Primary Disinfection Research Articles

MnO2-based capacitive system enhances ozone inactivation of bacteria by disrupting cell membrane

The application of ozone (O3) disinfection has been hindered by its low solubility in water and the formation of disinfection by-products (DBPs). In this study, capacitive disinfection is applied as a pre-treatment for O3 oxidation, in which manganese dioxide with a rambutan-like hollow spherical structure is used as the electrode to increase the charge density on the electrode surface. When a voltage is applied, the negative-charged microbes are attracted to the electrodes and killed by electrical interactions. The contact between microbes and capacitive electrodes leads to changes in cell permeability and burst of reactive oxygen species, thereby promoting the diffusion of O3 into the cells. After O3 penetrates the cell membrane, it can directly attack the cytoplasmic constituents, accelerating fatal and irreversible damage to pathogens. As a result, the performance of the capacitance-O3 process is proved better than the direct sum of the two individual process efficiencies. The design of capacitance-O3 system is beneficial to reduce the ozone dosage and DBPs with a broader inactivation spectrum, which is conducive to the application of ozone in primary water disinfection.

Evaluation of anti-microbial effect of Sushrutokta Vayu-Nirvishikarana yoga

Introduction: With the presence of extensive number of various microbes in the living environment, there is need to explore few sustainable and safe practices to control the ill effects of the microbes. In Indian tradition the Dhoopana (fumigation process) is well established since time immemorial and it is practiced regularly for different purposes. Many of the formulations quoted in the classics are already in practice. Acharya Sushruta, in Kalpasthana quotes the use of Vayu Nirvishikarana Yoga for Dhoopana-artha in the chikitsa of Dushita Vayu. Therefore, it is necessary to adopt safer methods like Dhoopana with the herbal formulations for the disease control. Methods: Vayu Nirvishikarana yoga comprising of 11 drugs, predominantly constitutes of volatile oils, alkaloids and tannins from the respective drugs. There are proven studies over the antimicrobial property, anti-oxidant properties of various drugs of this formulation. Results: The study was conducted to showcase the efficacy of the Dhoopana yoga in an indoor environment in terms of limiting the microbial load. The results of this work showed considerable results with sufficient scope for further studies. Conclusion: Krimighna and Vishaghna gunas of these drugs used in this formulation can be justified as explained in the classics. After evaluating the existing data about Dhoopana process and executing the study, its effectiveness becomes self-evident, but scientific approach and evidence are required to mainstream them and to establish the formulations as primary disinfection measures.

Biofilm formation and antioxidation were responsible for the increased resistance of N. eutropha to chloramination for drinking water treatment

Chloramination is an effective strategy for eliminating pathogens from drinking water and repressing their regrowth in water distribution systems. However, the inevitable release of NH4+ potentially promotes nitrification and associated ammonia-oxidizing bacteria (AOB) contamination. In this study, AOB (Nitrosomona eutropha) were isolated from environmental water and treated with two disinfection stages (chloramine disinfection and chloramine residues) to investigate the occurrence mechanisms of AOB in chloramination. The results showed that N. eutropha had considerable resistance to monochloramine compared to Escherichia coli, whose inactivation rate constant was 19.4-fold lower. The higher resistance was attributed to high levels of extracellular polymer substances (EPS) in AOB, which contribute to AOB surviving disinfection and entering the distribution system. In AOB response to the chloramine residues stage, the respiratory activity of N. eutropha remained at a high level after three days of continuous exposure to high chloramine residue concentrations (0.5–1.5 mg/L). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) suggested that the mechanism of N. eutropha tolerance involved a significantly high expression of the intracellular oxidative stress-regulating (sodB, txrA) and protein-related (NE1545, NE1546) genes. Additionally, this process enhanced EPS secretion and promoted biofilm formation. Adhesion predictions based on the XDLVO theory corroborated the trend of biofilm formation. Overall, the naturally higher resistance contributed to the survival of AOB in primary disinfection; the enhanced antioxidant response of surviving N. eutropha accompanied by biofilm formation was responsible for their increased resistance to the residual chloramines.

Emissions from Hydrogen Peroxide Disinfection and Their Interaction with Mask Surfaces.

