproducible and characteristic profile. The device, when fully integrated and calibrated, can support bottled water monitoring in different steps of the production‐distribution‐utilization chain by means of real‐time measurements.     

Human and bovine adenoviruses for the detection of source-specific fecal pollution in coastal waters in Australia

In this study, the host-specificity and -sensitivity of human- and bovine-specific adenoviruses (HS-AVs and BS-AVs) were evaluated by testing wastewater/fecal samples from various animal species in Southeast, Queensland, Australia. The overall specificity and sensitivity of the HS-AVs marker were 1.0 and 0.78, respectively. These figures for the BS-AVs were 1.0 and 0.73, respectively. Twenty environmental water samples were collected during wet conditions and 20 samples were colleted during dry conditions from the Maroochy Coastal River and tested for the presence of fecal indicator bacteria (FIB), host-specific viral markers, zoonotic bacterial and protozoan pathogens using PCR/qPCR. The concentrations of FIB in water samples collected after wet conditions were generally higher compared to dry conditions. HS-AVs was detected in 20% water samples collected during wet conditions and whereas BS-AVs was detected in both wet (i.e., 10%) and dry (i.e., 10%) conditions. Both Campylobacter jejuni mapA and Salmonella invA genes detected in 10% samples collected during dry conditions. The concentrations of Salmonella invA ranged between 3.5 × 10² and 4.3 × 10² genomic copies per 500 ml of water Giardia lamblia β-giardin gene was detected only in one sample (5%) collected during the dry conditions. Weak or significant correlations were observed between FIB with viral markers and zoonotic pathogens. However, during dry conditions, no significant correlations were observed between FIB concentrations with viral markers and zoonotic pathogens. The prevalence of HS-AVs in samples collected from the study river suggests that the quality of water is affected by human fecal pollution and as well as bovine fecal pollution. The results suggest that HS-AVs and BS-AVs detection using PCR could be a useful tool for the identification of human sourced fecal pollution in coastal waters.     

Characterization of organic membrane foulants in a submerged membrane bioreactor with pre-ozonation using three-dimensional excitation-emission matrix fluorescence spectroscopy

This study focuses on organic membrane foulants in a submerged membrane bioreactor (MBR) process with pre-ozonation compared to an individual MBR using three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy. While the influent was continuously ozonated at a normal dosage, preferable organic matter removal was achieved in subsequent MBR, and trans-membrane pressure increased at a much lower rate than that of the individual MBR. EEM fluorescence spectroscopy was employed to characterize the dissolved organic matter (DOM) samples, extracellular polymeric substance (EPS) samples and membrane foulants. Four main peaks could be identified from the EEM fluorescence spectra of the DOM samples in both MBRs. Two peaks were associated with the protein-like fluorophores, and the other ones were related to the humic-like fluorophores. The results indicated that pre-ozonation decreased fluorescence intensities of all peaks in the EEM spectra of influent DOM especially for protein-like substances and caused red shifts of all fluorescence peaks to different extents. The peak intensities of the protein-like substances represented by Peak T₁ and T₂ in EPS spectra were obviously decreased as a result of pre-ozonation. Both external and internal fouling could be effectively mitigated by the pre-ozonation. The most primary component of external foulants was humic acid-like substance (Peak C) in the MBR with pre-ozonation and protein-like substance (Peak T₁) in the individual MBR, respectively. The content decrease of protein-like substances and structural change of humic-like substances were observed in external foulants from EEM fluorescence spectra due to pre-ozonation. However, it could be seen that ozonation resulted in significant reduction of intensities but little location shift of all peaks in EEM fluorescence spectra of internal foulants.     

Comparative assessment of genotoxicity of mineral water packed in polyethylene terephthalate (PET) and glass bottles

