京都大学 / 新制・課程博士 / 博士(社会健康医学) / 甲第24290号 / 社医博第126号 / 新制||社医||12(附属図書館) / 京都大学大学院医学研究科社会健康医学系専攻 / (主査)教授 今中 雄一, 教授 西浦 博, 教授 寺田 智祐 / 学位規則第4条第1項該当 / Doctor of Public Health / Kyoto University / DFAM

The study explored the prevalence of biofilm formers and its association with multidrug resistance in Klebsiella Pneumonia, a gram-negative bacterium that has high propensity to form antibiotic resistant strains and forms biofilms. Biofilms are complex microbial community with attributes that vary from planktonic cells. Antibiotic resistance is a property that has shown evidence to be higher in biofilms as compared to planktonic cells. Multi-drug resistance, a higher form of antibiotic resistance, is defined as resistance to at least one agent in three or more antibiotic categories. A single-armed and a two-armed meta-analysis was done to assess prevalence of biofilm formers and to find association between biofilm formation capacity and multi drug resistance. The one-armed meta-analysis revealed 74% (95% CI: 64%-83%) prevalence of biofilm formers among clinical isolates of Klebsiella Pneumonia. The prevalence rate is comparable with that of prevalence rate attained by other bacterium by similar meta-analysis studies. This high prevalence of biofilm formers warrants for a paradigm shift in treatment strategies for treatment of infections. The two-armed meta-analysis showed that there was identical risk of multi drug resistance among the biofilm formers and non-biofilm formers. The result challenges the intrinsic capacity of planktonic cells to resist against antibiotics to achieve multi drug resistance. Further research to update the biofilm formation profiles and to understand the resistance mechanism in commonly occurring bacterial infections in of utmost importance.

Avian pathogenic Escherichia coli (APEC) is the causative agent of colibacillosis. APEC causes significant economic losses to the poultry industry. In this study, 66 E. coli isolates were collected from broiler flocks across Mississippi and categorized as clinical and non-clinical isolates. Genotypic and phenotypic characterization of virulence factors and antimicrobial resistance profiles of these E. coli were examined. The data disclosed a higher prevalence of virulence genes in clinical isolates than in non-clinical isolates. High differences on the genotypic and phenotypic antimicrobial resistance among clinical and non-clinical isolates were observed. Whole genome sequences of avian E. coli elaborated a diverse range in genetic composition, phylogenic relationship, antimicrobial resistance, and virulence gene profiles. Collectively, the results showed that the virulence factors and phenotypic characteristics of APEC may play a role in the pathogenesis of avian colibacillosis. Therefore, this study provides insight to understand the epidemiological background, microbial behavior, and pathogenesis of APEC.

The rise of antimicrobial resistance demands the development of more rapid screening methods for the detection of antimicrobial resistance in clinical samples to both give the patient the proper treatment and expedite the treatment of patients. Cerium oxide nanoparticles may serve a useful role in diagnostics due to their ability to exist in a mixed valence state and act as either oxidizing agents or reducing agents. Considering that cerium oxide nanoparticles have been shown to shift in absorbance upon oxidation, a useful method of antimicrobial resistance detection could be based on the oxidation of cerium oxide nanoparticles. Herein, an assay is described whereby cerium oxide nanoparticle oxidation is a function of glucose metabolism of bacterial samples in the presence of an antimicrobial agent. Cerium oxide nanoparticles were shown to have an absorbance in the range of 395nm upon oxidation by hydrogen peroxide whereas mixed valence cerium oxide nanoparticles lacked an absorbance around 395nm. In the presence the hydrogen peroxide-producing glucose oxidase and either increasing concentrations of glucose or bacterial medium supplemented with increasing concentrations of glucose, cerium oxide nanoparticles were shown to increase in absorbance at 395nm. This oxidation assay was capable of measuring differences in the absorbance of E. coli and S. aureus samples grown in the presence of inhibitory and non-inhibitory concentrations of ampicillin in as little as six hours. Therefore, this cerium oxide nanoparticle oxidation assay may be very useful for use in clinical laboratories for the detection of antimicrobial resistance due to the relatively low cost, no requirement for specialized equipment and, most importantly, the reduced incubation time of the assay to as little as six hours compared to current gold standard antimicrobial resistance detection methods that require 24 hours.; This assay may thus also help partially circumvent the issue of knowledge of antimicrobial resistance in infected patients before prescribing improper regimens.

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