Kelly R Bright
- Associate Research Professor
- Associate Research Professor, Public Health
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- Alum, A., Villegas, E. N., Keely, S. P., Bright, K. R., Sifuentes, L. Y., & Abbaszadegan, M. (2016). Chapter 3.1.6. Detection of Protozoa in Surface and Finished Waters. In Manual of Environmental Microbiology, 4th Edition(pp 3.1.6-1 – 3.1.6-25). Washington, DC: ASM Press. doi:https://doi.org/10.1128/9781555818821.ch3.1.6
- Bright, K. R., & Gilling, D. H. (2016). Chapter 16. Natural virucidal compounds in foods. In Viruses in Foods, 2nd Edition(pp 449-469). New York, NY: Springer Science. doi:https:/doi.org/10.1007/978-3-319-30723-7
- Yepiz-Gomez, M. S., Bright, K. R., & Gerba, C. P. (2010). Implicación de los artículos de limpieza en la contaminación cruzada de áreas en contacto con alimentos.. In Nuevas tendencias en ciencia y tecnología de alimentos: Tópicos selectos. Hermosillo, Sonora, Mexico: Universidad de Sonora.
- Gerba, C. P., Blair, B. L., Sarkar, P., Bright, K. R., MacLean, R. C., & Marciano-Cabral, F. (2009). Chapter 19 - Occurrence and control of Naegleria fowleri in drinking water wells. In Giardia and Cryptosporidium: From Molecules to Disease.(pp 238-247). Cambridge, MA: CAB International.More infoNaegleria fowleri is a water-based protozoan found naturally in soil and warm waters. Thedeaths of two children due to N. fowleri in the Phoenix, AZ, metropolitan area occurredin 2002, and the drinking water obtained from groundwater was found to be the sourceof the exposure. A survey was conducted of municipal drinking water wells in central andsouthern Arizona. N. fowleri was identified in 11 of 143 wells tested. The calculated Ct(chlorine concentration × time) for N. fowleri cysts by free chlorine was 31 for a 99%reduction at room temperature, pH 7.5 and trophozoites 6. Chlorination can be used tocontrol N. fowleri transmission via drinking water with appropriate guidance related toproper dosages and contact times.
- Abd-Elmaksoud, S., Castro-Del Campo, N., Gerba, C. P., Pepper, I. L., & Bright, K. R. (2019). Comparative Assessment of BGM and PLC/PRF/5 Cell Lines for Enteric Virus Detection in Biosolids. FOOD AND ENVIRONMENTAL VIROLOGY, 11(1), 32-39. doi:https://doi.org/10.1007/s12560-019-09366-4More infoThe buffalo green monkey (BGM) cell line is required for the detection of enteric viruses in biosolids through a total culturable viral assay (TCVA) by the United States Environmental Protection Agency. In the present study, BGM and PLC/PRF/5 cell lines were evaluated for TCVA and for their use in determining the incidence of adenoviruses and enteroviruses in raw sludge and Class B biosolids. Six raw sludge and 17 Class B biosolid samples were collected from 13 wastewater treatment plants from seven U.S. states. Samples were processed via organic flocculation and concentrate volumes equivalent to 4 g total solids were assayed on BGM and PLC/PRF/5 cells. Cell monolayers were observed for cytopathic effect (CPE) after two 14-days passages. Cell lysates were tested for the presence of adenoviruses and enteroviruses by PCR or RT-PCR. The PLC/PRF/5 cells detected more culturable viruses than the BGM cells by CPE (73.9% vs. 56.5%, respectively). 52% of the samples were positive for CPE using both cell lines. No viruses were detected in either cell line by PCR in flasks in which CPE was not observed. No adenoviruses were detected in 13 CPE-positive samples from BGM lysates. In contrast, of the 17 samples exhibiting CPE on PLC/PRF/5 cells, 14 were positive for adenoviruses (82.4%). In conclusion, PLC/PRF/5 cells were superior for the detection of adenoviruses in both raw sludge and Class B biosolids. Thus, the use of BGM cells alone for TCVA may underestimate the viral concentration in sludge/biosolid samples.
- Gilling, D. H., Ravishankar, S., & Bright, K. R. (2019). Antimicrobial efficacy of plant essential oils and extracts against Escherichia coli. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A - TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, 54(7), 608-616. doi:https://doi.org/10.1080/10934529.2019.1574153More infoThe efficacies of 11 plant-derived antimicrobials were evaluated against Escherichia coli in vitro in solution at room temperature. These included lemongrass, cinnamon, and oregano essential oils and their active components (citral, cinnamaldehyde, and carvacrol, respectively). Allspice and clove bud oils and olive, green tea, and grape seed extracts were also studied. The efficacies of the antimicrobials were both concentration- and exposure time-dependent. The essential oils and their active components demonstrated statistically significant >5.0-log10 reductions within 1-10 min. The plant extracts were less effective; green tea and grape seed extracts required 24 h before significant reductions were observed (1.93-log10 and 5.05-log10, respectively). Nevertheless, olive extract exhibited a reduction of ∼5-log10 within 30 min. Most of these plant-derived compounds exhibited strong bactericidal activity and can potentially be applied as alternatives to chemicals for foods/food contact surfaces since they are generally recognized as safe (GRAS) for human consumption. They may also be useful in applications in which other antimicrobials have reduced efficacy (e.g., in the presence of organics) or used with sensitive populations that are unable to tolerate exposure to harsher chemicals (e.g., elderly care facilities). These compounds could be used alone, in combination, or with fast-acting antimicrobials to provide a long-lasting residual.
