Doctor of Philosophy, The Ohio State University, 2024, Veterinary Preventive Medicine

The majority of antimicrobials used in dairy production require a veterinarian's prescription; however, farmworkers make daily treatment decisions. Therefore, improving farmworkers' stewardship practices is a fundamental first step in the fight against antimicrobial resistance. This research project aimed to identify gaps in antimicrobial treatment practices between veterinarians and farmworkers, assess the level of agreement in their on-farm therapy options, and understand the barriers and drivers affecting their treatment decisions. Initially, we used a hierarchical survey with clinical case vignettes to understand current on-farm antimicrobial practices between veterinarians and farmworkers. Subsequently, we designed antimicrobial stewardship training to educate farmworkers on accurately identifying cows requiring treatment. Additionally, we quantified antimicrobial use (AMU) through farm treatment records (FTR) and empty drug containers (EDC) during a quasi-experimental study that included intervention and control farms in Ohio and California. Finally, trained farmworkers were individually interviewed using a semi-structured questionnaire, and the interviews were evaluated through thematic analysis. Results indicated that the overall agreement in AMU between veterinarians and farmworkers was generally weak across various disease severity levels. There was significant variation in AMU among the enrolled farms. No significant change in AMU was observed in the intervention farms after the educational training compared to the control farms. FTR underestimated the overall mean treatment incidence by 0.78 times compared to EDC, and the agreement level between them was moderate. Lastly, farmworkers identified six themes with one to three subthemes each. Animal welfare and job success were the primary drivers for improving on-farm AMU. However, they faced significant barriers, including knowledge deficiencies, time-supply constraints, and farm administration issues, whi (open full item for complete abstract)

Committee: Gregory G. Habing (Advisor); Amanda M. Berrian (Committee Member); Thomas E. Wittum (Committee Member); Eric Gordon (Committee Member); Alia M. Dietsch (Committee Member) Subjects: Adult Education; Agriculture; Animal Diseases; Animal Sciences; Behavioral Sciences; Epidemiology; Public Health

Master of Public Health, The Ohio State University, 2022, Public Health

Having risen as a global concern, characterization of antimicrobial resistant (AMR) bacteria within different agricultural landscapes is essential to recognize and mitigate AMR-associated global health risks. Individual animal factors such as lactation stage, parity, and previous antimicrobial use and herd-level factors like size and production type may need to be supplemented with community-level factors such as landscape diversity, density of agricultural animals, soil composition, landscape fragmentation, and connectivity to describe AMR in across agricultural landscapes. Because cephalosporins are used extensively and commensal organisms often harbor resistance in cattle, we investigated herd and community level risk factors of broad-spectrum cephalosporin resistance (BSCR) in cattle across 54 cattle farms in two Ohio counties to explore the role of community-level factors in AMR. From the summer of 2019 through the summer of 2021, interview data, pooled manure samples from cattle, and deer manure samples were collected from farms (n=54) across two counties with different landscape types in Ohio. Proportions of BSCR Enterobacteriaceae were calculated using counts of bacterial colonies grown on non-selective and selective MacConkey agar plates. Herd level predictors included in analysis were outdoor access, other livestock species' presence on the farm, cattle imports to the farm, and herd size. Community level predictors were calculated using a centroid buffer with a 3-kilometer radius around each farm and included cropland diversity, mean dairy kernel density, mean beef kernel density, distance to nearest hospital, distance to nearest wastewater treatment plant, and proportion of broad spectrum cephalosporin resistance in deer manure collected on the property. Beta regression was used to identify significant predictors across both counties combined and stratified by county. Of all models, those including only herd size outcompeted the others in the combined ana (open full item for complete abstract)

Committee: Rebecca Garabed (Advisor); Jiyoung Lee (Committee Member); Stephen Matthews (Committee Member) Subjects: Public Health; Veterinary Services

Doctor of Philosophy, University of Akron, 2018, Polymer Science

The emergence and increasing incidence of drug resistant strains of bacteria is a serious threat to human health. There is an urgent need for the development of new antimicrobial agents to combat bacterial infections that are different from the currently used small molecule drugs. Antimicrobial peptides, a broad family of peptides that are utilized by virtually every organism, are a promising source for new antimicrobial agents to fight pathogenic microorganisms. However, there are many limitations to the widespread use of these peptides, such as the cost of mass production and their rapid degradation in vivo by endogenous proteases. One viable way to overcome these limitations is through using synthetic mimics of these peptides. This work details the design of a new family of antimicrobial, water-soluble polyurethanes that were synthesized to mimic antimicrobial peptides using easily functionalized diols and the subsequent study of their in vitro antimicrobial properties. Studies were performed to determine the effects that a broad range of hydrophobic, uncharged polar, and charged polar pendant groups as well as the effects of molecular weight on the structure/property relationships of these antimicrobial polymers and how they impact antimicrobial efficacy, mammalian cell cytocompatibility, and mechanisms of action.