The potential migration of genotoxic compounds into mineral water stored in polyethylene terephthalate (PET) bottles was evaluated by an integrated chemical/biological approach using short-term toxicity/genotoxicity tests and chemical analysis. Six commercial brands of still and carbonated mineral water bottled in PET and in glass were stored at 40 °C for 10 days in a stove according to the standard EEC total migration test (82/711/EEC), or at room temperature in the dark. After treatment, the samples were analysed using gas-chromatography/mass spectrometry (GC/MS) to detect volatile and non-volatile compounds, the Microtox^® test to evaluate potential toxicity of the samples, and three mutagenicity tests - Tradescantia and Allium cepa micronucleus tests and the Comet assay on human leukocytes - to detect their genotoxic activity.GC/MS analysis did not detect phthalates or acetaldehyde in the water samples. The Microtox^® test found no toxic effects. Mutagenicity tests detected genotoxic properties of some samples in both PET and glass bottles. Statistical analyses showed a positive association between mineral content and mutagenicity (micronuclei in A. cepa and DNA damage in human leukocytes). No clear effect of treatment and PET bottle was found. These results suggest the absence of toxic compounds migrating from PET regardless of time and conditions of storage. In conclusion, bottle material and stove treatment were not associated with the genotoxic properties of the water; the genotoxic effects detected in bottled water may be related to the characteristics of the water (minerals and CO₂ content).     

Laboratory investigation of aluminum solubility and solid-phase properties following alum treatment of lake waters

Water samples from two southern California lakes adversely affected by internal nutrient loading were treated with a 20 mg/L dose of Al3+ in laboratory studies to examine Al solubility and solid-phase speciation over time. Alum [Al2(SO4)3 . 18 H2O] applications to water samples from Big Bear Lake and Lake Elsinore resulted in a rapid initial decrease in pH and alkalinity followed by a gradual recovery in pH over several weeks. Dissolved Al concentrations increased following treatment, reaching a maximum of 2.54 mg/L after 17 days in Lake Elsinore water and 0.91 mg/L after 48 days in Big Bear Lake water; concentrations in both waters then decreased to <0.25 mg/L after 150 days. The solid phase was periodically collected and analyzed using X-ray diffraction (XRD), differential scanning calorimetry-thermogravimetric analysis (DSC-TGA), scanning electron microscopy (SEM), and surface area analyses to investigate the nature of the reaction products and crystallinity development over time. Poorly ordered, X-ray amorphous solid phases transformed over time to relatively well-ordered gibbsite, with strong diffraction peaks at 4.8 and 4.3 A. XRD also indicated the formation of a second (possibly aluminosilicate) crystalline phase after 150 days in Lake Elsinore water. Surface areas also decreased over time as crystals reordered to form gibbsite/microcrystalline gibbsite species. DSC-TGA results suggested that the initially formed amorphous Al(OH)3 underwent transformation to >45% gibbsite. These results were supported by geochemical modeling using Visual MINTEQ, with Al solubility putatively controlled by amorphous Al(OH)3 shortly after treatment and approaching that of microcrystalline gibbsite after about 150 days. These findings indicate that Al(OH)3 formed after alum treatment undergoes significant chemical and mineralogical changes that may alter its effectiveness as a reactive barrier to phosphorus release from lake sediments.     

A voltammetric electronic tongue as tool for water quality monitoring in wastewater treatment plants

The use of a voltammetric electronic tongue as tool for the prediction of concentration levels of certain water quality parameters from influent and effluent wastewater from a Submerged Anaerobic Membrane Bioreactor pilot plant applied to domestic wastewater treatment is proposed here. The electronic tongue consists of a set of noble (Au, Pt, Rh, Ir, and Ag) and non-noble (Ni, Co and Cu) electrodes that were housed inside a stainless steel cylinder which was used as the body of the electronic tongue system. As a previous step an electrochemical study of the response of the ions sulphate, orthophosphate, acetate, bicarbonate and ammonium was carried out in water using the electrodes contained in the electronic tongue. The second part of the work was devoted to the application of the electronic tongue to the characterization of the influent and effluent waters from the wastewater treatment plant. Partial Least Squares analysis was used to obtain a correlation between the data from the tongue and the pollution parameters measured in the laboratory such as soluble chemical oxygen demand (CODs), soluble biological oxygen demand (BODs), ammonia (NH₄-N), orthophosphate (PO₄-P), Sulphate (SO₄-S), acetic acid (HAC) and alkalinity (Alk). A total of 28 and 11 samples were used in the training and the validation steps, respectively, for both influent and effluent water samples. The electronic tongue showed relatively good predictive power for the determination of BOD, COD, NH₄-N, PO₄-P, SO₄-S, and Alk.     