- Rock, C. M., Brassill, N., Dery, J. L., Carr, D., Mclain, J. E., Bright, K. R., & Gerba, C. P. (2019). Review of water quality criteria for water reuse and risk-based implications for irrigated produce under the FDA Food Safety Modernization Act, produce safety rule. ENVIRONMENTAL RESEARCH, 172, 616-629. doi:https://doi.org/10.1016/j.envres.2018.12.050More infoQuestions related to the safety of alternative water sources, such as recycled water or reclaimed water (including grey water, produced water, return flows, and recycled wastewater), for produce production have been largely un-explored at the detail warranted for protection of public health. Additionally, recent outbreaks of Escherichia coli (E. coli) in fresh produce, in which agricultural water was suspected as the source, coupled with heightened media coverage, have elevated fruit and vegetable safety into the forefront of public attention. Exacerbating these concerns, new Federal regulations released by the U.S. Food and Drug Administration (FDA) as part of implementation of the FDA Food Safety Modernization Act (FSMA), require testing of agricultural water quality for generic E. coli. Here, we present a review of water quality criteria - including surface water, groundwater recreational water, and water reuse - in an attempt to better understand implications of new FDA regulations on irrigated produce. In addition, a Quantitative Microbial Risk Assessment (QMRA) was conducted to estimate risks from pathogen contamination of food crops eaten fresh under the context of FDA regulations to provide perspective on current water reuse regulations across the country. Results indicate that irrigation water containing 126 CFU/100 mL of E. coli correspond to a risk of GI illness (diarrhea) of 9 cases in 100,000,000 persons (a 0.000009% risk) for subsurface irrigation, 1.1 cases in 100,000 persons (a 0.0011% risk) for furrow irrigation, and 1.1 cases in 1000 persons (a 0.11% risk) for sprinkler irrigation of lettuce. In comparison to metrics in states that currently regulate the use of recycled water for irrigation of food crops eaten fresh, the FDA FSMA water quality metrics are less stringent and therefore the use of recycled water presents a reduced risk to consumers than the FDA regulations. These findings, while limited to a one-time exposure event of lettuce irrigated with water meeting FSMA water quality regulations, highlight the need for additional assessments to determine if the scientific-basis of the regulation is protective of public health.
- Sicairos-Ruelas, E. E., Gerba, C. P., & Bright, K. R. (2019). Efficacy of copper and silver as residual disinfectants in drinking water. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A - TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, 54(2), 146-155. doi:https://doi.org./10.1080/10934529.2018.1535160More infoContamination events and biofilms can decrease the amount of free chlorine available in drinking water systems. The efficacy of 100 μg/L silver and 400 μg/L copper, individually and combined, were evaluated as secondary, longer-lasting residual disinfectants against Salmonella enterica serovar Typhimurium, Escherichia coli, Listeria monocytogenes, and Mycobacterium fortuitum at 24 °C and 4 °C. A >5.0-log10 reduction was observed in E. coli and L. monocytogenes after three hours and S. Typhimurium following seven hours of exposure to silver. M. fortuitum was the most resistant species to silver (1.11-log10 after seven hours). Copper did not significantly reduce S. Typhimurium and E. coli at 24 °C; ≥2.80-log10 reductions were observed in the Gram-positive L. monocytogenes and M. fortuitum. Longer exposure times were required at 4 °C to achieve significant reductions in all species. A synergistic effect was observed when silver and copper were combined at 24 °C. In addition, silver was not affected by the presence of organic matter at concentrations that completely inhibited 0.2 mg/L chlorine. The results of this study suggest that combinations of silver and copper show promise as secondary residual disinfectants. They may also be used in conjunction with low chlorine levels or other disinfectants to provide additional, long-lasting residuals in distribution systems.
- Lothrop, N., Bright, K. R., Sexton, J. D., Pearce-Walker, J., Reynolds, K. A., & Verhougstraete, M. (2018). Optimal strategies for monitoring irrigation water quality. AGRICULTURAL WATER MANAGEMENT, 199, 86-92. doi:https://doi.org/10.1016/j.agwat.2017.12.018More infoThe quality of irrigation water drawn from surface water sources varies greatly. This is particularly true for waters that are subject to intermittent contamination events such as runoff from rainfall or direct entry of livestock upstream of use. Such pollution in irrigation systems increases the risk of food crop contamination and require adoption of best monitoring practices. Therefore, this study aimed to define optimal strategies for monitoring irrigation water quality. Following the analysis of 1357 irrigation water samples for Escherichia coli, total coliforms, and physical and chemical parameters, the following key irrigation water collection approaches are suggested: 1) explore up to 950 m upstream to ensure no major contamination or outfalls exists; 2) collect samples before 12:00 p.m. local time; 3) collect samples at the surface of the water at any point across the canal where safe access is available; and 4) composite five samples and perform a single E. coli assay. These recommendations comprehensively consider the results as well as sampling costs, personnel effort, and current scientific knowledge of water quality characterization. These strategies will help to better characterize risks from microbial pathogen contamination in irrigation waters in the Southwest United States and aid in risk reduction practices for agricultural water use in regions with similar water quality, climate, and canal construction.