Committee: Abraham Joy Dr. (Advisor); Nita Sahai Dr. (Committee Chair); Hazel Barton Dr. (Committee Member); Li Jia Dr. (Committee Member); Michael Konopka Dr. (Committee Member) Subjects: Microbiology; Polymers

Doctor of Philosophy, The Ohio State University, 2010, Public Health

It has been previously demonstrated that areas within the hospital that have the highest rates of antimicrobial resistance also have the highest rates of antimicrobial use (AU). The intensive care unit setting is one of the areas within the hospital that has the highest rate of antimicrobial use. Measures of hospital and unit specific AU is assuming increasing importance for understanding the dynamics of antimicrobial resistance at the population level. Data obtained from electronic order entry paired with antibiograms yielded a practical approach to analyze relationships between antibiotic usage and corresponding resistance. We found significant correlations with ciprofloxacin and tobramycin use and imipenem resistance. There was a nonstatistical correlation between imipenem use and imipenem resistance (r = 0.29 for 36 months) but it did indicate a positive correlation. There were also correlations in the pairings of drug and corresponding resistances—inverse correlation for ciprofloxacin use and ciprofloxacin resistance (r = -0.88) and a positive correlation with tobramycin use and tobramycin resistance (r = 0.93). Since changes in AU are paralleled by changes in the prevalence of resistance, application of these methods enable hospitals to monitor antibiotic stewardship program interventions with corresponding changes in the rate of resistance after implementation. Building upon the results from the ecological approach, explored the relationship of antimicrobial use, resistance patterns and risk factors pertinent to specific intensive care units. A case- control study was conducted utilizing patient isolates positive for P. aeruginosa (PA). Cases (n = 78) were patients with positive imipenem-resistant (IRPA) isolates from blood and respiratory cultures. Controls (n = 125) were patients with positive susceptible P. aeruginosa (SPA) isolates. Risk factors analyzed included prior antimicrobial use, comorbid conditions and demographic variables. Time at risk greater (open full item for complete abstract)

Committee: Randall E. Harris MD (Committee Chair); Kurt B. Stevenson MD (Committee Member); Thomas E. Wittum PhD (Committee Member) Subjects: Health Care; Pharmacology; Public Health

Doctor of Philosophy, The Ohio State University, 2013, Food Science and Technology

Edible films and coatings are increasingly being used as carriers of functional additives including antimicrobial agents. Consumer interest in naturally-derived antimicrobials has also increased. Plant extracts such as grape seed and green tea extracts are known to have antiviral as well as antibacterial activities. Even though there are several researches that have investigated the use of edible films and coatings as carriers of antimicrobial agents against foodborne bacterial pathogens, unfortunately data is lacking on the use of these same technologies on foodborne viruses. Therefore, this study seeks to develop edible films and coatings that can control foodborne viruses. The film's antibacterial and mechanical properties were also tested. Chapters 1 and 2 introduce and review previous researches in edible films and coatings. Topics such as the types of biopolymer, film formation methods and mechanisms, foodborne viruses and bacteria, as well as edible film characterization and properties are discussed. Chapter 3 of this study investigated the virucidal activity of green tea extract (GTE) dissolved in deionized water and also incorporated into chitosan film forming solutions (FFS) and into chitosan films. For comparison, the antibacterial activity of the films was also investigated against Listeria innocua and Escherichia coli K12. The viral infectivity after treatments was measured by plaque assays. The 1, 1.5 and 2.5% aqueous GTE solutions significantly (p<0.05) reduced murine norovirus (MNV-1) plaques by 1.69, 2.47, and 3.26 log after 3 h exposure, respectively. Similarly, the FFS containing 2.5 and 5.0% GTE reduced MNV-1 counts by 2.45 and 3.97 log10 PFU/ml, respectively after 3 h exposure. Additionally, the edible films enriched with the GTE (5, 10 and 15%) were also effective against MNV-1. After a 24 h incubation period, the 5 and 10% GTE films significantly (p<0.05) resulted in MNV-1 titer reductions of 1.60 and 4.50 log10 PFU/ml, respectively. The (open full item for complete abstract)

Committee: Melvin Pascall PhD (Advisor); Jianrong Li PhD (Committee Member); Jiyoung Lee PhD (Committee Member); John Litchfield PhD (Committee Member) Subjects: Food Science

Master of Science in Biological Sciences, Youngstown State University, 2025, Department of Biological Sciences and Chemistry

