abstract: The increasing pervasiveness of infections caused by multidrug-resistant bacteria (MDR) is a major global health issue that has been further exacerbated by the dearth of antibiotics developed over the past 40 years. Drug-resistant bacteria have led to significant morbidity and mortality, and ever-increasing antibiotic resistance threatens to reverse many of the medical advances enabled by antibiotics over the last 40 years. The traditional strategy for combating these superbugs involves the development of new antibiotics. Yet, only two new classes of antibiotics have been introduced to the clinic over the past two decades, and both failed to combat broad spectrum gram-negative bacteria. This situation demands alternative strategies to combat drug-resistant superbugs. Herein, these dissertation reports the development of potent antibacterials based on biomolecule-encapsulated two-dimensional inorganic materials, which combat multidrug-resistant bacteria using alternative mechanisms of strong physical interactions with bacterial cell membrane. These systems successfully eliminate all members of the ‘Superbugs’ set of pathogenic bacteria, which are known for developing antibiotic resistance, providing an alternative to the limited ‘one bug-one drug’ approach that is conventionally used. Furthermore, these systems demonstrate a multimodal antibacterial killing mechanism that induces outer membrane destabilization, unregulated ion movement across the membranes, induction of oxidative stress, and finally apoptotic-like cell death. In addition, a peptide-encapsulation of the two-dimensional material successfully eliminated biofilms and persisters at micromolar concentrations. Overall, these novel systems have great potential as next-generation antimicrobial agents for eradication of broad spectrum multidrug-resistant bacteria. / Dissertation/Thesis / Doctoral Dissertation Chemistry 2019

Indiana University-Purdue University Indianapolis (IUPUI) / For regenerative endodontic procedures (REPs) to be successful an elimination of bacteria from the root canal system must be accomplished. Many different medicaments with antibacterial properties have been used to obtain complete disinfection. Double antibiotic paste (DAP) containing a mixture of ciprofloxacin and metronidazole has been shown to be a promising intracanal medicament. The addition of a radiopaque filler such as zirconium oxide to DAP may affect the antibacterial properties of DAP as well as allow precise placement and radiographic visualization of its position in the canal system. The aim of the proposed study was to evaluate the direct antibacterial properties of zirconium oxide radiopacifier combined with DAP (RoDAP) against a multispecies biofilm from a bacterial isolate from an infected immature tooth with a necrotic pulp and a known single species biofilm. 4x4 mm radicular dentin specimens (n = 112) obtained from human extracted teeth were used prepared and sterilized prior to use. A multispecies clinical bacterial isolate from an immature tooth with a necrotic pulp and a single species Enterococcus faecalis isolate were obtained. These bacterial isolates were used to inoculate dentin slabs and grown for 3 weeks. The dentin slabs were treated for 1 week with 1.0-mg/mL and 10- mg/mL RoDAP, 1.0-mg/mL DAP, and two placebo pastes consisting of methyl cellulose (MC) and methyl cellulose combined with zirconium oxide (RoMC), respectively, as well as two no-treatment controls. Following treatment, the grown biofilm was detached and spiral plated. The plated biofilm cells were cultured for 24 hours and each group examined using a colony counter to determine bacterial numbers (CFUs/mL). Data analysis, using a 5.0-percent significance level was conducted using one-way ANOVA followed by pair-wise group comparisons. Both 1.0-mg/mL and 10 mg/mL RoDAP demonstrated significant antibacterial effects against bacterial isolates from an immature tooth with a necrotic pulp as well as an E. faecalis isolate. The precise application of RoDAP confirmed radiographically with its direct antibacterial properties may be beneficial for intracanal disinfection during REPs.

No description available.

Introduction: The primary reason for endodontic treatment failure is microbial infection inside the root canal system by different microbes including Enterococcus faecalis. Endodontic sealers with Chitosan (CS), a compound with antimicrobial effects, can decrease the growth of microorganisms and potentially prevent failure. Purpose: The aim of this study was to assess the antimicrobial activity ex-vivo and flowability of calcium silicate root canal sealers with added CS fillers. Materials and methods: EndoSequence (BC) sealer was mixed with CS fillers in two different concentrations (5% and 10%wt). Flowability was analyzed according to ISO-6876. The antibacterial assessment was conducted using an ex-vivo model. Extracted single-rooted teeth were infected with E. faecalis for 7 days. Follow the root canal treatment, the sealers (BC, BC+CS-5%, BC+CS-10%, N=6) were used for obturation and re-incubated in the bioreactor for 24 hours. Untreated teeth were used as positive control. Cell viability (CFU/mL) and fluorescence microscopy were used to determine the number of bacteria at the bonded interface. ANOVA was used for statistical analysis. Results: Addition of CS fillers into BC resulted in a significant decrease in flowability (BC:22mm, BC+CS-5%:19mm, BC+CS-10%:16mm). All evaluated sealers showed antibacterial activity. The addition of CS significantly reduced the viable cells (log(CFU/mL)) (CS-5%:5.3, CS-10%:4.6) compared with the BC (5.9) and positive control (7.2). Fluorescence analysis showed that CS-Sealers group had an increased number of dead cells (CS-10%:77.3%, CS-5%:64.4%) compared with the BC-Sealer (37.9%) and positive control (23.3%). Conclusion: Endodontic sealers with added CS enhanced antimicrobial effects of the sealer. However, adding more than 5% of CS affects the flow properties of the sealer. / Oral Biology

No description available.

