Epidemiological and Molecular Investigations on Antibiotic Resistance in Group B Streptococcus and Escherichia coli.
dc.contributor.author | Dang, Trang Nguyen Doan | en_US |
dc.date.accessioned | 2012-10-12T15:33:14Z | |
dc.date.available | 2012-10-12T15:33:14Z | |
dc.date.issued | 2012 | en_US |
dc.date.submitted | 2012 | en_US |
dc.identifier.uri | https://hdl.handle.net/2027.42/94083 | |
dc.description.abstract | Antibiotic resistance is currently one of the greatest challenges to clinicians and to public health. The detection of resistance mechanisms to antibiotics has become more and more epidemiologically and clinically important. This dissertation investigates rates, mechanisms of antibiotic resistance and adaptation in Group B Streptococcus (GBS) and Escherichia coli by the combined power of epidemiologic principles and molecular methods. In chapter 3 and 4, I describe the rates and mechanisms of resistance to fluoroquinolones in GBS. My colleagues and I report a strikingly high frequency of resistance to different fluoroquinolones, especially to norfloxacin (~93%) among a collection of 1075 GBS strains isolated from South Korea between 2006 and 2008. Ciprofloxacin and levofloxacin resistance was higher in invasive than in colonizing GBS isolates (10.6% versus 2.5% (p < 0.001) in ciprofloxacin resistance, 9.8% versus 2.1% (p < 0.001) in levofloxacin resistance). Mutations in gyrase and topoisomerase were found to be the resistance mechanism to ciprofloxacin, levofloxacin and moxifloxacin while efflux pumps appear to be the predominant resistance mechanism among GBS strains resistant to only norfloxacin. Strain serotypes were not associated with susceptibility to fluoroquinolones. In chapter 5, I turn my attention to Escherichia coli adaptation measured by differences in antibiotic resistance and in the distribution of CRISPRs (Clustered Regularly Interspaced Short Palindromic Repeats) between commensal E. coli and uropathogenic E. coli (UPEC) isolates. Recently, CRISPRs were identified as an immune system protecting numerous bacteria against invasion by phages, plasmids or other forms of foreign DNA. In my study on 81 matched pairs of commensal E. coli and UPEC strains isolated from UTI women, commensal E. coli isolates were found to have more repeats (p = 0.009) and more unique spacers (p < 0.0001) than UPEC isolates. Additionally, UPEC isolates were more likely to be resistant to the antibiotics tested (cefazolin (p < 0.0001), trimethoprim/sulfamethoxazole (p = 0.05)) than commensal E. coli isolates. Association between CRISPRs and antibiotic resistance was not well identified in this study. These findings support the hypothesis of better adaptability of UPEC and are suggestive of the positive role of E. coli CRISPRs as a defense system. | en_US |
dc.language.iso | en_US | en_US |
dc.subject | Mechanisms of Antibiotic Resistance to Fluoroquinolones in Group B Streptococcus | en_US |
dc.subject | CRISPR Distribution and Association With Uropathogenicity and Antibiotic Resistance in Escherichia Coli | en_US |
dc.title | Epidemiological and Molecular Investigations on Antibiotic Resistance in Group B Streptococcus and Escherichia coli. | en_US |
dc.type | Thesis | en_US |
dc.description.thesisdegreename | PhD | en_US |
dc.description.thesisdegreediscipline | Epidemiological Science | en_US |
dc.description.thesisdegreegrantor | University of Michigan, Horace H. Rackham School of Graduate Studies | en_US |
dc.contributor.committeemember | Foxman, Betsy | en_US |
dc.contributor.committeemember | Zoellner, Sebastian K. | en_US |
dc.contributor.committeemember | Zhang, Lixin | en_US |
dc.contributor.committeemember | Srinivasan, Usha | en_US |
dc.contributor.committeemember | Misra, Dawn P. | en_US |
dc.contributor.committeemember | Marrs, Carl F. | en_US |
dc.subject.hlbsecondlevel | Public Health | en_US |
dc.subject.hlbtoplevel | Health Sciences | en_US |
dc.description.bitstreamurl | http://deepblue.lib.umich.edu/bitstream/2027.42/94083/1/dndtrang_1.pdf | |
dc.owningcollname | Dissertations and Theses (Ph.D. and Master's) |
Files in this item
Remediation of Harmful Language
The University of Michigan Library aims to describe library materials in a way that respects the people and communities who create, use, and are represented in our collections. Report harmful or offensive language in catalog records, finding aids, or elsewhere in our collections anonymously through our metadata feedback form. More information at Remediation of Harmful Language.
Accessibility
If you are unable to use this file in its current format, please select the Contact Us link and we can modify it to make it more accessible to you.