Theses and Dissertations at Montana State University (MSU)
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Item NMR hydrophilic metabolomic analysis of bacterial resistance pathways using multivalent quaternary ammonium antimicrobials in Escherichia coli and Bacillus cereus exposed to DABCO and mannose functionalized dendrimers(Montana State University - Bozeman, College of Letters & Science, 2021) Aries, Michelle Lynne; Chairperson, Graduate Committee: Mary J. Cloninger; This is a manuscript style paper that includes co-authored chapters.Novel antibiotics developed using a new scaffold are needed to combat the rising tide of antibiotic resistant bacteria. Multivalent antibiotics are a relatively new approach that have the potential to greatly increase the efficacy of antibiotics while making it difficult for bacteria to develop resistance. Dendrimers are an attractive framework for the multivalent presentation of antibacterial moieties. Quaternary ammonium compounds (QAC) are a positively charged class of membrane disruptors that are attracted to the large negative charge on phospholipid membranes. Nuclear magnetic resonance (NMR) metabolomics is a quantitative method used for comparison of metabolic profiles of wild type and mutated bacterial samples, enabling the study of bacterial response to antimicrobials. Proton (1 H) NMR hydrophilic metabolomics was used to study gram-negative and gram-positive bacteria upon exposure to 1,4-diazabicyclo-2,2,2-octane (DABCO) with a 16-carbon chain tethered onto a mannose functionalized poly(amidoamine) (PAMAM) dendrimer (denoted as DABCOMD), a membrane disrupting multivalent QAC. Stock Escherichia coli (E. coli) (denoted as wild type) and DABCOMD mutated E. coli (denoted as mutants) were collected in the mid log and stationary phases. The same procedures were used for Bacillus cereus (B. cereus) as for E. coli samples (denoted as unchallenged), except that a DABCOMD challenged sample set was added (denoted as challenged). The challenged sample set procedures were identical to the unchallenged, except DABCOMD was included at 33 % of the MIC value in the growth media for growth curve acquisition and sample collection. The greatest differences observed between the metabolic profiles of the wild type and mutated E. coli samples and between the challenged and unchallenged B. cereus samples were in energy-associated metabolites and membrane-related pathways. The mutants in all sample types were associated with higher levels of spent energy molecules (including AMP and NAD+) and peptidoglycan related compounds (including N-acetylglucosamine). Overall, more changes were observed for B. cereus (gram-positive), especially in challenged mutant B. cereus samples, than for E. coli (gram-negative) samples. Since DABCOMD is a positively charged multivalent membrane disruptor, both B. cereus and E. coli mutated to garner protection by altering their peptidoglycan layer composition, which is energetically costly.Item Antibiotic use and acquired bacterial resistance(Montana State University - Bozeman, College of Nursing, 1996) Hollis, Brett Roy; Chairperson, Graduate Committee: Mary K. Dempsey-NoreikaItem Antibiotic penetration through Pseudomonas aeruginosa colony biofilms(Montana State University - Bozeman, College of Engineering, 2001) Walters, Marshall Charles, IIIItem Role of transport limitation in the resistance of Pseudomonas aerunginosa biofilms to ciprofloxacin and levofloxacin(Montana State University - Bozeman, College of Engineering, 1996) Vrany, Julia DawnBacterial biofilm infections are often far less susceptible to antibiotic therapy than their planktonic, or freely suspended counterparts. Transport limitation of the antibiotic within the biofilm has been proposed as one explanation for this resistance. To explore the possibility that transport limitation contributes to a decreased antibiotic efficacy, a Comparison was made between the efficacies of two fluoroquinolone antibiotics, ciprofloxacin and levofloxacin, against freely suspended and biofilm bacteria. Transport of the antibiotics to the biofilm-substratum interface was monitored using ATR-FTIR spectroscopy techniques. Both biofilms and planktonic organisms were treated with antibiotic concentrations of 100, 250, and 500 μg ml-1 for 30 min and rinsed for 1 h with fresh media. Antibiotic efficacy was determined by the ratio of culturable bacteria to total cell counts. The experimental ATR-FTIR transport data was then simulated with a mathematical computer model containing the processes of molecular diffusion, adsorption, and desorption to provide possible explanations for differences in antibiotic