Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 157-164).

No description available.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 155-163).

Thesis (Ph. D.)--University of Washington, 2000. / Vita. Includes bibliographical references (leaves 161-171).

MSc (Med), Clinical Microbiology and Infectious Diseases, Faculty of Health Sciences, University of the Witwatersrand / The goal of infection control is to minimize the risk of exposure to potential pathogens and to create a safe working environment in which patients can be treated. Use of disinfectants in is an integral part of infection control. The rate of killing of microorganisms depends upon the type, concentration and time of exposure of the killing agent (disinfectant). Chlorinated compounds are frequently used in healthcare settings but chlorine dioxide has only been used in industries on a large scale. Aseptrol® is newly developed slow release chlorine dioxide and noncorrosive formula which can be used on a smaller scale basis. This study assessed the antimicrobial properties of Aseptrol® (48ppm and 24ppm) in comparison with previously used sodium dichloroisocyanurate containing formula, Presept® (10 000ppm). Both disinfectants killed more susceptible bacteria, such as Staphylococcus aureus, Pseudomonas. aeruginosa and Streptococcus mutans within 30 seconds and proved to be fungicidal by killing Candida albicans within 30 seconds. Aseptrol® and Presept® killed less susceptible mycobacteria such as Mycobacterium tuberculosis, Mycobacterium avium subsp. avium and blood borne organism Hepatitis B virus within 30 seconds. Highly resistant B. subtilis spores were killed in 2 and 2.5 minutes by Aseptrol® and Presept® respectively. Although manufacturers recommend that the disinfectant solutions should be prepared daily, when the shelf-life of prepared solutions stored in screw cap bottles was studied, the results showed that Aseptrol® can be effectively used for 27 day and Presept® for more than 37 days. The goal of infection control is to minimize the risk of exposure to potential pathogens and to create a safe working environment in which patients can be treated. Use of disinfectants in is an integral part of infection control. The rate of killing of microorganisms depends upon the type, concentration and time of exposure of the killing agent (disinfectant). Chlorinated compounds are frequently used in healthcare settings but chlorine dioxide has only been used in industries on a large scale. Aseptrol® is newly developed slow release chlorine dioxide and noncorrosive formula which can be used on a smaller scale basis. This study assessed the antimicrobial properties of Aseptrol® (48ppm and 24ppm) in comparison with previously used sodium dichloroisocyanurate containing formula, Presept® (10 000ppm). Both disinfectants killed more susceptible bacteria, such as Staphylococcus aureus, Pseudomonas. aeruginosa and Streptococcus mutans within 30 seconds and proved to be fungicidal by killing Candida albicans within 30 seconds. Aseptrol® and Presept® killed less susceptible mycobacteria such as Mycobacterium tuberculosis, Mycobacterium avium subsp. avium and blood borne organism Hepatitis B virus within 30 seconds. Highly resistant B. subtilis spores were killed in 2 and 2.5 minutes by Aseptrol® and Presept® respectively. Although manufacturers recommend that the disinfectant solutions should be prepared daily, when the shelf-life of prepared solutions stored in screw cap bottles was studied, the results showed that Aseptrol® can be effectively used for 27 day and Presept® for more than 37 days. Chlorinated disinfectants, such as Aseptrol® and Presept®, have potential to be used as intermediate to high level disinfectants in medical and dental settings, where above test organisms are primary contaminants. It is also possible to use them as sterilants, where semicritical conditions are required. Aseptrol® has an additional advantage because it is noncorrosive and can be used on metal instruments.

No description available.