- Bright, K. R., & Gerba, C. P. (2017). Review: Occurrence of the pathogenic amoeba Naegleria fowleri in groundwater. HYDROGEOLOGY JOURNAL, 25(4), 953-958. doi:https://doi.org/10.1007/s10040-017-1582-4More infoNaegleria fowleri is a thermophilic free-livingamoeba found worldwide in soils and warm freshwater. It isthe causative agent of primary amebic meningoencephalitis, anearly always fatal disease afflicting mainly children andyoung adults. Humans are exposed to the organism via swimming,bathing, or other recreational activity during which wateris forcefully inhaled into the upper nasal passages.Although many studies have looked at the occurrence ofN. fowleri in surface waters, limited information is availableregarding its occurrence in groundwater and geothermallyheated natural waters such as hot springs. This paper reviewsthe current literature related to the occurrence of N. fowleri inthese waters and the methods employed for its detection. Casereports of potential groundwater exposures are also included.Despite increased interest in N. fowleri in recent years due towell-publicized cases linked to drinking water, many questionsstill remain unanswered. For instance, why the organismpersists in some water sources and not in others is not wellunderstood. The role of biofilms in groundwater wells andplumbing in individual buildings, and the potential forwarming due to climate change to expand the occurrence ofthe organism into new regions, are still unclear. Additionalresearch is needed to address these questions in order to betterunderstand the ecology of N. fowleri and the conditions thatresult in greater risks to bathers.
- Gilling, D. H., Kitajima, M., Torrey, J. R., & Bright, K. R. (2014). Antiviral efficacy and mechanisms of action of oregano essential oil and its primary component carvacrol against murine norovirus. JOURNAL OF APPLIED MICROBIOLOGY, 116(5), 1149-63. doi:https://doi.org/10.1111/jam.12453More infoAIMS: To investigate the antiviral efficacy of oregano oil and its primary active component, carvacrol, against the nonenveloped murine norovirus (MNV), a human norovirus surrogate.METHODS AND RESULTS: Along with an observed loss in cell culture infectivity, the antiviral mechanisms of action were determined in side-by-side experiments including a cell-binding assay, an RNase I protection assay and transmission electron microscopy (TEM). Both antimicrobials produced statistically significant reductions (P ≤ 0·05) in virus infectivity within 15 min of exposure (c. 1·0-log10). Despite this, the MNV infectivity remained stable with increasing time exposure to oregano oil (1·07-log10 after 24 h), while carvacrol was far more effective, producing up to 3·87-log10 reductions within 1 h. Based on the RNase I protection assay, both antimicrobials appeared to act directly upon the virus capsid and subsequently the RNA. Under TEM, the capsids enlarged from ≤35 nm in diameter to up to 75 nm following treatment with oregano oil and up to 800 nm with carvacrol; with greater expansion, capsid disintegration could be observed. Virus adsorption to host cells did not appear to be affected by either antimicrobial.CONCLUSIONS: Our results demonstrate that carvacrol is effective in inactivating MNV within 1 h of exposure by acting directly on the viral capsid and subsequently the RNA.SIGNIFICANCE AND IMPACT OF THE STUDY: This study provides novel findings on the antiviral properties of oregano oil and carvacrol against MNV and demonstrates the potential of carvacrol as a natural food and surface (fomite) sanitizer to control human norovirus.
- Gilling, D. H., Kitajima, M., Torrey, J. R., & Bright, K. R. (2014). Mechanisms of antiviral action of plant antimicrobials against murine norovirus. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 80(16), 4898-910. doi:https://doi.org/10.1128/AEM.00402-14More infoNumerous plant compounds have antibacterial or antiviral properties; however, limited research has been conducted with nonenveloped viruses. The efficacies of allspice oil, lemongrass oil, and citral were evaluated against the nonenveloped murine norovirus (MNV), a human norovirus surrogate. The antiviral mechanisms of action were also examined using an RNase I protection assay, a host cell binding assay, and transmission electron microscopy. All three antimicrobials produced significant reductions (P ≤ 0.05) in viral infectivity within 6 h of exposure (0.90 log10 to 1.88 log10). After 24 h, the reductions were 2.74, 3.00, and 3.41 log10 for lemongrass oil, citral, and allspice oil, respectively. The antiviral effect of allspice oil was both time and concentration dependent; the effects of lemongrass oil and citral were time dependent. Based on the RNase I assay, allspice oil appeared to act directly upon the viral capsid and RNA. The capsids enlarged from ≤ 35 nm to up to 75 nm following treatment. MNV adsorption to host cells was not significantly affected. Alternatively, the capsid remained intact following exposure to lemongrass oil and citral, which appeared to coat the capsid, causing nonspecific and nonproductive binding to host cells that did not lead to successful infection. Such contrasting effects between allspice oil and both lemongrass oil and citral suggest that though different plant compounds may yield similar reductions in virus infectivity, the mechanisms of inactivation may be highly varied and specific to the antimicrobial. This study demonstrates the antiviral properties of allspice oil, lemongrass oil, and citral against MNV and thus indicates their potential as natural food and surface sanitizers to control noroviruses.