Staphylococcus aureus is recognized as an opportunistic pathogen that causes a wide range of infections. Methicillin-resistant Staphylococcus aureus (MRSA) refers to strains that are resistant to the β-lactam class of antibiotics. Several MRSA strains are multidrug resistant, making treatment of these infections problematic. Further, infections involving biofilm formation are particularly challenging to treat, as biofilms protect bacterial cells from antibiotic penetration. The present investigation examined the effects of laser-irradiated gold nanoparticles (GNPs) on the viability of twelve S. aureus strains. Planktonic cell suspensions containing approximately 20,236 Fe3O4GNPs or 19,784 SGNPs per cell were subjected to 10 minutes of laser exposure and exhibited an average reduction in viability of 89.1% and 78.9%, respectively. Suspensions subjected to laser irradiation alone or nanoparticle exposure alone exhibited little to no reduction in viability. Similarly, S. aureus biofilms were treated with laser-irradiation alone, GNPs alone, or a combination of both treatments. Upon combination treatment, seven of the twelve strains responded positively to treatment, exhibiting an average reduction in biofilm viability of 90%. In contrast, five strains exhibited little to no response to treatment, demonstrating a reduction in viability at or below 25%. Biofilms exposed to one treatment condition alone exhibited little to no reduction in viability. These results suggests that laser-irradiated GNPs may present a promising alternative treatment approach for S. aureus infections, particularly those caused by antibiotic-resistant strains.

Committee: Chester Cooper PhD (Advisor); David Asch PhD (Committee Member); Jonathan Caguiat PhD (Committee Member) Subjects: Biology; Biophysics; Microbiology; Nanoscience

Master of Science (MS), Bowling Green State University, 2024, Biological Sciences

Muco-obstructive illness is caused by any number of defects in the respiratory tract that result in viscous or static mucus. This creates an environment conducive for pathogen colonization with subsequent synergistic interactions that drive selection of a smaller set of apex pathogens, resistant to immune and antibiotic intervention. Successful control and potential resolution of such infections will require the development of new therapeutic strategies. One potential approach involves identification of bacterial viruses that target the dominant bacterial strains that manifest in patients with compromised respiratory functions. This study considers a set of bacteriophage specific for, and toxic to Burkholderia species that often dominate in such patient populations. I isolated a set of bacteriophage from environmental samples (including soil, human sewage, and agricultural waste for consideration. Some environmental isolates were capable of infecting pathogenic Burkholderia and a suite of lab adapted and pathogenic Burkholderia strains. As a result of this bacteriophage hunt, 15 potential bacteriophage isolates have been maintained, four of which have been sequenced and analyzed further. To do so, DNA was extracted from the purified and amplified isolates and sequenced. Thus, it was postulated that the novel bacteriophages “Clear “and “Cloudy” may be related to the P2-family of bacteriophage: whereas novel bacteriophage “P1P” contains elements similar to mu-like phage. Further research is necessary to detail the genome structure, genetic relationships, and gene function; however, these novel isolates reiterate the notion that pathogen-infecting bacteriophage are potentially isolated from the environment using non-pathogenic or pathogenic strains.

Committee: Raymond Larsen Ph.D. (Committee Chair); Hans Wildschutte Ph.D. (Committee Member); Simon Morgan-Russell Ph.D. (Committee Member) Subjects: Microbiology

Doctor of Philosophy, The Ohio State University, 2024, Animal Sciences

Salmonella, a foodborne zoonotic pathogen, is the leading cause of death associated with foodborne illness in the USA. Salmonellosis is primarily transmitted through the consumption of contaminated poultry meat and eggs. The irrational use of antibiotics to control Salmonella infection in poultry has led to the emergence of multidrug-resistant (MDR) strains and its horizontal transmission to humans. Additionally, vaccines used to prevent Salmonella infection do not provide cross-protection to heterologous serotypes of Salmonella. Therefore, there is an urgency of the development of novel antimicrobials to control Salmonella infection. Studies have shown that small specialty crop farms (SSCFs), which practices mixed farming, are reservoirs of MDR Salmonella. Regular monitoring is needed to reduce the risk of MDR Salmonella transmission from SSCFs to humans. To this end, we isolated Salmonella from 29 of 1174 environmental samples such as dairy and poultry manure, soil, and water of SSCFs. From 29 positive samples, 80 isolates were subjected to whole genome sequencing (WGS) to determine the serotypes, antimicrobial resistance genes, virulence genes, plasmids to understand the potential risk of its transmission. Our results detected the presence of ACSSuT cassette in six Salmonella isolates, which confers resistance to ampicillin, chloramphenicol, sulfonamide, streptomycin, and tetracycline, demonstrating the urgency to develop the novel antimicrobials to combat MDR Salmonella. Therefore, we assessed the activity of novel antibiotics alternatives such as probiotics and anti-microbial peptides (AMPs) against Salmonella. The anti-Salmonella activity of probiotics and AMPs characterized in our study could lay foundation as novel antimicrobials against Salmonella. In silico serotyping of Salmonella isolated from SSCFs identified 15 serotypes of Salmonella. Eight out of 15 serotypes reported in our study are among the top 20 serotypes frequently reported in human salmone (open full item for complete abstract)