A rise in the disinfection of spaces occurred as a result of the COVID-19 pandemic as well as an increase in people wearing facial coverings. Hydrogen peroxide was among the recommended disinfectants for use against the virus. Previous studies have investigated the emissions of hydrogen peroxide associated with the disinfection of spaces and masks; however, those studies did not focus on the emitted byproducts from these processes. Here, we simulate the disinfection of an indoor space with H2O2 while a person wearing a face mask is present in the space by using an environmental chamber with a thermal manikin wearing a face mask over its breathing zone. We injected hydrogen peroxide to disinfect the space and utilized a chemical ionization mass spectrometer (CIMS) to measure the primary disinfectant (H2O2) and a Vocus proton transfer reaction time-of-flight mass spectrometer (Vocus PTR-ToF-MS) to measure the byproducts from disinfection, comparing concentrations inside the chamber and behind the mask. Concentrations of the primary disinfectant and the byproducts inside the chamber and behind the mask remained elevated above background levels for 2-4 h after disinfection, indicating the possibility of extended exposure, especially when continuing to wear the mask. Overall, our results point toward the time-dependent impact of masks on concentrations of disinfectants and their byproducts and a need for regular mask change following exposure to high concentrations of chemical compounds.

The Minus Approach Can Redefine the Standard of Practice of Drinking Water Treatment

Chlorine-based disinfection for drinking water treatment (DWT) was one of the 20th century's great public health achievements, as it substantially reduced the risk of acute microbial waterborne disease. However, today's chlorinated drinking water is not unambiguously safe; trace levels of regulated and unregulated disinfection byproducts (DBPs), and other known, unknown, and emerging contaminants (KUECs), present chronic risks that make them essential removal targets. Because conventional chemical-based DWT processes do little to remove DBPs or KUECs, alternative approaches are needed to minimize risks by removing DBP precursors and KUECs that are ubiquitous in water supplies. We present the "Minus Approach" as a toolbox of practices and technologies to mitigate KUECs and DBPs without compromising microbiological safety. The Minus Approach reduces problem-causing chemical addition treatment (i.e., the conventional "Plus Approach") by producing biologically stable water containing pathogens at levels having negligible human health risk and substantially lower concentrations of KUECs and DBPs. Aside from ozonation, the Minus Approach avoids primary chemical-based coagulants, disinfectants, and advanced oxidation processes. The Minus Approach focuses on bank filtration, biofiltration, adsorption, and membranes to biologically and physically remove DBP precursors, KUECs, and pathogens; consequently, water purveyors can use ultraviolet light at key locations in conjunction with smaller dosages of secondary chemical disinfectants to minimize microbial regrowth in distribution systems. We describe how the Minus Approach contrasts with the conventional Plus Approach, integrates with artificial intelligence, and can ultimately improve the sustainability performance of water treatment. Finally, we consider barriers to adoption of the Minus Approach.

Removal of Dissolved Organic Matter in Drinking Water Using Active Microorganisms (EM)

Conventional treatment methods are used in the treatment of drinking water to protect human and environmental health. These methods can be named aeration to increase the amount of oxygen, precipitation, chemical treatment, filtration, chlorination for disinfection. Besides, iron and manganese removal operations are performed in places where the hardness is very high depending on the geographical location, iron and manganese removal operations are performed in cases where the iron and manganese content is high. Drinking, and drinking water treatment technologies in Turkey are generally the same. The conventional methods used are briefly described as ventilation, coagulation, flocculation, precipitation, sand filtration, and chlorination. In recent years, it has been observed that in addition to these methods, ozone has been used for primary disinfection purposes, activated carbon adsorption for advanced purification purposes, reverse osmosis studies have been performed. Conventional treatment plants are usually built when there is the use of superficial water sources. In settlements where spring or well water is used in a certain area, the water is only available by the chlorination process. The purpose of drinking water treatment is to be clear, colorless, odorless, disease-causing organism-free, free of chemicals harmful to health, and suitable for domestic use. The treatment technologies used in drinking water treatment plants vary depending on the properties that are desired to be found in purified water, as well as the properties of raw water. Physical, chemical, and biological purification, which is one of the classical methods used in the purification process, may be insufficient in the face of dissolved organic matter. This encourages us to look for new methods of combating dissolved organic matter.

