Theses and Dissertations
This collection includes both ASU Theses and Dissertations, submitted by graduate students, and the Barrett, Honors College theses submitted by undergraduate students.
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- Creators: Abbaszadegan, Morteza
Description
Bacteria of the Legionella genus are a water-borne pathogen of increasing concern due to being responsible for more annual drinking water related disease outbreaks in the United States than all other microbes combined. Unfortunately, the development of public health policies concerning Legionella has impeded by several key factors, including a paucity of data on their interactions and growth requirements in water distribution networks, a poor understanding of potential transmission sources for legionellosis, and limitations in current methodology for the characterization of these pathogens. To address these issues, a variety of research approaches were taken. By measuring Legionella survival in tap water, association in pipe material biofilms, population dynamics in a model distribution system, and occurrence in drinking water distribution system biofilms, key aspects of Legionella ecology in drinking water systems were revealed. Through a series of experiments qualitatively and quantitatively examining the growth of Legionella via nutrients obtained from several water sources, environmental nutritional requirements and capability for growth in the absence of host organisms were demonstrated. An examination of automobile windshield washer fluid as a possible source of legionellosis transmission revealed Legionella survival in certain windshield washer fluids, growth within washer fluid reservoirs, high levels and frequency of contamination in washer fluid reservoirs, and the presence of viable cells in washer fluid spray, suggesting the potential for exposure to Legionella from this novel source. After performing a systematic and quantitative analysis of methodology optimization for the analysis of Legionella cells via matrix-assisted laser desorption/ionization time-of-flight mass spectrometry, several strains of this microbe isolated from separated and varied environmental water sampling sites were distinctly typed, demonstrating a potential application of this technology for the characterization of Legionella. The results from this study provide novel insight and methodology relevant to the development of programs for the monitoring and treatment of Legionella in drinking water systems.
ContributorsSchwake, David Otto (Author) / Abbaszadegan, Morteza (Thesis advisor) / Alum, Absar (Committee member) / Fox, Peter (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2014
Description
The need for rapid, specific and sensitive assays that provide a detection of bacterial indicators are important for monitoring water quality. Rapid detection using biosensor is a novel approach for microbiological testing applications. Besides, validation of rapid methods is an obstacle in adoption of such new bio-sensing technologies. In this study, the strategy developed is based on using the compound 4-methylumbelliferyl glucuronide (MUG), which is hydrolyzed rapidly by the action of E. coli β-D-glucuronidase (GUD) enzyme to yield a fluorogenic product that can be quantified and directly related to the number of E. coli cells present in water samples. The detection time required for the biosensor response ranged from 30 to 120 minutes, depending on the number of bacteria. The specificity of the MUG based biosensor platform assay for the detection of E. coli was examined by pure cultures of non-target bacterial genera and also non-target substrates. GUD activity was found to be specific for E. coli and no such enzymatic activity was detected in other species. Moreover, the sensitivity of rapid enzymatic assays was investigated and repeatedly determined to be less than 10 E. coli cells per reaction vial concentrated from 100 mL of water samples. The applicability of the method was tested by performing fluorescence assays under pure and mixed bacterial flora in environmental samples. In addition, the procedural QA/QC for routine monitoring of drinking water samples have been validated by comparing the performance of the biosensor platform for the detection of E. coli and culture-based standard techniques such as Membrane Filtration (MF). The results of this study indicated that the fluorescence signals generated in samples using specific substrate molecules can be utilized to develop a bio-sensing platform for the detection of E. coli in drinking water. The procedural QA/QC of the biosensor will provide both industry and regulatory authorities a useful tool for near real-time monitoring of E. coli in drinking water samples. Furthermore, this system can be applied independently or in conjunction with other methods as a part of an array of biochemical assays in order to reliably detect E. coli in water.
ContributorsHesari, Nikou (Author) / Abbaszadegan, Morteza (Thesis advisor) / Alum, Absar (Committee member) / Fox, Peter (Committee member) / Stout, Valerie (Committee member) / Arizona State University (Publisher)
Created2015
Description
Legionella is a gram-negative bacterium with the ability for human infection by inhalation or aspiration of water containing the bacteria. Legionella live in aquatic environments and have been identified in cooling towers, humidifiers and respiratory therapy treatments, among others. Infection with Legionella bacteria leads to Legionnaire’s Disease or Pontiac Fever (Edelstein, 1993). Information regarding the means of aerosolization of Legionella bacteria has not yet been reported, therefore the relevance of experimentation was defined. The objective of this study is to determine the modes by which bacteria may be aerosolized under laboratory conditions. Specifically, to measure the amount of bacteria transported over a specific distance in a given amount of time and determine the most effective mode of bacterial aerosolization. Three methods of bacterial aerosolization were tested, these included an electric paint sprayer, an air paint sprayer and a hand-held spray bottle. E. coli was used as a surrogate for Legionella in experimentation due to its similar bacterial properties. Both bacteria are gram-negative, aerobic bacilli while Legionella is approximately 2 μm in length (Botzenhart, 1998), and E. coli is between 1 and 3 μm in length (Reshes, 2007). The accessibility and non-pathogenicity of E. coli also served as factors for the substitution.
In order to measure the aerosolization efficiency of each spray method, an air sampler was placed opposite to the position of the sprayer, on either side of a sealed box. Each sprayer was filled with E. coli concentrated at 104 CFU/ml in a PBS solution and sprayed for a time span of 1 and 5 seconds. For each of these time intervals an air sample was collected immediately following the spray as well as 5 minutes after the spray. Compared to the other two methods, the air spray method consistently showed the highest number of bacterial cells aerosolized. While all three methods resulted in the aerosolization of bacteria, the results determined the Air Spray method as the most efficient means of bacterial aerosolization. In this study, we provide a practical and efficient method of bacterial aerosolization for microbial dispersion in air. The suggested method can be used in future research for microbial dispersion and transmission studies.
In addition, a humidifier was filled with a spiked solution of E. coli and operated for a period of 1 and 5 seconds at its maximum output. Air samples were collected after 0 and 5 minutes. Immediately after the humidifier operation was stopped a small number of colonies were detected in the air sample and no colonies were detected in the air sample collected after a 5-minute elapsed time. This experiment served as a proof of concept for airborne pathogen’s transmission by a humidifier.
In order to measure the aerosolization efficiency of each spray method, an air sampler was placed opposite to the position of the sprayer, on either side of a sealed box. Each sprayer was filled with E. coli concentrated at 104 CFU/ml in a PBS solution and sprayed for a time span of 1 and 5 seconds. For each of these time intervals an air sample was collected immediately following the spray as well as 5 minutes after the spray. Compared to the other two methods, the air spray method consistently showed the highest number of bacterial cells aerosolized. While all three methods resulted in the aerosolization of bacteria, the results determined the Air Spray method as the most efficient means of bacterial aerosolization. In this study, we provide a practical and efficient method of bacterial aerosolization for microbial dispersion in air. The suggested method can be used in future research for microbial dispersion and transmission studies.
In addition, a humidifier was filled with a spiked solution of E. coli and operated for a period of 1 and 5 seconds at its maximum output. Air samples were collected after 0 and 5 minutes. Immediately after the humidifier operation was stopped a small number of colonies were detected in the air sample and no colonies were detected in the air sample collected after a 5-minute elapsed time. This experiment served as a proof of concept for airborne pathogen’s transmission by a humidifier.
ContributorsJohnson, Chelsea Elizabeth (Author) / Abbaszadegan, Morteza (Thesis director) / Stout, Valerie (Committee member) / School of Life Sciences (Contributor) / Barrett, The Honors College (Contributor)
Created2015-12