Bacterial resistance to antibiotics has increased rapidly within recent years, and it has become a serious threat to public health. Infections caused by multi-drug resistant bacteria entail higher morbidity, mortality, and a burden to health care systems. The use of biocides, including silver compounds, may affect the resistance to both biocides and antibiotics and, thereby, can be a driving factor in this development. The aim of the following thesis was to investigate the frequency of silver resistance and the effects of silver exposure on bacterial populations being of clinical significance and from geographically different parts of the world. Furthermore, it explored the genetic background of silver resistance, and if silver could select directly or indirectly for antibiotic resistance. By a range of methods, from culture in broth to whole genome sequencing, bacterial populations from humans, birds and from the environment were characterized. The studies showed that sil genes, encoding silver resistance, occurred at a high frequency. Sil genes were found in 48 % of Enterobacter spp., in 41 % of Klebsiella spp. and in 21 % of all human Escherichia coli isolates with production of certain types of extended-spectrum beta-lactamases (CTX-M-14 and CTX-M-15). In contrast, silver resistance was not found in bird isolates or in bacterial species, such as Pseudomonas aeruginosa and Legionella spp., with wet environments as their natural habitat. One silver-resistant Enterobacter cloacae strain was isolated from a chronic leg ulcer after only three weeks of treatment with silver-based dressings. The in-vivo effects of these dressings were limited, and they failed to eradicate both Gram-positive and Gram-negative bacteria. The activity of silver nitrate in vitro was bacteriostatic on Gram-positive species such as S. aureus and bactericidal on Gram-negative species. In Enterobacteriaceae, sil genes were associated with silver resistance phenotypes in all but one case. Using whole genome sequencing, single nucleotide polymorphisms in the silS gene were discovered after silver exposure in isolates with expressed silver resistance. This resistance could co-select for resistance to beta-lactams, co-trimoxazole and gentamicin. The findings of this thesis indicate that silver exposure may cause phenotypic silver resistance, and it may reduce the susceptibility to mainly beta-lactams and select for bacteria with resistance to clinically important antibiotics.

Antimicrobial resistance (AMR) poses a substantial threat to public health and clinical medicine. By 2050, it’s predicted that AMR will be responsible for a yearly mortality rate of 10 million people, surpassing the mortality of cancer. Despite this daunting future we face, there are many efforts currently employed to combat the growth of AMR. One significant effort involves surveillance and early identification of novel resistant bacteria circulating in high antibiotic exposure environments. The second chapter of this thesis focuses on sampling 25 patients from a hospital environment, rich with antibiotics, to build a collection of AMR bacteria that will be tested and added to surveillance efforts/future study. This chapter allowed for the identification of several worrying AMR bacteria that provide greater insights into circulating AMR in Canadian hospitals and their patients. From the AMR collection created in chapter 2, we are also able to advance our scientific understanding of how antibiotic resistance develops within us and causes issues with treatment. In chapter 3, we looked at the effects of antibiotic administration routes on the level of AMR observed in our patient sample. We saw that current approaches to limit selection for AMR in the gut still resulted in clinically significant and concerning increases in AMR. Furthermore, this chapter allowed greater understanding of contributors to increased AMR in patients. AMR increases are not fully explained by exposure/colonization in hospital settings, but also by evolution of AMR originating from non-resistant bacteria in the gut. Additionally, analysis of these bacteria will inform expected AMR evolutionary trajectories and help us plan against them. During analysis of patient data, we also came across evolution of a less understood resistance phenotype, hetero-resistance, to a very important antibiotic, colistin. We investigated a commonly prescribed antifungal, fluconazole, for its ability to promote this resistance phenotype; however, it appeared that fluconazole did not promote this phenotype. Ultimately, this thesis serves as a valuable reservoir of AMR bacteria for future study and contributes to a greater understanding of AMR development in patients, one day leading to more informed clinical decision making. / Thesis / Master of Science (MSc)

published_or_final_version / Community Medicine / Master / Master of Public Health

No description available.

Blackleg caused by Leptosphaeria maculans (Desm.) Ces. & De Not. is one of the most serious diseases in canola production. A high level of blackleg resistance has been shown in Brassica carinata A. Braun (BBCC) and new synthetic hexaploid Brassica species (AABBCC) developed from the crosses of B. rapa L. and B. carinata. Blackleg resistance from B. carinata and hexaploid Brassica accessions was transferred into B. napus L. using interspecific hybridization followed by backcrossing to a susceptible B. napus cultivar ‘Westar’ three or four times and selfing one or two times to produce pure lines. Leptosphaeria maculans isolate 03-15-03 was used to select the resistant plants in each generation using cotyledon inoculation, and four L. maculans isolates (03-15-03, 3-42-6, 09stonewall9553, and PG4-1-M) were utilized in advanced generations. In the cross of B. napus ‘Westar’ and B. carinata, all plants in the F1 showed a high level of resistance to L. maculans isolate 03-15-03. According to the chi-square testing for goodness of fit, the segregation of resistant and susceptible plants fit a 1:1 ratio in the BC1, BC3, and BC4. In the BC3F2, two families followed a 3:1 segregation ratio of resistant and susceptible plants. The results suggest that the resistance to L. maculans transferred from B. carinata into canola ‘Westar’ was controlled by a single locus. Embryo rescue tissue culture was used to obtain F1 plants of the crosses of ‘Westar’ and synthetic hexaploid Brassica accessions. In the BC1 and BC2, most families did not fit a 1:1 segregation ratio of resistant and susceptible plants. The segregation of resistant and susceptible plants fit a 3:1 ratio when inoculated with L. maculans isolates in the BC1F2-3.1.1s and BC1F3-3.1.1.1ss families. Meanwhile, the BC2-3.1.1 family also followed a 1:1 segregation of resistant and susceptible plants inoculated with L. maculans isolate 03-15-03. The results suggest that the resistance to L. maculans introgressed from synthetic hexaploid Brassica species into B. napus is most likely controlled by a single locus. / May 2016

