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January 2005 - September 2020
Publications
Publications (49)
Paint is a versatile material that can be used to coat surfaces for which routine disinfection practices may be lacking. EPA-registered copper-containing supplemental residual antimicrobial paints could be used to reduce the bioburden on often-neglected surfaces. An interventional study was conducted by painting the walls of a preschool restroom an...
Plant extracts, natural products and plant oils contain natural virucidal actives that can be used to replace active ingredients in commercial sanitizers and disinfectants. This review focuses on the virucidal mechanisms of natural substances that may exhibit potential for indoor air and fomite disinfection. Review of scientific studies indicates:...
Abstract Germicidal ultraviolet (UV) devices have been widely used for pathogen disinfection in water, air, and on food and surfaces. Emerging UV technologies, like the krypton chloride (KrCl*) excimer emitting at 222 nm, are rapidly gaining popularity due to their minimal adverse health effects compared to conventional UV lamps emitting at 254 nm,...
E. coli and Listeria monocytogenes (or L. monocytogenes) are bacteria affecting fresh produce that is harmful for health of humans and animals. If these bacteria are present in surface waterbody (e.g., irrigation canals), they will impair irrigation water quality and threaten produce safety. This paper studied the resuspension of E. coli and Lister...
Fresh produce irrigated with contaminated water poses a substantial risk to human health. This study evaluated the impact of incorporating sediment information on improving the performance of machine learning models to quantify E. coli level in irrigation water. Field samples were collected from irrigation canals in the Southwest U.S., for which me...
Abstract: PhiX174 (or ΦX174) is a spherical single-stranded DNA bacteriophage used as a surrogate to study viral enteric pathogens in the environment. The resuspension of viral pathogen from bed sediment in irrigation canals impairs the quality of overlaying water and can result in the contamination of produce. We conducted a series of laboratory e...
The goal of good toilet hygiene is minimizing the potential for pathogen transmission. Control of odors is also socially important and believed to be a societal measure of cleanliness. Understanding the need for good cleaning and disinfecting is even more important today considering the potential spread of emerging pathogens such as SARS‐CoV‐2 viru...
Irrigation water regulations use Escherichia coli as an indicator of fecal contamination. However, it is well documented that bacterial indicators may not be ideal for predicting viral pathogen presence. Viral pathogens survive relatively long periods in water, are resistant to treatment processes, and cause a large number of illnesses annually. Th...
In December, 2019, a highly infectious and rapidly spreading new pneumonia of unknown cause was reported to the Chinese WHO Country Office. A cluster of these cases had appeared in Wuhan, a city in the Hubei Province of China. These infections were found to be caused by a new coronavirus which was given the name “2019 novel coronavirus” (2019-nCoV)...
The 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 enter...
The 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 extrac...
Contamination 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,...
Questions 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. co...
The 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...
Naegleria fowleri is a thermophilic free-living amoeba found worldwide in soils and warm freshwater. It is the causative agent of primary amebic meningoencephalitis, a nearly always fatal disease afflicting mainly children and young adults. Humans are exposed to the organism via swimming, bathing, or other recreational activity during which water i...
Many plant essential oils, extracts, and individual chemical components have been demonstrated to possess
antiviral efficacy against enveloped and/or non-enveloped viruses. In general, plant antimicrobials exhibit
greater antiviral efficacy against enveloped viruses than non-enveloped viruses (though not in all cases).
There appear to be multiple m...
Many plant essential oils, extracts, and individual chemical components have been demonstrated to possess antiviral efficacy against enveloped and/or non-enveloped viruses. In general, plant antimicrobials exhibit greater antiviral efficacy against enveloped viruses than non-enveloped viruses (though not in all cases). There appear to be multiple m...
Humans are known to be the host to approximately 1500 infectious agents, out of which 66 are protozoa and 287 are helminths. Therefore, from a global perspective helminths and protozoan parasites account for approximately one fourth of the total infectious diseases of humans. A similar trend has been observed in waterborne infectious diseases, amon...
Naegleria 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 c...
Numerous plant compounds have antibacterial/antiviral properties; however, limited research has been conducted with non-enveloped viruses. The efficacies of allspice oil, lemongrass oil, and citral were evaluated against the non-enveloped murine norovirus (MNV), a human norovirus surrogate. The antiviral mechanisms of action were also examined usin...
To investigate the antiviral efficacy of oregano oil and its primary active component, carvacrol, against the nonenveloped murine norovirus (MNV), a human norovirus surrogate.
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 RNa...
The 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, s...
In 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 (CoV22...
Enteric 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,...
The 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 in...
Enteric 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...
The antibacterial efficacy of zeolites containing copper (Cu) or silver (Ag) ions or a combination was assessed against several reported copper-resistant (Cu(R)) bacterial strains.
Comparison strains were obtained from the American Type Culture Collection that had no documented metal resistance. Reductions in bacterial populations were determined a...
The 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...
Based on colony spreading, chitosan from shrimp waste in agar media inhibited the growth of Aspergillus niger by 47.26%; there were not differences (P > 0.05) with respect to commercial chitosan (Fluka, Bio-Chemika) (56.16%). All chitosan films showed similar glass transition temperatures (P > 0.05) with respect to cellophane control; however, chem...
Naegleria 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...
The 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 fo...
The 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 1h in suspension. The silver/copper comb...
Naegleria fowleri is a water-based protozoan found naturally in soil and warm waters. The deaths of two children due to N. fowleri in the Phoenix, Arizona, metropolitan area occurred in 2002, and the drinking water obtained from groundwater was found to be the source of the exposure. A survey was conducted of municipal drinking water wells in centr...
Biofilms can have deleterious effects on drinking water quality and may harbor pathogens. Experiments were conducted using
100 μg/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 co...
This 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...
Silver has been used as an antimicrobial for thousands of years. Over the past several decades, it has been introduced into numerous new venues such as in the treatment of water, in dietary supplements, in medical applications, and to produce antimicrobial coatings and products. Silver is often used as an alternative disinfectant in applications in...
Dishcloths 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 pl...
Pathogenic bacteria are often able to survive for long periods on environmental surfaces, especially under moist or soiled conditions. This often leads to cross-contamination by these pathogens. Many foodborne bacteria such as Salmonella, Listeria monocytogenes, Campylobacter jejuni, and Escherichia coli O157:H7 are commonly found on raw meats and...
RationaleMany fungi colonize indoor environments and produce allergenic proteins that cause adverse health symptoms in sensitive individuals. The effect of sodium hypochlorite (2.4% NaOCl) disinfectant on fungal growth and the presence of allergenic properties was evaluated.Methods
Environmental and laboratory isolates of common indoor mold contami...
Aims: 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 °C. Surviva...
This 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 t...
Arcanobacterium (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. Th...