Rapid exposure assessment of PSII herbicides in surface water using a novel chlorophyll a fluorescence imaging assay

Recently a new Maxi-Imaging-PAM (Max-I-PAM) instrument for phytotoxicity assessment via chlorophyll fluorescence imaging was introduced. This new instrument allows rapid detection of the effects of PS II inhibiting herbicides which are high use agricultural chemicals frequently detected in surface waters in Australia and elsewhere. Several studies have applied the new instrument for detection of phytotoxicants in water using microalgae suspensions; however, these use preliminary protocols and to date no validated method is available for high throughput testing of environmental samples in 96-well plates. Here we developed and applied a new protocol allowing dose-response assessment of four samples within 2 h (8 dilutions in duplicate). The technique was found to be sensitive, with a detection limit of 2.3 ng l(-1) for the herbicide diuron when testing solid phase extracts (SPE) of 1000 ml water samples, and reproducible both between experiments (coefficient of variation (CV)=0.30) and within the 96-well plate (CV=0.06). Relative potencies were determined for four reference PS II impacting herbicides (diuron>hexazinone>atrazine>simazine). Extracts from 1000 ml environmental samples and diuron spiked ultrapure water as well as passive sampler extracts were evaluated and good agreement was found between diuron equivalent concentrations calculated from bioassay results (DEQ(IPAM)) and DEQ(CHEM) values calculated from LCMS chemical analysis of the four reference compounds in the same samples. Overall, the technique provides a valuable bioanalytical tool for rapid and inexpensive effects-based assessment of PS II impacting herbicides in environmental mixtures.     

Distribution of Asellus aquaticus and microinvertebrates in a non-chlorinated drinking water supply system--effects of pipe material and sedimentation

Danish drinking water supplies based on ground water without chlorination were investigated for the presence of the water louse, Asellus aquaticus, microinvertebrates (<2 mm) and annelida. In total, 52 water samples were collected from fire hydrants at 31 locations, and two elevated tanks (6000 and 36,000 m³) as well as one clean water tank at a waterworks (700 m³) were inspected. Several types of invertebrates from the phyla: arthropoda, annelida (worms), plathyhelminthes (flatworms) and mollusca (snails) were found. Invertebrates were found at 94% of the sampling sites in the piped system with A. aquaticus present at 55% of the sampling sites. Populations of A. aquaticus were present in the two investigated elevated tanks but not in the clean water tank at a waterworks. Both adult and juvenile A. aquaticus (length of 2-10 mm) were found in tanks as well as in pipes. A. aquaticus was found only in samples collected from two of seven investigated distribution zones (zone 1 and 2), each supplied directly by one of the two investigated elevated tanks containing A. aquaticus. Microinvertebrates were distributed throughout all zones. The distribution pattern of A. aquaticus had not changed considerably over 20 years when compared to data from samples collected in 1988-89. Centrifugal pumps have separated the distribution zones during the whole period and may have functioned as physical barriers in the distribution systems, preventing large invertebrates such as A. aquaticus to pass alive. Another factor characterising zone 1 and 2 was the presence of cast iron pipes. The frequency of A. aquaticus was significantly higher in cast iron pipes than in plastic pipes. A. aquaticus caught from plastic pipes were mainly single living specimens or dead specimens, which may have been transported passively trough by the water flow, while cast iron pipes provided an environment suitable for relatively large populations of A. aquaticus. Sediment volume for each sample was measured and our study described for the first time a clear connection between sediment volume and living A. aquaticus since living A. aquaticus were nearly only found in samples with sediment contents higher than 100 ml/m³ sample. Presence of A. aquaticus was not correlated to turbidity of the water. Measurements by ATP, heterotrophic plate counting and Colilert^® showed that the microbial quality of the water was high at all locations with or without animals. Four other large Danish drinking water supplies were additionally sampled (nine pipe samples and one elevated tank), and invertebrates were found in all systems, three of four containing A. aquaticus, indicating a nationwide occurrence.     