Committee: Gireesh Rajashekara (Advisor) Subjects: Biology

Honors Theses, Ohio Dominican University, 2024, Honors Theses

The use of touchscreens in today's world has increased drastically, especially in healthcare. The spread of pathogenic microbes from touchscreens to people has been a cause for concern in recent years. The ability to create an antimicrobial touchscreen would help stop the spread of pathogenic bacteria not only in healthcare but anywhere touchscreens are utilized. To create a material that could be incorporated into touchscreens to make them antimicrobial, they would need to kill microbes, be optically transparent, and be able to conduct electricity. Our research tested the antimicrobial properties of graphene-copper chalcogenide composite materials, specifically graphene-copper oxide and graphene-copper sulfide. Graphene-copper sulfide was synthesized and both materials were analyzed using X-ray photoelectron spectroscopy. These materials were tested against B. subtilis and E. coli using standard agar disk diffusion. Both composite materials displayed antimicrobial activity against B. subtilis. Our data show a promising first step in creating an antimicrobial touchscreen.

Committee: Annie Witzky Ph.D. (Advisor); John Marazita Ph.D. (Committee Member); Daniel Little Ph.D. (Advisor) Subjects: Chemistry; Microbiology

Master of Science, The Ohio State University, 2024, Animal Sciences

Listeria monocytogenes is an invasive, zoonotic, foodborne pathogen that causes human listeriosis. L. monocytogenes is a resilient pathogen capable of surviving and even proliferating under various environmental conditions. Its capacity to persist in soil, manure, water, and various farm environments necessitates an investigation to safeguard consumers and maintain the reputation of small specialty crop farms. Small specialty crop farms (SSCFs) are an important and growing sector for crop production in the USA. Currently, there is little information on the prevalence and genetic landscape of the L. monocytogenes from SSCFs. Bridging this knowledge gap would help understand potential public health risks associated with the L. monocytogenes coming from these farms. The goal of our study is to understand the prevalence and genomic diversity among the isolates in the SSCF niche by characterizing pangenome, serogroups, antimicrobial resistance genes, and virulence genes. We collected, tested, and processed dairy and poultry manure, soil, water, and produce samples (n = 1842) for L. monocytogenes from 15 SSCF between 2016 to 2020. Isolates were analyzed through Whole Genome Sequencing (WGS). The overall prevalence of L. monocytogenes on SSCF was 7.17% (132/1842 samples). Based on positive samples, the prevalence of L. monocytogenes was 23.2% (n=53/228) in dairy manure, 11.0% (n=14/127) in water, 6.2% (n=31/500) in produce, 3.6% (n=28/777) in soil, 2.9% (n=6/210) in poultry manure. From these 132 positive samples, 347 isolates were obtained and were subjected to whole genome sequencing (WGS). Pangenome analysis detected the presence of 2,036 core genes. In silico serotyping of L. monocytogenes detected the presence of four serotypes 1/2a, 1/2b, 1/2c, and 4b, implicated in human infections. Analysis of antimicrobial resistance (AMR) genes identified the presence of 10 genes: abc-f, fos(X), mecA, vanZ, mprF, mprB, vga(G), ampC, group_1242, and tetR. In addition, an arsenic- (open full item for complete abstract)

Committee: Gireesh Rajashekara (Advisor); Joy Scaria (Committee Chair); Greg Habing (Committee Chair) Subjects: Animal Sciences; Microbiology; Public Health