Comparison of Efficacy of Diode Laser and Grape Seeds Extract as Cavity Disinfectants in Primary Teeth- an in vitro study

Purpose: Cavity disinfection is an essential procedure for success of Atraumatic restorative treatment. This study was designed to test the efficacy of diode laser and grape seeds extract as primary teeth cavity disinfectants. Methods: A total of 96 sound primary molars were divided into two groups according to the test performed (n=48); antimicrobial effect/ shear bond strength. Each group was subdivided into four subgroups according to cavity disinfectants: (n=12); group1: Control (no treatment), group 2: 2% chlorhexidine gluconates (CHX), group 3: diode laser, group 4: 5%w/v grape seed extract (GSE). Occlusal cavities were inoculated with the Streptococcus mutans (S.mutans) suspension and incubated under aerobic conditions. Dentine chips were collected and S.mutans colony forming units were counted. For shear bond strength, cylindrical glass ionomer specimens were bonded to dentine surface then loaded at tooth-restoration interface till debonding. Results: Diode laser exhibited the highest antibacterial effect. No difference was detected in mean values of shear bond strength in diode laser (5.88±1.28) and GSE (3.47±1.55) groups when compared to the negative control group (4.97±1.80). Conclusion: Diode laser system is preferred over GSE and CHX as a potent cavity disinfectant for primary teeth. GSE can be used as a natural alternative for CHX

Disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water using electrochemical flow cells: A case study in Hawaii.

This field case study reports findings on disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water carried out at an aquaculture farm and two irrigation locations in Hawaii. We used a flow cell incorporating PtRu/graphite anode and graphite cathode for the disinfection/ammonia removal from aquaculture wastewater, and a flow cell assembled with graphite plates as both anode and cathode for the disinfection of irrigation water. The removal of ammonia followed the indirect oxidation mechanism mediated by free chlorine electro-generated at the PtRu/graphite anode. Ammonia removal rate increased with the increase in NaCl concentration, applied current density, or flow rate. The disinfection of aquaculture wastewater can be readily achieved due to the presence of highly germicidal free chlorine species. The disinfection of irrigation water was realized without the addition of chemicals. The disinfection mechanism was attributed to the formation of free chlorine from the anodic oxidation of chloride ions naturally occurring in the water sources. The disinfection efficiency decreased with increasing organic matter concentration. In addition to the flow cell approach, we also successfully demonstrated the disinfection of irrigation water by adding electrolyzed NaCl solution or purging with a mixture of air and chlorine gas, both of which were generated on-site. PRACTITIONER POINTS: Field case study on disinfection/ammonia removal from aquaculture wastewater and disinfection of irrigation water was carried out in Hawaii. Electrochemical flow cell assembled with PtRu/graphite anode and graphite cathode effectively removes ammonia from aquaculture wastewater. Ammonia removal proceeds via the indirect oxidation mechanism mediated by free chlorine electro-generated at the PtRu/graphite anode. Electrochemical flow cell assembled with commercial graphite electrodes enables fast disinfection of coliform bacteria and E.coli. The primary disinfection mechanism is through chlorine species electro-generated from chloride oxidation at the graphite anode.

Modelling chlorine residual and trihalomethane profiles in water distribution systems after treatment including pre-chlorination

Accurate, efficient distribution system models predict profiles of chlorine and trihalomethane concentrations using chemical reactions. Constant coefficients defining reaction-rates are typically derived from laboratory decay-tests conducted days after sampling from a particular water treatment plant (WTP). The problem is any post-filter chlorine residual due to pre-chlorination will have reacted completely beforehand. Consequently, the derived reaction-model will not accurately represent water exiting the WTP filters. Two methods to include these missing reactions were successfully developed. They have similar accuracy but the second method is less efficient as it adds a third reactant and requires estimation of two more coefficients. Both require an additional decay-test at the WTP, commencing immediately after sampling. Due to pre-chlorination, the linear increase in total trihalomethane (TTHM) formation with increasing chlorine demand (after primary disinfection) commences at some positive TTHM concentration. The TTHM concentration measured at the laboratory must be reduced by that resulting from the post-filter residual reactions, to accurately represent TTHMs leaving the WTP. Where treatment does not involve pre-chlorination, some downstream chlorine demand does not produce TTHMs. This was accurately modelled by identifying a fraction of fast reactant as non-productive. The work extends applicability and improves accuracy of chlorine/trihalomethane modelling of distribution systems.