- Sifuentes, L. Y., Choate, B. L., Gerba, C. P., & Bright, K. R. (2014). The occurrence of Naegleria fowleri in recreational waters in Arizona. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A - TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, 49(11), 1322-1330. doi:https://doi.org/10.1080/10934529.2014.910342More infoNaegleria fowleri is a free-living amoeba found in waters in warmer regions that causes primary amoebic meningoencephalitis, a rare but almost universally fatal disease. The goal of this project was to assess the occurrence of N. fowleri and other thermophilic amoebae in 33 recreational surface waters across Arizona to determine if their presence could be correlated with seasonal or other environmental factors. First, 1-L grab samples were collected over two years and analyzed using polymerase chain reaction and amoebae viability. Seasonality was observed, with N. fowleri and thermophilic amoebae (20% and 30%, respectively) being detected more often in the winter and spring combined than in the summer and fall combined (7.9% and 9.5%, respectively). The spring and fall both had an average temperature of 18°C, yet had different occurrence data (18.2% versus 5.9% for N. fowleri, respectively; 27.3% versus 0% for viable amoebae, respectively). These results are in stark contrast to previous studies in which N. fowleri has been found almost exclusively during warmer months. Over the two-year study, N. fowleri was detected in six and thermophilic amoebae in eight of the 33 recreational water bodies. Five of these were lakes near Phoenix that tested positive for N. fowleri and thermophilic amoebae over multiple seasons. These lakes differed significantly (P ≤ 0.05) from the other 28 surface waters, with a lower average temperature in the spring, a higher temperature in the fall, a higher pH and turbidity in the summer, and a lower electro-conductivity in the spring. They also had lower Escherichia coli and heterotrophic bacteria levels during colder months. Future N. fowleri monitoring in Arizona should focus on these five lakes to further elucidate the factors that contribute to the low occurrence of this amoeba in the summer or which might explain why these lakes appear to be reservoirs for the organism.
- Ajibode, O. M., Rock, C. M., Bright, K. R., Mclain, J. E., Gerba, C. P., & Pepper, I. L. (2013). Influence of residence time of reclaimed water within distribution systems on water quality. JOURNAL OF WATER REUSE AND DESALINATION, 3(3), 185-196. doi:https:/doi.org/10.2166/wrd.2013.088More infoThe influence of residence time of reclaimed water within water distribution systems on microbial water quality was evaluated in two wastewater reclamation facilities in southern Arizona over a 15-month period. These utilities differed in age, geographic location, means of treatment, and disinfection (i.e. UV versus chlorine). At both facilities, samples were collected from the point of compliance (POC) directly after disinfection, and at discrete locations with increasing distance from the POC. Following entry into reclaimed water distribution systems, overall microbial water quality decreased rapidly due to microbial regrowth. However, following such regrowth, microbial concentrations remained relatively constant. Water-based opportunistic pathogens (Legionella, Mycobacterium, and Aeromonas) were frequently detected in both reclaimed water systems. In contrast, waterborne indicators such as Escherichia coli and Enterococcus were rarely detected, and only at low concentrations. These dates suggest the need for new indicators of water-based pathogens to be developed. Rechlorination in one of the distribution systems only reduced the concentration of bacteria temporarily due to rapid dissipation of chlorine, and subsequent regrowth of both water-based pathogens and indicators. Amoebic activity was detected in approximately one-third of all samples tested from both utilities, but was not correlated with either water-based pathogens or indicators.
- Iker, B. C., Bright, K. R., Pepper, I. L., Gerba, C. P., & Kitajima, M. (2013). Evaluation of commercial kits for the extraction and purification of viral nucleic acids from environmental and fecal samples. JOURNAL OF VIROLOGICAL METHODS, 191(1), 24-30. doi:https://doi.org/10.1016/j.jviromet.2013.03.011More infoThe extraction and purification of nucleic acids is a critical step in the molecular detection of enteric viruses from environmental or fecal samples. In the present study, the performance of three commercially available kits was assessed: the MO BIO PowerViral Environmental DNA/RNA Isolation kit, the Qiagen QIAamp Viral RNA Mini kit, and the Zymo ZR Virus DNA/RNA Extraction kit. Viral particles of adenovirus 2 (AdV), murine norovirus (MNV), and poliovirus type 1 (PV1) were spiked in molecular grade water and three different types of sample matrices (i.e., biosolids, feces, and surface water concentrates), extracted with the kits, and the yields of the nucleic acids were determined by quantitative PCR (qPCR). The MO BIO kit performed the best with the biosolids, which were considered to contain the highest level of inhibitors and provided the most consistent detection of spiked virus from all of the samples. A qPCR inhibition test using an internal control plasmid DNA and a nucleic acid purity test using an absorbance at 230 nm for the nucleic acid extracts demonstrated that the MO BIO kit was able to remove qPCR inhibitors more effectively than the Qiagen and Zymo kits. These results suggest that the MO BIO kit is appropriate for the extraction and purification of viral nucleic acids from environmental and clinical samples that contain high levels of inhibitors.