This paper outlines interview based, qualitative research that was conducted with six male youth who were previously students in my Social Studies 11 class. Within two separate, semi-structured interviews, participants were asked to discuss student resistance to anti oppressive pedagogy that focused on gender, and their understanding of masculinities. The initial purpose of this research was to find a relationship, if any, between acts of student resistance and the construction of masculinities. Participant perceptions of masculinities evolved as the dominant theme within the interviews. These discussions revealed that student understandings of masculinity were often entrenched in hegemonic language, yet contradictions were exposed between their rote definitions and personal narratives. Further, the use of media as a discourse became a venue for complicating essentialist understandings of masculinity, and for exposing multiple, fluid, versions of masculinities. Within these discussions of multiplicity, race and sexuality became two intersections of identity that took precedence. Also the intersection of teacher identity and the reading of identity terms emerged as a salient interpretation for gender discussions in the classroom. Throughout this write-up of the research are methodological considerations surrounding power, the construction of masculinity and race, and the further entrenching of heteronormativity, in the form of methodological interludes. Finally, within the conclusion, I consider the implications for practice and future directions for research in masculinities.

In 2002, West Nile virus was isolated for the first time in Harris County, Texas. The subsequent epidemic led the Harris County Mosquito Control Division to initiate an extensive spraying operation to suppress infected adult mosquitoes. The control program was aimed at the predominate disease-carrying mosquito for the southern United States, Culex quinquefasciatus Say. With the increase of insecticide pressure on the mosquito populations, the possibility of resistance was brought into question. A three year study using a vial bioassay test was conducted in Harris (2004-2005) and Brazos (2005-2006) counties to determine the resistance status of Cx. quinquefasciatus to the six chemicals (malathion, naled, resmethrin, permethrin, sumithrin, and pyrethrum) used most frequently in adult mosquito control programs. The resistance ratios acquired from the vial bioassay tests were mapped onto shapefiles for Harris and Brazos counties, which revealed clustering of areas with pyrethroid resistance mosquito populations in the northeastern, southeastern, and southwestern corners of Loop 610 in Harris County. An additional six-month preliminary study, involving six operational areas in Harris County and three in Brazos County, was conducted, demonstrating only minor fluctuations in the monthly resistance ratios occurring in both counties in 2005. A significant correlation was documented between the two years of resistance ratios for mosquitoes to the three pyrethroids in Harris County and all the insecticides except pyrethrum in Brazos County. A significant relationship was also found between the resmethrin resistance ratios and the number of spray events performed during the previous year and the malathion resistance ratios with the insecticide treatments conducted in the same year. The correlation analyses provide data used to predict areas where resistance can develop in the mosquito population, thus providing the control agency more data to plan future control tactics. The overall analysis indicated that Harris County has localized pockets of resistant mosquitoes; but, on a whole, it does not seem to have widespread resistance in its mosquito populations. The only resistance that was detected was in the mosquitoes tested against the three pyrethroids. Mosquitoes in Brazos County, which has no organized mosquito control, demonstrated county-wide susceptibility to all six insecticides tested.

Thesis (doctoral)--Friedrich-Wilhelms-Universität zu Berlin, 1882. / Vita.

Insect pests of public health importance were the first among which the development of highly insecticide resistant strains was shown to be widespread. More recently, numerous instances of resistance among economically important insect pests of growing crops have been revealed. The relative scarcity of reported resistance in stored-products pests is probably a reflection of fewer investigations and fewer instances of continued insecticidal controls. The possible development of resistance at a future date in stored-products pests and the chance that one might avoid such development if it can be foreseen should be adequate justification for the present investigation. It was felt that the occurrence of stored-products pests as isolated islands of population might enhance the selection of resistant strains locally and also allow their eradication if they are discovered, making this a worthwhile area for study. [...]

This paper outlines interview based, qualitative research that was conducted with six male youth who were previously students in my Social Studies 11 class. Within two separate, semi-structured interviews, participants were asked to discuss student resistance to anti oppressive pedagogy that focused on gender, and their understanding of masculinities. The initial purpose of this research was to find a relationship, if any, between acts of student resistance and the construction of masculinities. Participant perceptions of masculinities evolved as the dominant theme within the interviews. These discussions revealed that student understandings of masculinity were often entrenched in hegemonic language, yet contradictions were exposed between their rote definitions and personal narratives. Further, the use of media as a discourse became a venue for complicating essentialist understandings of masculinity, and for exposing multiple, fluid, versions of masculinities. Within these discussions of multiplicity, race and sexuality became two intersections of identity that took precedence. Also the intersection of teacher identity and the reading of identity terms emerged as a salient interpretation for gender discussions in the classroom. Throughout this write-up of the research are methodological considerations surrounding power, the construction of masculinity and race, and the further entrenching of heteronormativity, in the form of methodological interludes. Finally, within the conclusion, I consider the implications for practice and future directions for research in masculinities.