Master of Science, University of Akron, 2024, Polymer Science

Dental caries are caused by oral microbiota producing acid via sugar metabolism. Streptococcus mutans (S. mutans) is the predominant aerobic cariogenic pathogen within dental plaque, whereas Fusobacterium nucleatum (F. nucleatum) represents anaerobic bacteria associated with periodontal disease and some inflammatory diseases, including irritable bowel syndrome and rheumatoid arthritis. Bacteria may develop antimicrobial resistance to traditional antibiotics and Ag NPs but not Silver-doped hydroxyapatite nanoparticles (AgHAP NPs), making the latter an attractive biocompatible material for dental applications. The Sahai group's previous studies showed (a) Ag content of AgHAP NPs depends on synthesis pH and (b) AgHAP NPs' antibacterial effects were shown by inhibition zone experiments but, in an apparent contradiction, relatively high MIC values were obtained for anaerobic bacteria F. nucleatum. The goals of the present study were to determine the antibacterial effects of AgHAP NPs with different synthesis pHs (pH7.5, 8, 8.5) on aerobic S. mutans and anaerobic F. nucleatum and to determine why MIC values were unexpectedly high for anaerobic strain F. nucleatum. Antimicrobial tests (MIC, inhibition zone, SEM visualization) showed antibacterial activity of AgHAP NPs which was related to Ag content and Ag+ release from NPs. Ionic conductivity measurements for Ag+ solutions with or without L-Cysteine under anaerobic and aerobic conditions were conducted, showing a dramatic drop in conductivity value only with the presence of L-Cysteine. Accepting the hypothesis that Ag+-thiol complexation reduces the availability of the toxic agent (Ag+) in the growth medium of F. nucleatum, which requires L-Cysteine to maintain anaerobic conditions. Thus, MIC values obtained were spuriously high, while inhibition zone results showed the true efficacy of AgHAP NPs against F. nucleatum.

Committee: Nita Sahai (Advisor); Ali Dhinojwala (Committee Member) Subjects: Biochemistry; Chemistry; Dentistry; Materials Science

Doctor of Philosophy, University of Akron, 2024, Polymer Engineering

Two-dimensional (2D) nanomaterials, such as graphene and transition metal dichalcogenides have been at the forefront of materials science due to their excellent and tunable mechanical, electrical, thermal, and optical properties. But they also have limitations including processability, scalability, and high cost, which constrain their applications in many fields. One strategy to overcome such limitations is to integrate 2D nanomaterials with other functional components including polymers and metallic nanostructures. The synergistic interactions between those components can lead to unprecedented properties. In this research, we focus on how to design functional nanocomposites based on the integration of 2D nanomaterials and other components, with targeted applications in solid lubrication and filtration/molecular separation. In the first study, we demonstrated that by integrating graphene oxide and polydopamine into sprayable nanocoatings, they can substantially enhance the filtration performance of filters based on polymer fiber network. In the second study, we showed that by in situ synthesis of graphene/titanium oxide hybrid nanosheets and transforming them into nanoscrolls, they can act as high-performance solid lubricants due to the high stability and significantly reduced contact area. In the third study, we demonstrated that the integration of 2D Fe2O3 nanosheets and graphene by a scalable microwave-assisted method, high-performance solid lubricants can be created, which substantially reduced the friction between steel-to-steel or steel-to-silicon. This research provides insight into the rational design and synthesis of functional 2D nanocomposites and can be further explored in areas including energy conversion/storage, catalysis, and advanced manufacturing.

Committee: Weinan Xu (Advisor); Christopher DellaCorte (Committee Member); Yu Zhu (Committee Member); Fardin Khabaz (Committee Chair); Ali Dhinojwala (Committee Member) Subjects: Aerospace Materials; Automotive Materials; Engineering; Materials Science; Nanotechnology; Organic Chemistry; Plastics

Master of Science (MS), Ohio University, 2023, Biomedical Engineering (Engineering and Technology)

Abstract GUGGENBILLER, GRANT W., M.S., December 2023, Biomedical Engineering Electrospun Composite With Tunable Morphology for Burn Wound and Soft Tissue Wound Recovery Applications Director of Thesis: Dr. Andrew C. Weems Electrospinning offers a unique opportunity to produce micro- or nanoscale features using a wide array of polymers to produce 3D porous scaffolds. Here, a series of bioderived, pro-drug photopolymers, derived from salicylic acids, are photocrosslinked in the presence of polystyrene and silver sulfate to achieve a series of composite fibrous mats. The use of the three components (photopolymer, polystyrene, silver sulfate) are shown to provide an avenue towards tuning the fiber morphology. These materials display shape memory, allowing for minimally invasive medical device opportunities, as well as cytocompatibility and antimicrobial behaviors. Ultimately, these composite fibrous mats display excellent promise for both implantable tissue scaffolds as well as for medical devices including face masks or wound coverings.