- Soto-Beltran, M., Ikner, L. A., & Bright, K. R. (2013). Effectiveness of poliovirus concentration and recovery from treated wastewater by two electropositive filter methods. FOOD AND ENVIRONMENTAL VIROLOGY, 5(2), 91-6. doi:https://doi.org/10.1007/s12560-013-9104-6More infoEnteric viruses are often present in low numbers in various water matrices. Virus sampling therefore involves multiple concentration steps to condense large samples down to small volumes for detection by cell culture or molecular assays. The NanoCeram® Virus Sampler has been demonstrated to be effective for the recovery of viruses from tap water, surface waters, and seawater. The goal of this study was to evaluate a new method using NanoCeram® filters for the recovery of poliovirus 1 (PV-1) from treated wastewater. Activated sludge effluent samples were spiked with PV-1 and concentrated in side-by-side tests by two methods: (1) NanoCeram® filtration, elution with sodium polyphosphate buffer, secondary concentration via centrifugal ultrafiltration; and (2) 1MDS filtration, elution with beef extract, secondary concentration via organic flocculation. The virus retention and elution efficiencies did not differ significantly between the two methods. In contrast, the secondary concentrate volume was smaller for the NanoCeram® method (8.4 vs. 30 mL) and the secondary concentration efficiencies were different between the two methods with 98 % for centrifugal ultrafiltration (NanoCeram® and 45 % for organic flocculation (1MDS). The overall method efficiencies were significantly different (P ≤ 0.05) with the NanoCeram® method yielding a 57 % and the 1MDS a 23 % virus recovery. In addition, there appeared to be less interference with viral detection via polymerase chain reaction with the NanoCeram® concentrates. This NanoCeram® method therefore is able to efficiently recover PV-1 from large volumes of wastewater and may serve as an inexpensive alternative to the standard 1MDS filter method for such applications.
- Yépiz-Gómez, M. S., Gerba, C. P., & Bright, K. R. (2013). Survival of Respiratory Viruses on Fresh Produce. FOOD AND ENVIRONMENTAL VIROLOGY, 5(3), 150-156. doi:https://doi.org/10.1007/s12560-013-9114-4More infoIn addition to enteric viruses of fecal origin, emerging zoonotic viruses such as respiratory coronaviruses and influenza viruses may potentially be transmitted via contaminated foods. The goal of this study was to determine the recovery efficiencies and the survival of two respiratory viruses, namely, adenovirus 2 (Ad2) and coronavirus 229E (CoV229E), on fresh produce in comparison to the enteric poliovirus 1 (PV1). Adenovirus was recovered with efficiencies of 56.5, 31.8, and 34.8 % from lettuce, strawberries, and raspberries, respectively. Coronavirus was recovered from lettuce with an efficiency of 19.6 % yet could not be recovered from strawberries. Poliovirus was recovered with efficiencies of 76.7 % from lettuce, but only 0.06 % from strawberries. For comparison purposes, the survival of Ad2, CoV229E, and PV1 was determined for periods up to 10 days on produce. The enteric PV1 survived better than both respiratory viruses on lettuce and strawberries, with only ≤1.03 log reductions after 10 days of storage at 4 °C compared to CoV229E not being recovered after 4 days on lettuce and reductions of 1.97 log and 2.38 log of Ad2 on lettuce and strawberries, respectively, after 10 days. Nevertheless, these respiratory viruses were able to survive for at least several days on produce. There is therefore the potential for transfer to the hands and subsequently to the mucosa via rubbing the eyes or nose. In addition, some respiratory coronaviruses (e.g., severe acute respiratory syndrome coronavirus) and adenoviruses are also capable of replication in the gut and there is thus some potential for acquisition through the consumption of contaminated produce.
- Ikner, L. A., Gerba, C. P., & Bright, K. R. (2012). Concentration and recovery of viruses from water: a comprehensive review. FOOD AND ENVIRONMENTAL VIROLOGY, 4(2), 41-67. doi:https://doi.org/10.1007/s12560-012-9080-2More infoEnteric viruses are a cause of waterborne disease worldwide, and low numbers in drinking water can present a significant risk of infection. Because the numbers are often quite low, large volumes (100-1,000 L) of water are usually processed. The VIRADEL method using microporous filters is most commonly used today for this purpose. Negatively charged filters require the addition of multivalent salts and acidification of the water sample to effect virus adsorption, which can make large-volume sampling difficult. Positively charged filters require no preconditioning of samples, and are able to concentrate viruses from water over a greater pH range than electronegative filters. The most widely used electropositive filter is the Virosorb 1MDS; however, the Environmental Protection Agency has added the positively charged NanoCeram filters to their proposed Method 1615. Ultrafilters concentrate viruses based on size exclusion rather than electrokinetics, but are impractical for field sampling or processing of turbid water. Elution (recovery) of viruses from filters following concentration is performed with organic (e.g., beef extract) or inorganic solutions (e.g., sodium polyphosphates). Eluates are then reconcentrated to decrease the sample volume to enhance detection methods (e.g., cell culture infectivity assays and molecular detection techniques). While the majority of available filters have demonstrated high virus retention efficiencies, the methods to elute and reconcentrate viruses have met with varying degrees of success due to the biological variability of viruses present in water.