The safety of healthcare workers (HCW) has become a serious concern; therefore, a need for protection against bacterial penetration and transmission is realized. The purpose of this research is to examine whether antibacterial finishes can effectively reduce the presence of bacteria that have the potential for penetration and transmission on healthcare workers uniforms (HCWU). The specific objective of this research is to compare the antibacterial properties (i.e., bacterial reduction), two descriptive properties (i.e., fabric weight, fabric thickness), and one durability property (i.e., breaking strength loss due to abrasion) of a 65/35% polyester/cotton blend fabric treated with two commercially available antibacterial agents (i.e., 3-trimethoxysilylpropyldimethyloctadecyl ammonium chloride) or AEGIS Microbeshield, (AMS) and polyhexamethylene biguanide (PHMB) or Reputexâ · before laundering and after 5, 10, and 25 laundering cycles. The independent variables were the treatments (i.e., AMS, PHMB, no treatment) and the laundering cycles (i.e., 0, 5, 10, 25). The dependent variables were the four fabric properties: (a) antibacterial properties against Staphylococcus aureus (S. aureus) and Klebsiella pneumoniae (K. pneumoniae) bacteria, (b) fabric weight, (c) fabric thickness, and (d) breaking strength loss due to abrasion. Multiple Analysis of Variance (MANOVA) and Two-way Analysis of Variance (ANOVA) were used to examine the effects of the independent variables and their interaction on each dependent variable. The results showed PHMB treated specimens had a significantly higher log reduction against both S. aureus and K. pneumoniae before laundering and after 5, 10 and 25 laundering cycles than AMS treated specimens and the no treatment specimens. Initially, AMS had some reduction against S. aureus and K. pneumoniae before laundering; however after laundering, the reductions against both bacteria were diminished greatly. As expected, the no treatment specimen had no reduction against S. aureus or K. pneumoniae before and after laundering. The addition of PHMB and AMS increased the fabric weight of 65/35% polyester/cotton fabric and kept the fabric thickness throughout 25 laundering cycles. The untreated specimens became thicker after 25 laundering cycles. In addition, the breaking strength loss due to abrasion indicated that treatments had no effect on fabric strength. In conclusion, adding antibacterial agents do have some influence on bacterial reduction for both Gram-positive and Gram-negative bacteria as well as descriptive properties (i.e., fabric weight, fabric thickness). However, there was no influence on durability property (i.e., breaking strength loss due to abrasion). More studies are needed to test both agents on other types of fabrics such 100% cotton and nonwoven to incorporate more treated HCWU in the marketplace. / Ph. D.

The effect of butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), tertiary-butyl hydroquinone (TBHQ) and 8- hydroxyquinoline (8-0HQ) upon cell growth and spore germination of Clostridium botulinum type 62A was studied using a complex liquid medium. The inhibition of spore germination was further investigated using a defined liquid medium containing L-alanine, L-lactic acid and NaHC0₃. Cell growth was monitored by optical density (600 nm) increase and germination was monitored either by optical density (600 nm) decrease or by increase in percent phase dark spores viewed under phase contrast microscopy. Strict anaerobic conditions were maintained throughout the study. As the concentration of each chemical was increased the rate of germination or growth decreased. This occurred for each pH tested. GHA, BHT, TBHQ and 8-0HQ were more effective inhibitors of growth and germination as the pH was lowered from 7.2 to 5.7. At pH 7.2 50 µg/ml BHA, 200 µg/ml TBHQ and 200 µg/ml 8-0HQ were the minimum concentrations necessary for 90% inhibition of germination. BHT (400 µg/ml) inhibited germination by 65% at pH 7.2. Minimum concentrations at which growth at. pH 7.2 was inhibited by 95% were 60 µg/ml BHA, 20 µg/ml BHT, 250 µg/ml TBHQ and 20 µg/ml 8-0HQ. Inhibition of growth and germination by each chemical was found to be reversible with the exception of the inhibition of growth by BHT. / M.S.

The thesis examined McMaster University undergraduates’ beliefs about health and contagion, and their implication for antibacterial soap use. A qualitative methodology was used and 30 participants were interviewed, and the transcripts coded and analysed for emergent themes. Students understand health in terms of having energy, being disease free, and as something to be achieved through healthy lifestyle choices and cleanliness. These beliefs form an explanatory model of health that has several key components used to make health decisions, including using or not using antibacterial soap. The participants see their health as continually threatened by sources of illness. Contagion is one of the principal threats identified and understood as transmitted through the air, or on the surfaces of contaminated people and objects. Two modes of defence were articulated in the interviews. Internal components of defence involve maintaining immune rigour; external components drives activities such as personal hygiene and cleaning to protect against pathogens. Men tend to have a more internally focussed explanatory model of health, while women have a more external focus. This seems to explain why the women in this study were eight times more likely to use antibacterial soap than the men, a finding that was statistically significant (p=.O27). Social values are expressed through the explanatory model, including social boundaries and morality. The model also aligns very well with the biomedical paradigm in that it reduces health to its physical components, provides a mechanistic explanation of the body, and separates mind and body as discrete entities and as an object of control. Biomedicine seems to be broadening into new social domains, such as gender, social boundaries and morality, which are also reflected in students' beliefs about health. / Thesis / Master of Arts (MA)