Committee: Andrew Weems PhD (Advisor); Martin Kordesch PhD (Committee Member); Erin Murphy PhD (Committee Member); Douglas Goetz PhD (Committee Member) Subjects: Biomedical Engineering; Engineering; Plastics

Master of Science, The Ohio State University, 2023, Environment and Natural Resources

Antibiotic-resistant bacteria (ARB) pose a growing threat to public health by rendering antibiotic treatments ineffective and causing prolonged hospital stays, increased healthcare expenditures, and greater mortality. Of particular concern are those resistant to carbapenems, powerful antibiotics used for life-threatening infections. Carbapenem-resistant Enterobacteriaceae (CRE) and carbapenem resistance genes are established in surface waters through hospital and wastewater effluent. However, little is known about their presence in aquatic wildlife. Transmission of CRE from aquatic to terrestrial systems could introduce CRE into animal operations and subsequently the human food supply. Therefore, it is crucial to understand pathways of dissemination within and between aquatic and adjacent riparian organisms. This study investigated the effects of (1) fish-based ecological network structure and (2) trophic position and diet composition on carbapenem resistance in linked river-riparian reaches surrounding six wastewater treatments plants discharging into medium-to-large rivers in Cincinnati, Columbus, and Cleveland, Ohio. Carbapenem resistance was present at all six sites, with CRE genes recovered from multiple environmental samples over two sampling years. Carbapenem resistance was not observed in any samples of aerial insectivorous birds feeding in sample reaches (Tree Swallow Tachycineta bicolor). 10.5% of fish isolates exhibited carbapenem resistance, and 4.67% of fish isolates yielded CRE genes. Model selection of negative binomial models revealed that nutrient concentrations and turbidity were strongly supported predictors of carbapenem occurrence in fish communities. Ecological network properties including linkage density (i.e., number of interactions per species), compartmentalization (i.e., degree of connectedness of subgroups within a network), and variability in the magnitude of interactions were also important predictors. Carbapenem resistance generally (open full item for complete abstract)

Committee: Stephen Matthews (Advisor); Thomas Wittum (Committee Member); S. Mažeika Patricio Sulliván (Advisor) Subjects: Ecology; Freshwater Ecology

Doctor of Philosophy, University of Akron, 2023, Polymer Science

Polyurethanes are a versatile class of polymers that have been used in various applications ranging from coatings to medical devices. The chemical structure of polyurethane can be modified to obtain desired properties. Herein, we demonstrated the ability to modulate functional groups of polyurethanes to tailor their properties in two platforms, segmented polyurethane for degradable biomaterials and random polyurethane copolymers for enhancing the antimicrobial action of antibiotics. Medical devices made from segmented polyurethanes are generally bio-inert and have very low surface wettability. Although there are multiple approaches being employed for surface functionalization, each approach has significant deficiencies such as low surface functionalization or the need for complicated processes. Through this work, I was seeking to improve our fundamental understanding of how bulk functionalization will affect the presence of functional groups at the surface. The work sought to correlate the positional variation of the cationic amine group in either the soft or hard segment to the mechanical and surface properties of modified segmented polyurethanes. Furthermore, the degradation profile of cationic segmented polyurethanes in oxidative and hydrolytic environments was examined and correlations between the degradation profile and the the polyurethane compositions were developed. Antibiotic-resistant bacterial infections are one of the most pressing problems costing billions of dollars to the healthcare system. In particular, gram-negative bacterial infections are challenging to cure since gram-negative bacteria have an outer membrane acting as a selective membrane barrier. This work demonstrates how cationic polyurethanes can act as an outer membrane destabilizer. This work shows that the combination of a cationic polyurethane along with an antibiotic that is not able to traverse an intact outer membrane, is an effective treatment for multi-drug resistant bac (open full item for complete abstract)

Committee: Abraham Joy (Advisor); James Eagan (Committee Chair); Hazel Barton (Committee Member); Weinan Xu (Committee Member); Kevin Cavicchi (Committee Member) Subjects: Chemistry; Microbiology; Plastics

Doctor of Philosophy, The Ohio State University, 2023, Comparative Biomedical Sciences

Urinary tract infections (UTIs), including cystitis and pyelonephritis, are one of the most common infections across species. Approximately 80% of these infections are caused by uropathogenic Escherichia coli (UPEC). The host's innate immune response is paramount in the defense against UPEC and is initiated by urinary tract epithelial cells with subsequent recruitment of leukocytes. Despite a robust immune response, UPEC can persist in the urinary tract, can cause recurrent infections, and can be resistant to antibiotic therapy. There is a growing and imminent risk for antibiotic resistant UTIs, thus necessitating investigations into alternative therapeutic options. One possibility is utilizing mechanisms to enhance existing host innate immune defenses; however, our understanding of innate immunity against UPEC, especially in the kidney, is limited. In this work, we aimed to characterize the host immune response to UPEC in cell culture and in various important mouse models of UTI to identify potential targets for augmenting host defense against UPEC. The first portion of this thesis investigates the in vitro pathogenesis of UPEC in one of the host's most important UTI renal defenders, the kidney collecting duct intercalated cell. Previous work from our lab and others have shown that intercalated cells are required for protection against UPEC due to direct binding to these cells, their role in immune cell recruitment, and secretion of bactericidal antimicrobial peptides. We found that upon UPEC infection, intercalated cells activate multiple innate immune pathways including those associated with pattern recognition receptor (PRR) signaling. We identified that nucleotide oligomerization domain (NOD) 2 and Toll-like receptor (TLR) 4 are two intercalated cell PRRs that, upon initial activation, can protect against subsequent UPEC infection. Additionally, NOD2 activation induces upregulation of multiple innate immune pathway genes along with genes associated with vari (open full item for complete abstract)