Metagenomic insights into dissemination of antibiotic resistance across bacterial genera in wastewater treatment

The aim of this study was to evaluate the impacts of conventional wastewater treatment processes including secondary treatment and chlorination on the removal of antibiotic resistance genes (ARGs) and antibiotic resistant bacteria (ARB), and to assess the association of ARGs with their potential hosts in each treatment process. The results showed chlorination with subinhibitory concentration (<8 mg/L) resulted in an increased ARB number in the disinfection effluent. qPCR analysis indicated secondary treatment increased relative abundance of ARGs in remaining bacteria whereas disinfection reduced the relative abundance of those genes effectively. Metagenomic analysis revealed a significant shift of dominating bacterial genera harboring ARGs. Along the treatment train, 48, 95 and 80 genera were identified to be the ARG carriers in primary effluent, secondary effluent, and disinfection effluent, respectively. It was also found that secondary treatment increased the diversity of potential ARG hosts while both secondary treatment and chlorination broadened the host range of some ARGs at the genus level, which may be attributed to the spread of antibiotic resistance across bacterial genera through horizontal transfer. This study highlights the growing concerns that wastewater treatment plants (WWTPs) may disseminate ARGs by associating this effect to specific treatment stages and by correlating ARGs with their bacterial hosts.

Classification, Uses and Environmental Implications of Disinfectants

Disinfectants are not only cleaning reagents such as soap or detergents but are hygienic materials prepared with the composition of various chemicals. Many classification routes are possible, but they are placed in two main groups, such as organic and inorganic disinfectants. The classification prevails for high level disinfectants and depends on chemical structure. In high-level disinfectants aldehydes, hydrogen peroxide, and chloride type chemicals are used. In contrast, alcohols, phenols, ammonium salts, and iodine solutions are recommended for low disinfectant applications. Soap, iodide, and alcohol solutions are the best antiseptic agents for hand and skin. Iodine-based solutions are good primary tissue and skin disinfectants. The alcohol solutions have a good inhibitory effect on many microorganisms, micro bacteria, fungi, and various viruses. These solution types are not hazardous to use as both antiseptic and surface disinfectants compared to many other chemicals.

Electrochemical disinfection of irrigation water with a graphite electrode flow cell.

In this work, we report experimental studies on the disinfection of irrigation water using a flow cell assembled with low-cost graphite plates as both anode and cathode. Natural irrigation waters collected from two irrigation locations (Reservoir 225 and Bott Well Pond) in Hawaii were used, and synthetic irrigation waters were prepared based on the chemical analysis of natural irrigation waters. The concentration of chloride was 10.2mg/L in the synthetic Reservoir 225 water and 6.9mg/L in the synthetic Bott Well pond water. Escherichia coli K12 ER2738 was selected as a model bacterium to evaluate the disinfection capability of the flow cell. Experiments performed in the synthetic irrigation waters showed that E.coli was inactivated by free chlorine species electro-generated from oxidation of chloride ions at the graphite anode. Complete removal of E.coli was achieved within 10min in the synthetic irrigation waters. The disinfection of the natural irrigation waters took about four times longer than the disinfection of the synthetic irrigation waters. This result is most likely due to the presence of organic matter (and possibly other oxidizable species) in the natural irrigation waters. PRACTITIONER POINTS: Electrochemical flow cell disinfects to 99.9% with commercial graphite electrodes. E.coli is removed in 10min from synthetic irrigation water by a flow cell. E.coli removal takes 4× longer in natural irrigation water. A minimum current density of ≥1mA/cm2 is required for disinfection. The primary disinfection mechanism is through chlorine generated from chloride ions.