- Reynolds, K. A., Boone, S., Bright, K. R., & Gerba, C. P. (2012). Occurrence of household mold and efficacy of sodium hypochlorite disinfectant. JOURNAL OF OCCUPATIONAL AND ENVIRONMENTAL HYGIENE, 9(11), 663-9. doi:https://doi.org/10.1080/15459624.2012.724650More infoThe occurrence and distribution of mold on household surfaces and the efficacy of bleach-based (sodium hypochlorite, NaOCl) disinfectants on mold viability and allergenicity was documented. Household microenvironments prone to increased moisture were specifically targeted. Using the sticky tape method, 1330 samples were collected from non-porous indoor surfaces of 160 homes across the United States, and analyzed for mold. Homes were randomly selected and recruited via phone interviews. Culture and immunoassays were used to measure the viability and reduction of allergenic properties of Aspergillus fumigatus following 2.4% NaOCl treatment. All homes and 72.9% of surfaces tested positive for mold. Windowsills were the most frequently contaminated site (87.5%) and Cladosporium the most commonly identified mold (31.0%). Five-minute exposures to 2.4% NaOCl resulted in a >3 to >6-log₁₀ reduction of culturable mold counts in controlled laboratory studies. Organisms were nonculturable after 5- and 10-min contact times on non-porous and porous ceramic carriers, respectively, and A. fumigatus spore-eluted allergen levels were reduced by an average 95.8% in 30 sec, as indicated by immunoassay. All homes are contaminated with some level of mold, and regrowth is likely in moisture-prone microenvironments. The use of low concentrations (2.4%) of NaOCl for the reduction of culturable indoor mold and related allergens is effective and recommended.
- Torres-Urquidy, O., & Bright, K. R. (2012). Efficacy of multiple metals against copper-resistant bacterial strains. JOURNAL OF APPLIED MICROBIOLOGY, 112(4), 695-704. doi:https://doi.org/10.1111/j.1365-2672.2012.05245.xMore infoAims: The antibacterial efficacy of zeolites containing copper (Cu) or silver(Ag) ions or a combination was assessed against several reported copper-resistant(CuR) bacterial strains.Methods and Results: Comparison strains were obtained from the AmericanType Culture Collection that had no documented metal resistance. Reductionsin bacterial populations were determined after exposure time intervals of 3, 6and 24 h. All three CuR strains of Salmonella enterica exhibited resistance toCu, Ag and Cu ⁄ Ag after three and 6 h of exposure. Both the CuR and comparisonstrain of Enterococcus faecium were resistant to both metals and the metalcombination. CuR Pseudomonas putida was significantly reduced by all zeoliteswithin 3 h. The CuR Escherichia coli strain was more sensitive to Cu, but moreresistant to Ag than the comparison strain; however, significant reductionswere achieved within 3 h with both Cu and Cu ⁄ Ag, and within 24 h with Ag.Conclusions: Some strains with reported resistance to Cu were also resistant toAg, suggestive of a shared resistance mechanism such as an indiscriminate Cuefflux pump. Ent. faecium appears to have innate resistance to both metals. Ingeneral, Ent. faecium was the most resistant species to the individual metalsand the combination of metals, Ps. putida the least resistant, and the Salmonellastrains were more resistant than E. coli.Significance and Impact of the Study: Several of the comparison strains withno reported copper resistance were resistant to one or both metals. This maycall into question the methods for determining bacterial metal resistance, whichtypically use nutrient-rich media containing metals to assess the ability of thebacteria to grow in comparison with a wild-type strain. Nevertheless, all theCuR strains evaluated in this study, with the exception of Ent. faecium, werereduced using the Cu and Ag zeolite combination.
- Ikner, L. A., Soto-Beltran, M., & Bright, K. R. (2011). New method using a positively charged microporous filter and ultrafiltration for concentration of viruses from tap water. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 77(10), 3500-6. doi:https://doi.org/10.1128/AEM.02705-10More infoThe methods used to concentrate enteric viruses from water have remained largely unchanged for nearly 30 years, with the most common technique being the use of 1MDS Virozorb filters followed by organic flocculation for secondary concentration. Recently, a few studies have investigated alternatives; however, many of these methods are impractical for use in the field or share some of the limitations of this traditional method. In the present study, the NanoCeram virus sampler, an electropositive pleated microporous filter composed of microglass filaments coated with nanoalumina fibers, was evaluated. Test viruses were first concentrated by passage of 20 liters of seeded water through the filter (average filter retention efficiency was ≥ 99.8%), and then the viruses were recovered using various salt-based or proteinaceous eluting solutions. A 1.0% sodium polyphosphate solution with 0.05 M glycine was determined to be the most effective. The recovered viruses were then further concentrated using Centricon Plus-70 centrifugal ultrafilters to a final volume of 3.3 (±0.3 [standard deviation]) ml; this volume compares quite favorably to that of previously described methods, such as organic flocculation (~15 to 40 ml). The overall virus recovery efficiencies were 66% for poliovirus 1, 83% for echovirus 1, 77% for coxsackievirus B5, 14% for adenovirus 2, and 56% for MS2 coliphage. In addition, this method appears to be compatible with both cell culture and PCR assays. This new approach for the recovery of viruses from water is therefore a viable alternative to currently used methods when small volumes of final concentrate are an advantage.
- Bright, K. R., Boone, S. A., & Gerba, C. P. (2010). Occurrence of bacteria and viruses on elementary classroom surfaces and the potential role of classroom hygiene in the spread of infectious diseases. THE JOURNAL OF SCHOOL NURSING, 26(1), 33-41. doi:https://doi.org/10.1177/1059840509354383More infoThe presence of microorganisms on common classroom contact surfaces (fomites) was determined to identify the areas most likely to become contaminated. Six elementary classrooms were divided into control and intervention groups (cleaned daily with a quaternary ammonium wipe) and tested for heterotrophic bacteria. Three classrooms were also tested for norovirus and influenza A virus. Frequently used fomites were the most contaminated; water fountain toggles, pencil sharpeners, keyboards, and faucet handles were the most bacterially contaminated; desktops, faucet handles, and paper towel dispensers were the most contaminated with viruses. Influenza A virus was detected on up to 50% and norovirus on up to 22% of surfaces throughout the day. Children in the control classrooms were 2.32 times more likely to report absenteeism due to illness than children in the intervention classrooms and were absent longer (on average). Improved classroom hygiene may reduce the incidence of infection and thus student absenteeism.