Committee: John David Spencer (Advisor); Kara Corps (Committee Member); Rachel Cianciolo (Committee Member); Brian Becknell (Committee Member); Sheryl Justice (Advisor) Subjects: Biology; Immunology; Microbiology; Molecular Biology; Pathology

Doctor of Philosophy, The Ohio State University, 2023, Biomedical Sciences

Antibiotic resistance is an urgent public health problem and is associated each year with over a million deaths worldwide. Strategies to limit antibiotic exposures as well as improved practices for infection prevention and containment have been successful in reducing the emergence and spread of antibiotic resistance. Despite these efforts, novel therapeutic strategies are needed. In this dissertation, we investigate the induction of sugar-phosphate toxicities as a novel therapeutic modality to selectively target microbial pathogens. We use Salmonella enterica serovar Typhimurium, as our model pathogen, due to its clinical relevance, tractable genetics, and well-developed mouse models for studying infection. It is also one of the most characterized microbes and many aspects of its physiology and pathogenesis are relevant to other pathogens of the Enterobacteriaceae family for which antibiotic resistance is of paramount concern [i.e., the Carbapenem-resistant Enterobacteriaceae (CRE) and extended spectrum beta-lactamase (ESBL)-producing pathogens]. Here, we have assembled and characterized a collection of Salmonella mutants predicted to suffer sugar-phosphate toxicity due to the absence of targeted enzymes within a variety of sugar-utilization pathways. Elimination of these enzymes coupled with the provision of the appropriate sugar leads to the accumulation of toxic sugar-phosphate intermediates resulting in growth inhibition. These mutations serve as a proxy for small molecule inhibitors of those enzymes that would be used in real-world therapeutic applications. Of the seven mutants tested in vitro, five (galE, galT, rhaD, mtlD, and araD) mutants showed growth inhibition in addition to a fraB mutant reported in earlier work. All but the galT mutant were also attenuated in a mouse model of Salmonella-mediated gastroenteritis. While homologs of galE are widespread among bacteria and in humans, the araD, mtlD, rhaD, and fraB genes are rare in most phyla of bacteria a (open full item for complete abstract)

Committee: Brian Ahmer Ph.D. (Advisor); Venkat Gopalan Ph.D. (Committee Member); Vanessa Hale DVM, MAT, Ph.D. (Committee Member); John Gunn Ph.D (Committee Member) Subjects: Biomedical Research; Microbiology; Molecular Biology

Doctor of Philosophy, The Ohio State University, 2022, Biomedical Sciences

Infections and disease caused by the obligate human pathogen Bordetella pertussis (Bp) are resurging worldwide, despite widespread vaccinations. The current acellular pertussis vaccines remain ineffective against nasopharyngeal colonization, carriage, and transmission. To develop more effective vaccines, it is important to understand how Bp resists killing actions of host immunity. In the current work, we tested the hypothesis that Bordetella polysaccharide (Bps), a member of the poly-􀈕-1,6-N-acetyl-D-glucosamine (PNAG) family, promotes respiratory tract colonization of Bp by resisting killing from two major innate immune factors: (1) antimicrobial peptides (AMPs) and (2) neutrophils. First, we show that Bps enhanced Bp survival in the presence of AMPs by functioning both as a surface shield and a decoy. While surface-bound Bps inhibited AMP binding to the bacterial surface, soluble Bps neutralized AMP activity by direct binding interactions. Simultaneous infection of mice with Bps-proficient and Bps-deficient strains resulted in greater survival of the Bps-deficient strain in the mouse respiratory tract. Furthermore, production of Bps in a nonpathogenic E. coli strain increased AMP resistance in vitro, and increased bacterial survival and augmented pathology in the mouse respiratory tract. Second, we show that Bps enhanced survival in the presence of hydrogen peroxide and hypochlorous acid in vitro. Consistent with these data, Bps enhanced resistance to killing by human neutrophils and suppressed oxidative burst and neutrophil extracellular trap (NET) formation. Together, the results obtained from studies involving AMPs and neutrophils serve as a foundation for studying other PNAG polysaccharides, as well as for the development of an effective Bp vaccine that includes Bps. Traditionally, pertussis is described as an acute disease with coughing fits and other severe symptoms. However, in recent years, many individuals who contract pertuss (open full item for complete abstract)