Control of primary disinfection in a drinking water treatment plant based on a fuzzy inference system

Drinking water treatment plants (DWTPs) have to be efficiently managed to produce safe water at all times, independently from variations of influent water quality. Artificial Intelligence techniques like fuzzy inference systems (FIS) can help in consolidating process knowledge accumulated through years of experience and improve the consistency and resiliency of decision-making in these facilities. The objective of this study was to develop an advanced control system for choosing the combined dose of sodium hypochlorite and chlorine dioxide at the primary disinfection step of a full-scale DWTP. To accomplish this, two FISs consisting of a feed-forward and feed-back control elements were developed. The models were integrated in an environmental decision support system (EDSS) that evaluates the disinfection by-products (DBPs) formation risk and proposes actions which can be verified and applied by treatment managers. Implementation of the EDSS at a full-scale DWTP of Barcelona was positively validated 85.5 % of the times, maintaining acceptable DBPs concentrations at the effluent. The presented methodology can be used at similar surface water DWTPs for developing control strategies to manage DBPs formation.

Analysis of Biofilm-Resistance Factors in Singapore Drinking Water Distribution System

In drinking water distribution system (DWDS), biofilm offers protection of bacterial community within the extracellular polymeric substance (EPS) from outside stressors, including surrounding environment, predatory microorganisms and antibiotics. The growth of biofilm may increase cleaning and maintenance cost for the drinking water decontamination and expose high risk to human immune system. This article critically reviews current Singapore DWDS by analysing the leading and lagging performance of two stages, granulated active carbon (GAC) filtering and secondary disinfection by chloramine, which are highly relevant with the biofilm resistance. Furthermore, other extrinsic factors, such as pipe age and material, hydraulic retention time, seasonal change, primary ultraviolet disinfection, etc. are also reviewed. Finally, top-down approach to address the growth and biofilm resistance are proposed. Practices and technology methodology, e.g. good consumers’ hygiene, nutrient removal, chlorine disinfection, probiotic approach, anti-biofouling coatings are discussed with their associated challenges and opportunities.

Pre-ozonation of surface water: An effective water treatment process to reduce the risk of infection by Giardia in drinking water

Giardia is a protozoan parasite of primary concern for the drinking water industry. High contact times are required for Giardia inactivation by chlorination, while ozonation may be effective at much lower Ct products. In this study, we have assessed the occurrence of Giardia cysts in raw water, and in chlorinated or ozonated water from a drinking water treatment plant (DWTP) in Brazil, over a 16-month period. Moreover, we analyzed the effects of primary disinfection on cysts, and calculated the infection risk caused by the occurrence of Giardia cysts in raw water, chlorinated or ozonated water. Furthermore, we assessed the correlation of Giardia cysts with indicator bacteria in raw water. Data referring to concentration of Giardia cysts in raw water showed adherence to a gamma distribution at a significance level α = 0.05. The detection frequency and the mean concentration of Giardia cysts were higher in raw water (86.6%, 26 cysts∙L−1), than in chlorinated (46.1%, 15.7 cysts·L−1) or ozonated water (43.5%, 11.1 cysts·L−1). Overall, Giardia non-viable cysts were detected more frequently in ozonated water (80%) than in chlorinated water (68.2%) or raw water (37.7%). Ozonation and chlorination resulted, respectively, in ≈27.5- and ≈13- fold reduction of Giardia infection risk, when compared to the risk calculated for raw water. Total coliform and Escherichia coli proved to be suitable surrogates to predict the occurrence of Giardia cysts in raw surface water, however, the indicator bacteria may not be suitable surrogates to predict the disinfection of Giardia cysts, as no correlation was found between indicator bacteria and Giardia cysts in treated water. To our knowledge, this is the first study reporting the efficacy of chlorine and ozone at Ct products actually applied at a full-scale drinking water treatment plant against Giardia cysts naturally occurring in the source water, i.e. real situation. Ozonation has proven more efficient than chlorination against Giardia cysts in surface water. Escherichia coli proved to be suitable surrogate to predict Giardia cysts in raw surface water.

Techno-economic analysis of single disinfection units and integrated disinfection systems for sewage effluent reclamation