The objective of this study was to determine the pharmacokinetics and tolerance of tulathromycin (Draxxin®; 2.5 mg/kg once) after intramuscular (IM), subcutaneous (SC), and slow intravenous (IV) administration to six adult horses. A three-phase design and 4-week washout period were used. Drug concentrations in blood and bronchoalveolar lavage (BAL) samples were determined by ultra-performance liquid chromatography tandem mass spectrometry and pharmacokinetic parameters calculated using noncompartmental analysis. Following SC and IM administration, all horses exhibited sweating, discomfort, and periods of recumbency. As signs were more severe after SC administration this route was only used in 3/6 horses. Intravenous administration of tulathromycin was well tolerated in all horses. Mean bioavailability was 99.4% IM and 115% SC. Mean maximum plasma concentration was 645 ng/ml IM and 373 ng/ ml SC. Mean half-life was 59.8 h, 54.8 h, and 57.9 h for IV, IM, and SC administration, respectively. Mean clearance was 3.25 ml/kg/min, and mean volume of distribution was 16.8 L/kg following IV administration. Drug was detectable in plasma and BAL samples for 120 h following all routes; however, adverse effects may prevent IM use and SC use is not recommended. Tulathromycin may be a practical and affordable antibacterial for use in adult equine patients. / Master of Science / In human and veterinary medicine, antibacterial drugs are a mainstay of treatment. Antibacterials have been used for almost 100 years to prevent microbial organism infection, and as a treatment once there is an established infection. Although there are multiple "classes" of antibacterials that have different spectrums of activity and mechanisms of action, antibacterial resistance has become increasingly prevalent over time. The increasing rate of antimicrobial resistance has led to recommendations that medical practitioners be more judicious in the use of these drugs and to prescribe antibacterials to patients only when necessary. In equine medicine, once an antibacterial is deemed necessary, there are additional considerations, including administration method, frequency of administration, and availability and cost of antibacterial drugs. Tulathromycin, a long-acting semi-synthetic macrolide, is an antibacterial that is approved for use in cattle and swine and may have utility for equine patients for a variety of conditions. This study in healthy adult horses demonstrated that tulathromycin was detectable in plasma and the respiratory tract for up to 5 days after single dose administration. Thus, tulathromycin may be a practical and affordable antibacterial for use in equine patients.

Complications during the healing process of skin wounds often arise due to infection by pathogenic bacteria. Bacterial hydrolytic enzymes degrade the host tissue while biofilms can shield the bacterial cells from the host's immune response. Wound dressings with bacteriostatic or bactericidal properties are a promising solution. This study investigated the potential of surface acetylated bacterial cellulose as a novel antibacterial wound dressing. Hydroxyl groups on the surface of bacterial cellulose were substituted with acetyl groups using acetic anhydride in a citric acid-catalyzed reaction. The resulting ester linkages between the acetyl groups and bacterial cellulose surface were hypothesized to be cleaved by bacterial esterases or other hydrolytic enzymes such that acetic acid, a well-known antibacterial compound, will be produced leading to the death of the bacterial cells. Surface acetylation was confirmed via FTIR and its effect on the morphology of bacterial cellulose was analyzed with FESEM and XRD while the degree of substitution was determined by HPLC-UV. Indirect contact human cell cytotoxicity assays using extracts from surface acetylated bacterial cellulose showed no cytotoxic effect on human umbilical vein endothelial cells. Two types of antibacterial assays were performed in which surface acetylated bacterial cellulose was exposed to Staphylococcus epidermidis, Escherichia coli, and Pseudomonas aeruginosa which were selected as model bacteria for Gram-positive, Gram-negative, and pathogenic bacterial species, respectively. Neither assay showed a reduction of bacterial cell viability. Further research is needed to determine if the acetyl ester linkages on the surface of bacterial cellulose are susceptible to cleavage by bacterial esterase enzymes. / Master of Science / The healing of skin wounds is frequently complicated by infection of the wound with harmful bacteria. A potential remedy could be wound dressings that kill such bacteria. Bacterial cellulose is a naturally occurring biomaterial with multiple properties that make it an ideal material for wound dressings. Pure bacterial cellulose has no inherent antibacterial properties but can be chemically modified with a separate substance that is antibacterial such as acetic acid. This study investigates the potential of chemically modified bacterial cellulose in antibacterial wound dressing applications. The material may release acetic acid in the presence of bacteria and cause cell death. A series of human cell and antibacterial assays were carried out to test the ability of the modified bacterial cellulose to inhibit bacterial growth as well as any potential harmful effect on human cells. While it showed no adverse effects on human cells, the modified bacterial cellulose did not reduce bacterial cell viability.