Biomaterial-associated infections remain a significant complication of medical implants. Of the different strains of bacteria associated with nosocomial infections, 70% are resistant to at least one of the drugs used for treatment (Bren 2002). In 2000 the Center for Disease Control ranked microbial agents as the 4th leading actual cause of death in the United States of America (Mokdad et al. 2004).In an effort to improve the prevention and treatment of infections, this research has three objectives: the development of an alternative sterilization method for medical devices; assessing a new antimicrobial material for the prevention of infections in situ; and assessing mechanisms of acquired microbial resistance. The biocide being investigated in this body of work is chlorine dioxide gas.While multiple sterilization methods are available, there are limitations to all of these technologies. For example, chemical sterilization can leave residues on the surface of the material. These residuals can be toxic, causing sensitization reactions when the materials are implanted in the body (Dolovich et al. 1984; Marshall et al. 1985; Chapman et al. 1986; Dolovich et al. 1987). Research has shown that materials sterilized with increasing concentrations of the chemical sterilizing agent have increasing quantities of residuals (Lyarskii et al. 1984). The studies presented here will ascertain the environmental parameters required for sterilization of biomaterials with low concentrations of chlorine dioxide gas and assess polymers sterilized using these conditions for the cytotoxicity of possible chemical residuals.Investigations into preventing biomaterial-based infections in situ have focused on changing the biomaterial properties. Materials with altered physicochemical characteristics to prevent bacterial adhesion have been developed, and antibiotics and silver have been incorporated into the biomaterials to inhibit bacterial colonization. Unfortunately, the rapid depletion of incorporated antimicrobial agents, altered bactericidal activity in vivo, and the development of antibiotic resistance, have all limited the effectiveness of current technologies. In these studies a chlorine dioxide generating material was assessed using in vitro and in vivo assays.While assessing the bactericidal efficacy of a selection of chlorine dioxide generating materials, a spontaneous bacterial mutant with a reduced susceptibility to chlorine dioxide was isolated. The final section of this work will investigate a potential mechanism of resistance to chlorine dioxide.

Thesis (M.Sc.)(Microbiology)--University of Pretoria, 2006. / Includes summary. Includes bibliography. Available on the Internet via the World Wide Web.

Thesis (Ph. D.)--University of Washington, 2001. / Vita. Includes bibliographical references (leaves 168-177).

Non-typhoidal Salmonella enterica serovars continue to be the leading cause of foodborne illnesses in United States. Chlorine, chlorine related, and quaternary compounds are generally used for disinfecting carcasses and equipment in processing industries. The current study was aimed at understanding the inactivation kinetics of four Salmonella serovars to chlorine, chlorine dioxide and cetylpyridinium chloride (CPC). The transcriptomic responses to oxidative stress was investigated in stationary and log phase cells of S. Typhimurium. The study was also aimed at understanding the effect of the chemicals on the expression of virulence genes associated with the Salmonella Pathogenecity Island 1 (SPI1). The possible induction of the viable but nonculturable (VBNC) state in Salmonella due to CPC was also investigated. The inactivation parameters for each serovar and the chemical were estimated based on the Hom's model, ln (N/N0) = -k C^n T^m and it appeared that while disinfectant contact time was significant, biocide concentration in the overall disinfection was insignificant. This was true especially for chlorine and CPC with subtle differences observed between the serovars. The inactivation efficacy was, however, dependent on both concentration and the exposure time for chlorine dioxide. The highest degree of inactivation was obtained with chlorine followed by chlorine dioxide and CPC. Transcriptomic responses of S. Typhimurium revealed significant downregulation of several metabolic processes such as tricarboxylic acid cycle, oxidative phosphorylation, and amino acid biosynthesis in both log and stationary phase cells. Several stress related genes such as usp, rpoS and ompR were upregulated in the stationary phase cells. Majority of the virulence genes associated with the SPI1 were found to be downregulated for all the treatments. While treatment with chlorine and CPC caused downregulation of all the virulence genes, treatment with chlorine dioxide caused significant upregulation of few (hilC, invC, sipA and sipB) genes associated with the SPI1. Finally, the induction of VBNC state was not concluded as a result of treatment with CPC. However, significant percentage of cells (45 percent) with intact membrane was established based on the BacLight assayTM.