This study aimed to evaluate several potential candidates of single disinfection/disinfectant units and integrated disinfection systems in treating sewage effluent to obtain non-potable water, within a techno-economic analysis framework. Eight candidates of commercially available disinfection units and integrated disinfection systems were selected to be examined under the techno-economic analysis by comparison amongst the sewerage effluent. There were 4 types of treatment processes represented amongst the single disinfection units (Single): ultraviolet (UV), chlorination, microfiltration (MF), and ultrafiltration (UF). Within these processes, MF and UF both were represented twice by HVLP00010 and PVDF021 M (MF membranes); and by PVDF1001 M and PES20kDa (UF membranes). Whereas, for integrated disinfection systems (Integrated), UV disinfection and chlorination act as the primary disinfection unit, with MF/UF, Enviromulti-media (EMM) adsorption, or granular activated carbon (GAC) adsorption integrated as the pre-treatment unit. Two design capacities for water recovery - 100 m³/day (to represent a pilot-scale reproduction) and 5000 m3/day (to represent an industrial-scale reproduction) were defined to analyze and compare the cost effectiveness between single disinfection units and integrated disinfection systems chosen in this study. Amongst the studied setups, single chlorination unit and EMM-UV integrated disinfection system were the two most economical configurations to regenerate treated water for restricted applications. Whereas, the single PVDF1001 M UF membrane filtration unit was ultimately suggested as the most economic and viable technology for unrestricted water reuse purpose at both design capacities, considering the estimated cost at Malaysia currency, RM 0.50/m³ and RM 0.10/m³ for 100 m³/day and 5000 m³/day design capacity, respectively.

Genotoxicity of source, treated and distributed water from four drinking water treatment plants supplied by surface water in Sardinia, Italy

High levels of disinfection by-products (DBPs) are constantly found in drinking water distributed in Sardinia, an Italian island with a tourist vocation and critical issues related to the drinking water supply. To reduce the concentration of trihalomethanes the disinfectant in use was changed – chlorine dioxide was adopted instead of hypochlorite. However, this caused the appearance of other DBPs (e.g., chlorites) in water distributed to the population. Thus, the use of monochloramine as a secondary disinfectant (associated with chlorine dioxide as the primary disinfectant) was evaluated in four drinking water treatment plants supplied by artificial basins located in the central-northern part of Sardinia. Raw, disinfected and distributed waters were studied for genotoxicity using a battery of in vitro tests on different cells (bacteria, plant and mammalian cells) to detect different genetic endpoints (i.e., point and chromosome mutations and DNA damage). Moreover, a chemical and microbiological characterisation of water samples was performed. All samples of water distributed to the people showed mutagenic or genotoxic effects in different cells/organisms. In particular, chromosome aberrations in plant cells and DNA damage in human cells were observed. In this study, the use of chloramines associated with other disinfectants did not eliminate the mutagenicity present in the raw water and when the raw water was not mutagenic it introduced mutagenic/genotoxic substances. A careful management of drinking water is needed to reduce health hazards associated with the mutagenicity of drinking water.

PENGARUH PEMBERIAN INFUSA CARICA PAPAYA TERHADAP NYERI DISMINORE PRIMER PADA MAHASISWA

&#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; &#x0D; Primary dysmenorrhea is a pain that occursduring menstruation, without any infection of thepelvis and without abnormalities in the genitals of thereal. Ideally, disminore is natural to be experiencedby adolescents, when disminore pain is categorizedas severe it will affect daily activities. Based on thepreliminary study results, 60 female universitystudents received primary disinfectant. The aim is toanalyze the effect of giving carica papaya infusion toprimary dismalore on Midwifery student. This research uses pre experimental designwith One group Pretest posttest Design approach.Independent variables are carica papaya infusa anddependent variable is primary disminore pain. Thepopulation of this research were 60 female studentswho suffered primary disinfecting and the sampleswere 16 respondents using non-probability samplingtechnique with accidental sampling technique.Instruments used in pain scale observation sheetswere analyzed using Paired Sample T-Test statistictest. Based on the results of the research beforegiving carica papaya infusa there are 16 studentswho experienced primary disminore and after giveninfusa carica papaya all students experienceddecreased pain scale disminore. Result of statisticaltest of Paired Sample T-Test, got pain scale pre andpost result got result p value &lt;a or (0,000 &lt;0,05) soHa accepted. This suggests that there is an effect ofdisminary pain scale between before and aftertreatment of carica papaya infusa. It is expected that female students whoexperience disminore pain to get used tononpharmacology therapy to reduce pain like one ofthem by drinking carica papaya infusa.&#x0D;

Carbapenemase-producing Enterobacteriaceae and Aeromonas spp. present in wastewater treatment plant effluent and nearby surface waters in the US.