delivery. Levofloxacin was found to be more efficacious against planktonic organisms than biofilm cells. However, no difference in efficacy was seen when planktonic and biofilm bacteria were treated with ciprofloxacin. ATR-FTIR results showed that the biofilm provided very little transport limitation for each antibiotic, thus suggesting that the reduced susceptibility of a biofilm to antimicrobial treatment may be due to factors other than transport.Item Spatial heterogeneity in Pseudomonas aeruginosa biofilms and how it affects antibiotic tolerance(Montana State University - Bozeman, College of Engineering, 2006) Richards, Lee Alexander; Chairperson, Graduate Committee: Philip S. StewartThis dissertation presents evidence of heterogeneity within Pseudomonas aeruginosa biofilms and the effects of said heterogeneity on antibiotic tolerance. The existence of oxygen concentration gradients within the biofilm was confirmed. There were in fact regions within the biofilm that were nearly anoxic, this was confirmed by use of dissolved oxygen microelectrodes. The size of the aerobic zone within the biofilm agreed with the size of the active zone indicated by the use of an inducible green fluorescent protein. We found that anoxia could explain some of the biofilm's recalcitrance to the antibiotics ciprofloxacin and tobramycin, but the effects of anoxia were not adequate to explain all of an intact biofilm's tolerance to antimicrobial treatment. It was also apparent that glucose limitation was not a factor in biofilm recalcitrance. In addition, dormancy within Pseudomonas aeruginosa biofilms was explored by use of a novel approach to labeling active and dormant cells within the biofilm using a strain of P. aeruginosa tagged with a stable, inducible, green fluorescent protein. Spatial patterns of activity were visualized by microscopy. Further, we found it possible to sort the active and dormant cells using a flow cytometer. It was thus possible to determine the relative viability of each population after treatment with the antibiotics tobramycin and ciprofloxacin. We found that dormant cells were much more tolerant to antibiotic treatment than were active cells within the same biofilm.Item Factors affecting medical-surgical area nurses' compliance with contact precautions(Montana State University - Bozeman, College of Nursing, 2009) Eby, Anne Kathryn; Chairperson, Graduate Committee: Christina Sieloff; Clementine Rice (co-chair)Multidrug-resistant organisms are a significant threat in health care facilities, and are associated with many adverse consequences for infected patients. However, despite these concerns and the evidence that contact precautions are an effective way to address them, compliance with contact precautions guidelines among health care workers remains low (Farr, 2000). The primary goal of this study was to examine factors affecting medical-surgical nurses' compliance with contact precautions guidelines when caring for patients colonized by or infected with multidrug-resistant organisms. A secondary purpose of this study was to describe demographic characteristics of medical-surgical nurses to determine if certain characteristics (e.g. age, time in practice, level of education) had a relationship with their compliance in using contact precautions guidelines. Finally, this study examined barriers to the use of contact precautions and consequences for failure to follow contact precautions guidelines. A survey tool was developed by the researcher for this study to examine these questions, and an exploratory, cross-sectional, correlation descriptive study was conducted. The study group was made up primarily of female nurses with associate or bachelor degrees. Nurses from the orthopedic and neurosurgery unit made up the largest percentage of respondents. All respondents indicated that they were familiar with CP guidelines. Eight primary barriers to the use of contact precautions were listed by participants. Half of the participants listed one of the time management categories ("no time" or "urgency") as the primary barrier to compliance with contact precautions. Participants' age, years experience and level of education were not statistically significant predictors of the participants' level of compliance. There was not a statistically significant difference between the barriers to compliance groups (no time/urgency versus other) on their ability to comply with contact precautions. Lastly, there was not a statistically significant relationship among the primary consequence of non-compliance with CP guidelines (medical versus other) and the participants' level of compliance (low versus high).