- Bright, K. R., Marciano-Cabral, F., & Gerba, C. P. (2009). Occurrence of Naegleria fowleri in Arizona drinking water supply wells. JOURNAL - AMERICAN WATER WORKS ASSOCIATION, 101(11), 43-50. doi:https://doi.org/10.1002/j.1551-8833.2009.tb09989.xMore infoNaegleria fowleri is a protozoan found naturally in hot springs and warm surface waters. It can cause usually lethal primary amoebic meningoencephalitis. The goal of this study was to determine the occurrence of N. fowleri in drinking water supply wells in Arizona. Nested polymerase chain reaction was used to detect trophozoites and cysts, but not to assess viability. A total of 185 samples were collected from 113 wells before disinfection. The presence of N. fowleri deoxyribonucleic acid was confirmed in 10.6% of wells. No correlations were found between the presence of N. fowleri and heterotrophic bacteria, coliforms, Escherichia coli, temperature, specific conductance, or turbidity. N. fowleri was detected in 10.0% of initial and 17.2% of purged well samples, suggesting that N. fowleri may be present in the aquifer or detach from the well casing or pump column during pumping.
- Bright, K. R., Sicairos-Ruelas, E. E., Gundy, P. M., & Gerba, C. P. (2009). Assessment of the Antiviral Properties of Zeolites Containing Metal Ions. FOOD AND ENVIRONMENTAL VIROLOGY, 1(1), 37-41. doi:https://doi.org/10.1007/s12560-008-9006-1More infoThe antiviral properties of zeolite (sodium aluminosilicate) powders amended with metal ions were assessed using human coronavirus 229E, feline infectious peritonitis virus (FIPV), and feline calicivirus F-9. Zeolites containing silver and silver/copper caused significant reductions of coronavirus 229E after 1 h in suspension. The silver/copper combination yielded a >5.13-log10 reduction within 24 h. It was also the most effective (>3.18-log10) against FIPV after 4 h. Other formulations were ineffective against FIPV. On plastic coupons with incorporated silver/copper-zeolites, >1.7-log10 and >3.8-log10 reductions were achieved for coronavirus 229E and feline calicivirus within 24 h, respectively. Silver/copper zeolite reduced titers of all viruses tested, suggesting that it may be effective against related pathogens of interest [i.e., SARS coronavirus, other coronaviruses, human norovirus (calicivirus)]. Of note, it was effective against both enveloped and nonenveloped viruses. Metal-zeolites could therefore possibly be used in applications to reduce virus contamination of fomites and thus the spread of viral diseases.
- Blair, B., Sarkar, P., Bright, K. R., Marciano-Cabral, F., & Gerba, C. P. (2008). Naegleria fowleri in well water. EMERGING INFECTIOUS DISEASES, 14(9), 1499-1501. doi:https://doi.org/10.3201/eid1409.071076
- Silvestry-Rodriguez, N., Bright, K. R., Slack, D. C., Uhlmann, D. R., & Gerba, C. P. (2008). Silver as a residual disinfectant to prevent biofilm formation in water distribution systems. APPLIED AND ENVIRONMENTAL MICROBIOLOGY, 74(5), 1639-1641. doi:https://doi.org/10.1128/AEM.02237-07More infoBiofilms can have deleterious effects on drinking water quality and may harbor pathogens. Experiments were conducted using 100 microg/liter silver to prevent biofilm formation in modified Robbins devices with polyvinyl chloride and stainless steel surfaces. No significant difference was observed on either surface between the silver treatment and the control.
- Silvestry-Rodriguez, N., Bright, K. R., Uhlmann, D. R., Slack, D. C., & Gerba, C. P. (2007). Inactivation of Pseudomonas aeruginosa and Aeromonas hydrophila by silver in tap water. JOURNAL OF ENVIRONMENTAL SCIENCE AND HEALTH PART A - TOXIC/HAZARDOUS SUBSTANCES & ENVIRONMENTAL ENGINEERING, 42(11), 1579-1584. doi:https://doi.org/10.1080/10934520701517689More infoThis study was conducted to assess the efficacy of silver as a secondary disinfectant to replace or reduce the level of chlorine utilized in water distribution systems. Pseudomonas aeruginosa and Aeromonas hydrophila are opportunistic pathogens present in drinking water and have been associated with waterborne disease. After 8 hours of exposure to 100 microg/L of silver, there was a >6-log10 reduction in P. aeruginosa in tap water at room temperature at pH7 and a 5.55-log10 reduction in the presence of 3 mg/L humic acid. Similar reductions were observed at pH9. At 4 degrees C, reductions greater than 4-log10 were observed after 24 hours. For A. hydrophila, a >6-log10 reduction occurred at both pH7 and pH9 within nine hours. The World Health Organization has determined that this amount of silver could be used for water disinfection without health risks. Furthermore, silver shows promise as a secondary disinfectant, even in the presence of organic matter in concentrations that would reduce the effectiveness of free chlorine.