Committee: Rajendar Deora Ph.D. (Advisor); Paul Stoodley Ph.D. (Committee Chair); Daniel Wozniak Ph.D. (Committee Member); Santiago Partida-Sanchez Ph.D. (Committee Member); John Gunn Ph.D. (Committee Member) Subjects: Biomedical Research; Immunology; Microbiology

Doctor of Philosophy, The Ohio State University, 2022, Food Science and Technology

Cross-contamination is one of the main pathways by which pathogens enter, survive, and grow in the foods we consume. To address this issue, a tried and proven method is the use of antimicrobial packaging materials that could inactivate microorganisms. Quaternary ammonium compounds (QACs) were documented to be effective against Gram-positive and negative bacteria, enveloped and non-enveloped viruses, and can be used as coating materials on stainless-steel surfaces. This dissertation reports on studies done on dry and wet abrasion testing of a silane QAC antimicrobial coating on a stainless-steel substrate using the contact-based approach. The first part of this dissertation (Chapter 3) studied the resilience of the coating material (first and second applications) to repeated dry abrasions while still maintaining its antimicrobial efficacy to Listeria innocua and Escherichia Coli K12 (L. innocua and E. coli K12), as well as the physio-chemical changes to the coatings during dry abrasions. The antimicrobial performances of the coating were tested by inoculating bacteria on the coated surfaces before and after dry rubbings. Physio-chemical changes to the coating were determined using SEM/EDS analysis (Scanning electron microscopy and energy dispersive X-ray spectroscopy). The results showed that the coating inactivated L. innocua and E. coli K12 after 60 and 120 rub cycles, respectively. A second application of the coating, after the first coating was removed by dry abrasion, gave the stainless-steel a similar inactivation ability against L. innocua when compared with the first coating. The SEM/EDS analysis showed a decline in the carbon, oxygen, silicon, and chlorine compositions in the coated surface after 120 rub cycles. This provided information about how the dry abrasion degraded the coating. The second part of this dissertation (Chapter 4) evaluated the resilience of the coating material to repeated wet abrasions with an industrial detergent and how many washi (open full item for complete abstract)

Committee: Melvin Pascall (Advisor); Xiaoguang Wang (Committee Member); Hua Wang (Committee Member); Lynn Knipe (Committee Member) Subjects: Food Science

Master of Science, The Ohio State University, 2022, Comparative and Veterinary Medicine

Pseudomonas syringae pv. syringae (Pss) is an emerging seed-borne pathogen that causes Pseudomonas leaf spot (PLS) disease in bell peppers. It causes severe necrotic lesions on pepper leaves that can spread to 50-80% of the field under favorable environmental conditions. PLS can cause significant economic losses to pepper production if the disease is left uncontrolled. However, not much is known about the genes that Pss carries to be able to cause disease in peppers. It is important to understand the virulence genes that Pss carries so that appropriate measures can be developed to control Pss in peppers. Therefore, part of my research aimed to use comparative genomic analysis to understand the genes in Pss that are important for virulence in pepper seedlings. The Pss strains (n=16) evaluated showed varying levels of virulence (disease severity and Pss population) at 3-, 7-, and 14-days post-infection (dpi) on the susceptible 'California Wonder' pepper variety in a controlled growth chamber environment. The Pss strains also displayed varying growth, biofilm development, and motility in vitro in M9 minimal broth at 28˚C, however, the variation in in vitro performance did not explain the variation in the virulence of the Pss strains in pepper seedlings. Whole genome sequencing was performed on these Pss strains. The genes were functionally characterized, and core genomes were separated from the variable genomes between the Pss strains. A total of 812 genes were variable among the Pss strains including known virulence genes. Additionally, a multivariate correlation analysis identified 285 genes that were significantly correlated to the virulence of Pss in pepper seedlings (r2 of  0.5 to 0.675; P<0.01). The genes that were significantly correlated with the virulence of Pss strains included known virulence genes associated with motility (n=2), biofilm (n=5), and Type III and VI secretion systems (T3SS and T6SS) (n=9). Further, the two strains (SM156-18 and SM226-1) that (open full item for complete abstract)

Committee: Gireesh Rajashekara (Advisor); Sally Miller (Committee Member); James Fuchs (Committee Member) Subjects: Biology; Microbiology; Plant Pathology