Development of microbial and chemical MST tools to identify the origin of the faecal pollution in bathing and shellfish harvesting waters in France

The microbiological quality of coastal or river waters can be affected by faecal pollution from human or animal sources. An efficient MST (Microbial Source Tracking) toolbox consisting of several host-specific markers would therefore be valuable for identifying the origin of the faecal pollution in the environment and thus for effective resource management and remediation. In this multidisciplinary study, after having tested some MST markers on faecal samples, we compared a selection of 17 parameters corresponding to chemical (steroid ratios, caffeine, and synthetic compounds), bacterial (host-specific Bacteroidales, Lactobacillus amylovorus and Bifidobacterium adolescentis) and viral (genotypes I-IV of F-specific bacteriophages, FRNAPH) markers on environmental water samples (n = 33; wastewater, runoff and river waters) with variable Escherichia coli concentrations. Eleven microbial and chemical parameters were finally chosen for our MST toolbox, based on their specificity for particular pollution sources represented by our samples and their detection in river waters impacted by human or animal pollution; these were: the human-specific chemical compounds caffeine, TCEP (tri(2-chloroethyl)phosphate) and benzophenone; the ratios of sitostanol/coprostanol and coprostanol/(coprostanol+24-ethylcopstanol); real-time PCR (Polymerase Chain Reaction) human-specific (HF183 and B. adolescentis), pig-specific (Pig-2-Bac and L. amylovorus) and ruminant-specific (Rum-2-Bac) markers; and human FRNAPH genogroup II.     

Transformation of the antiepileptic drug oxcarbazepine upon different water disinfection processes

Transformation of the pharmaceutical oxcarbazepine (OXC), a keto analogue of carbamazepine (CBZ) was investigated under different water disinfection processes (ozonation, chlorination and UV irradiation) to compare its persistence, toxicity and degradation pathways with those of CBZ. Analysis by LC-ion trap-MSⁿ allowed for the identification of up to thirteen transformation products (TPs). The major abundant and persistent TPs (10,11-dihydro-10,11-trans-dihydroxy-carbamazepine (DiOH-CBZ), acridine (ACIN) and 1-(2-benzaldehyde)-(1H, 3H)-quinazoline-2,4-dione (BQD)) were identical to those previously reported during water treatment of CBZ. Only one new compound arising from an intramolecular cyclisation reaction was identified during UV irradiation. OXC reacted quickly with hydroxyl radical and relatively rapidly with free chlorine while slow reaction rates were recorded in presence of ozone and upon UV irradiation. An increase of the acute toxicity of UV irradiated solutions, monitored by a Daphnia magna bioassay, was recorded, probably due to the accumulation of ACIN. The formation of ACIN is of concern due to the carcinogenic properties of this chemical. ACIN was also generated during the direct UV photo transformation of DiOH-CBZ and 10-hydroxy-10,11-dihydro-carbamazepine (OH-CBZ), two metabolites of OXC and CBZ widely detected in water resources. Analysis of tap water samples revealed the occurrence at ng/L levels of the major TPs detected under laboratory scale experiments, except ACIN.     

Microscale fluctuation assay coupled with Sep-PakR concentration as a rapid and sensitive method for screening mutagens in drinking water

A sensitive short-term mutagenicity test, the microscale fluctuation test has been coupled with a concentration method based on adsorption on Sep-Pak^R C₁₈ cartridges as a method for screening drinking water mutagens. Comparison with XAD-2 concentration method showed that Sep-Pak adsorbed 5 times higher quantity of organics but was slightly less efficient for adsorbing TOX.Microscale fluctuation test was found to be more sensitive than Ames test by testing known direct-acting mutagens and concentrates of drinking water. Samples derived from conventional treatment including chlorination from eight surface water supplies in Norway were concentrated at pH 2 by adsorption on the disposable columns. The adsorbates were tested at different doses by the microscale fluctuation assay. The mutagenic properties of drinking water samples were also related to total organic carbon (TOC), total organic halogen (TOX) and trihalomethanes (THM) concentrations. Dose-related mutagenic responses were found for all the samples with S. typhimurium TA 100 and TA98 strains without metabolic activation. Good relationship was found between mutagenicity data and TOX and THM results. The method showed to be simple, rapid and suitable for routine screening of mutagens in drinking water.     