Carbapenemase-producing bacteria (CPB) are rare, multidrug resistant organisms most commonly associated with hospitalized patients. Metropolitan wastewater treatment plants (WWTP) treat wastewater from large geographic areas which include hospitals and may serve as epidemiologic reservoirs for the maintenance or expansion of CPB that originate from hospitals and are ultimately discharged in treated effluent. However, little is known about the potential impact of these WWTP CPB on the local surface water and their risk to the public health. In addition, CPB that are present in surface water may ultimately disseminate to intensively-managed animal agriculture facilities where there is potential for amplification by extended-spectrum cephalosporins. To better understand the role of WWTPs in the dissemination of CPB in surface waters, we obtained samples of treated effluent, and both upstream and downstream nearby surface water from 50 WWTPs throughout the US. A total of 30 CPB with clinically-relevant genotypes were recovered from 15 WWTPs (30%) of which 13 (50%) serviced large metropolitan areas and 2 (8.3%) represented small rural populations (P < 0.05). Recovery of CPB was lowest among WWTPs that utilized ultraviolet radiation for primary disinfection (12%), and higher (P = 0.11) for WWTPs that used chlorination (42%) or that did not utilize disinfection (50%). We did not detect a difference in CPB recovery by sampling site, although fewer CPB were detected in upstream (8%) compared to effluent (20%) and downstream (18%) samples. Our results indicate that WWTP effluent and nearby surface waters in the US are routinely contaminated with CPB with clinically important genotypes including those producing Klebsiella pneumoniae carbapenemase (KPC) and New Delhi metallo-beta-lactamase (NDM). This is a concern for both public health and animal agriculture because introduction of CPB into intensively managed livestock populations could lead to their amplification and foodborne dissemination.

355 Establishing Ovine Model of Burn Wounds Grafted with Cadaver Skin

Shortage in autograft skin to cover burn wounds require a frequent use of cadaver skin as a temporary cover. Cadaver skin graft prevents infection and dehydration and prepares the wound bed for subsequent skin autograft or application of autologous tissue engineered skin constructs. The aim of this study was to establish an ovine model of burn wound healing using ovine cadaver skin. Quality and efficacy of fresh and frozen cadaver skins were evaluated comparing to skin autograph. Cadaver skin samples were harvested from sheep used for different studies at necropsy. The cadaver skin preparation process consisted of 4 steps: preparation for recovery by wool shaving and applying primary disinfection, collection, disinfection, and cryopreservation. First, to fully characterize fresh and frozen cadaver skin, the harvested skin was evaluated based on microbial screening, skin thickness, viability, and cell proliferation in in vitrocondition. The froze skin was evaluated after 10 and 40 days of freezing. Then we compared acceptance/rejection of autograft, freshly prepared and frozen cadaver skins overlaid onto burn ovine wounds. Full thickness skin burns (5X5cm) were induced in sheep dorsum. After 24 hrs, burned skins were excised and wounds were allocated to following groups: 1) Fresh ovine cadaver skin, 2) Frozen cadaver skin, 3) Autograft, 4) No cover. Pictorial record and skin biopsies were collected 7, 14 and 20 days after grafting cadaver skin. Prepared cadaver (fresh & frozen) skins were negative for bacterial growth. Thethickness was comparable between the freshly prepared and frozen skins for 10 or 40 days. Significant reduction in skin viability was detected in frozen skin after freezing for 40 days. Histological analysis of burn wounds biopsies showed that skin autograft maintains normal skin structure at different time points. However, fresh cadaver skin graft showed signs (vacuoles in epidermis) of rejection starting from day 7 as evidenced by microscopic analysis. At day 14, the epidermis was mostly rejected, and the rejection was completed by day 20. Histologically, signs of immunoreaction and presence of many immune cells were noted. Frozen Cadaver skin followed the same pattern of fresh cadaver skin rejection rate. Viability of fresh frozen cadaver skin before grafting was significantly higher vs. frozen (40 days). However, on average both fresh or frozen ovine cadaver skins were rejected within 8.5 days that mimics rejection time in humans (~8.4 days), suggesting that ovine model of burn wound grafted with cadaver skin can successfully be used in burn wound research mimicking clinical scenario. Establishing a clinically relevant ovine model for burn wounds grafted with cadaver skin is a potential contribution to the burn research.