- Silvestry-Rodriguez, N., Sicairos-Ruelas, E. E., Gerba, C. P., & Bright, K. R. (2007). Silver as a disinfectant. REVIEWS OF ENVIRONMENTAL CONTAMINATION AND TOXICOLOGY, 191, 23-45. doi:https://doi.org/10.1007/978-0-387-69163-3_2
- Yepiz-Gomez, M. S., Bright, K. R., & Gerba, C. P. (2006). Identity and Numbers of Bacteria Present on Tabletops and in Dishcloths Used to Wipe Down Tabletops in Public Restaurants and Bars. FOOD PROTECTION TRENDS, 26(11), 786-792.More infoDishcloths used in restaurants and bars (23 restaurant, 14 bar cloths) were collected and tabletops (10 restaurants) were swabbed to determine the occurrence of bacteria. Coliforms were isolated from 89.2% of dishcloths and 70% of tabletops. Escherichia coli was isolated from 54.1% of dishcloths and 20% of tabletops. The numbers of heterotrophic plate count bacteria (HPC) and coliforms were significantly higher in bars than restaurants. The levels of HPC found in dishcloths were 25-fold and coliforms were 60- to 120-fold lower than in home dishcloths reported in previous studies. The numbers recovered from restaurant tabletops were also lower than those from household kitchen countertops. The most commonly isolated genera from dishcloths in restaurants and bars differed from those in homes. The numbers found for HPC on restaurant tabletops after cleaning were 45-fold greater than those prior to cleaning. There were also 19-fold greater coliforms and twice as many E. coli. The mandatory use of sanitizers in restaurants and bars may therefore have reduced contamination levels and caused a shift in the microbial populations present in food service establishments. Nevertheless, the implication of dishcloths in contamination of tabletops through cleaning suggests that current monitoring of linen sanitation solutions might be inadequate.
- Rusin, P., Bright, K. R., & Gerba, C. P. (2003). Rapid reduction of Legionella pneumophila on stainless steel with zeolite coatings containing silver and zinc ions. LETTERS IN APPLIED MICROBIOLOGY, 36(2), 69-72. doi:https://doi.org/10.1046/j.1472-765X.2003.01265.xMore infoAIMS: To determine the rate of reduction of Legionella pneumophila by stainless steel surfaces with zeolite ceramic coatings containing 2.5% (w/w) silver (Ag) and 14% zinc (Zn) ions.METHODS AND RESULTS: Stainless steel pans with and without Ag/Zn coatings were inoculated with solutions of Leg. pneumophila ATCC 33155 and incubated at 37 degrees C. Survival was monitored using the spread-plate technique on selective buffered charcoal yeast extract agar. Significant reductions of Leg. pneumophila were effected by the Ag/Zn zeolite coatings within 2 h of exposure.CONCLUSIONS, SIGNIFICANCE AND IMPACT OF THE STUDY: Zeolite ceramic Ag/Zn coatings impart significant anti-Legionella properties to stainless steel surfaces. Coated stainless steel could be used in the manufacture of air ducts, condensation pans and intake and exhaust vents. These products have the potential to reduce numbers of Legionella in air-handling systems.
- Bright, K. R., Gerba, C. P., & Rusin, P. A. (2002). Rapid reduction of Staphylococcus aureus populations on stainless steel surfaces by zeolite ceramic coatings containing silver and zinc ions. THE JOURNAL OF HOSPITAL INFECTION, 52(4), 307-9. doi:https://doi.org/10.1053/jhin.2002.1317More infoThis study demonstrates the anti-Staphylococcus aureus properties of stainless steel surfaces coated with zeolite containing 2.5% silver and 14% zinc ions. Stainless steel panels with and without the heavy-metal-containing coatings were inoculated with S. aureus and incubated at room temperature. Survival of S. aureus was significantly reduced by the silver/zinc coatings within 1 h. Many hospital surfaces could be constructed of stainless steel with silver/zinc zeolite coatings. Such measures may reduce rates of hospital-acquired S. aureus infection.
- Billington, S. J., Jost, B. H., Cuevas, W. A., Bright, K. R., & Songer, J. G. (1997). The Arcanobacterium (Actinomyces) pyogenes hemolysin, pyolysin, is a novel member of the thiol-activated cytolysin family. JOURNAL OF BACTERIOLOGY, 179(19), 6100-6. doi:https://doi.org/10.1128/jb.179.19.6100-6106.1997More infoArcanobacterium (Actinomyces) pyogenes, an animal pathogen, produces a hemolytic exotoxin, pyolysin (PLO). The gene encoding PLO was cloned, and sequence analysis revealed an open reading frame of 1,605 bp encoding a protein of 57.9 kDa. PLO has 30 to 40% identity with the thiol-activated cytolysins (TACYs) of a number of gram-positive bacteria. The activity of PLO was found to be very similar to those of other TACYs, except that it was not thiol activated. The highly conserved TACY undecapeptide is divergent in PLO; in particular, the cysteine residue required for thiol activation has been replaced with alanine. However, mutagenesis of the alanine residue to cysteine did not confer thiol activation on PLO, suggesting a conformational difference in the undecapeptide region of this toxin. Specific antibodies against purified, recombinant PLO completely neutralized the hemolytic activity of A. pyogenes, suggesting that this organism produces a single hemolysin. Furthermore, these antibodies could passively protect mice against lethal challenge with A. pyogenes, suggesting that like other TACYs PLO is an important virulence factor in the pathogenesis of this organism.