Performance of CHROMagar™ Staph aureus and CHROMagar™ MRSA for detection of Staphylococcus aureus in seawater and beach sand - Comparison of culture, agglutination, and molecular analyses

Beach seawater and sand were analyzed for Staphylococcus aureus and methicillin resistant S. aureus (MRSA) for samples collected from Avalon, and Doheny Beach, CA. Membrane filtration followed by incubation on CHROMagar™ Staph aureus (SCA) and CHROMagar™ MRSA (C-MRSA) was used to enumerate S. aureus and MRSA, respectively. Media performance was evaluated by comparing identification via colony morphology and latex agglutination tests to PCR (clfA, 16S, and mecA genes). Due to background color and crowding, picking colonies from membrane filters and streaking for isolation were sometimes necessary. The specificity of SCA and C-MRSA was improved if colony isolates were identified by the presence of a matte halo in addition to mauve color; however routine agglutination testing of isolates did not appear warranted. Using the appearance of a colony on the membrane filter in conjunction with isolate appearance, the positive % agreement, the negative % agreement, and the % positive predictive accuracy for SCA was 84%, 95%, and 99% respectively, and for C-MRSA it was 85%, 98%, and 92%, respectively. Sensitivity and specificity of SCA and C-MRSA with membrane-filtered beach samples were optimized through identification experience, control of filter volume and incubation time, and isolation of colonies needing further identification. With optimization, SCA and C-MRSA could be used for enumeration of S. aureus and MRSA from samples of beach water and sand. For the sites studied here, the frequency of detection of S. aureus ranged from 60 to 76% and 53 to 79% for samples of beach seawater and sand, respectively. The frequency of detection of MRSA ranged from 2 to 9% and 0 to 12% for samples of seawater and sand, respectively.     

Occurrence of endocrine disrupting compounds, pharmaceuticals, and personal care products in the Han River (Seoul, South Korea)

The occurrence of 31 selected endocrine disrupting compounds (EDCs) and pharmaceuticals and personal care products (PPCPs) in Korean surface waters was investigated. The area was selected since there is a lack of information in the Seoul area on the suspected contamination of rivers by micropollutants, although over 99% of drinking water is produced from surface waters in this area that has a population of approximately 15 million inhabitants. Samples were collected from upstream/downstream and effluent-dominated creeks along the Han River, Seoul (South Korea) and analyzed by liquid chromatography with tandem mass spectrometry (LC-MS/MS) with electrospray ionization (ESI) and atmospheric pressure chemical ionization (APCI). Most target compounds were detected in both the Han River samples (63%) and the effluent-dominated creek samples (79%). Iopromide, atenolol, TCPP, TECP, musk ketone, naproxen, DEET, carbamazepine, caffeine, and benzophenone were frequently detected in both river and creek samples, although the mean concentrations in effluent-dominated creek samples (102 ng/L-3745 ng/L) were significantly higher than those in river samples (56 ng/L-1013 ng/L). However, the steroid hormones 17β-estradiol, 17α-ethynylestradiol, progesterone, and testosterone, were not detected (< 1 ng/L) in both the river and creek samples. Numerous target compounds (15) were found to be positively correlated (over 0.8) to the conventional water quality parameters (chemical oxygen demand, biochemical oxygen demand, dissolved organic carbon, and ultraviolet absorbance). Results of this study provide increasing evidence that certain EDCs and PPCPs commonly occur in the Han River as the result of wastewater outfalls.     

Inaccuracy in Legionella tests of building water systems due to sample holding time

Most Legionella culture tests are performed on building water samples that have been shipped to analytical laboratories for analysis. Significant (≥1 log₁₀ unit) changes in results were observed in 52% of held samples (6 h or longer, ambient temperature) drawn from building water systems in a 42-sample initial survey. It was not practical to use the spread plate protocol for on-site “t = 0” cultures in a larger, more diverse survey of thousands of building water systems. Two thousand four hundred twenty-one (2421) building water samples were split for on-site analysis using a field culture protocol and then also cultured after overnight shipment to the lab for analysis with the standardized spread plate method. Legionella test results from building water system samples are usually interpreted as ≥a numerical detection or action limit. Therefore, binary statistical analyses were calculated by setting t = 0 culture results to “true”. Overall in this survey, 10.4% of water samples sent to the laboratory for analysis returned either false-positive or false-negative results. The overall positive predictive value of results was poor (36%). Most (83%) false-positive results were returned from utility water systems. Most (74%) false-negative results were returned from potable water systems. These inaccuracies have serious implications in regard to interpretation and use of Legionella test results. The overall negative predictive value of results was excellent (99%) and also it was good (92%) for results from a polymerase chain reaction (PCR) assay that can be therefore used as a negative screening method.