Investigating the biological properties of tigecycline

Quinn, Ryan Francis (2012) Investigating the biological properties of tigecycline. MSc(R) thesis, University of Glasgow.

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Antibiotic resistance of many bacterial strains to current antibiotic treatment strategies are increasing. Bacterial biofilm related diseases displaying resistance to current antibiotics is an area of intense investigations. Failure to eradicate biofilm forming pathogenic microorganisms, coupled with an exacerbated host immune response results in extensive tissue damage and ultimately chronic inflammation within infected patients. Periodontitis and cystic fibrosis (CF) represent typical forms of chronic inflammatory disease

The aim of this study was to evaluate the efficacy of a newly developed glycylcycline, tigecycline, against non-pseudomonal Gram-negative CF pathogens and oral pathogens commonly associated with inflammatory disease of the lung and oral cavity, respectively. Minimum inhibitory concentrations (MICs) of periodontal and pulmonary pathogens in planktonic growth phase and sessile biofilms were determined by serial doubling dilutions with tigecycline. Furthermore, planktonic MICs and sessile MICs exposed to tigecycline and a competitive efflux pump inhibitor MC-207,110 EPI were assessed by XTT assays. In addition the biomasses of sessile biofilms exposed to tigecycline and EPI were determined by crystal violet assay. This investigation demonstrated a significant improvement in the susceptibility of both planktonic and sessile cells to tigecycline following the addition of an EPI, indicating that the EPI enhanced sensitivity to antibiotic treatment of resistant bacterial strains. Furthermore, bacterial biofilm biomass of the CF pathogen Burkholderia cepacia was reduced significantly by co treatments of tigecycline and EPI.

Finally, the immunomodulatory properties of tigecycline were evaluated using clinically relevant epithelial cell lines, A549 OKF6-TERT2 and a primary neutrophil cell line. Oral and pulmonary cell lines were co-inoculated with subinhibitory concentration of tigecycline and Escherichia coli derived lipopolysaccharide (LPS). The neutrophil cell line was co-inoculated with (phorbol 12-myristate acetate) PMA and tigecycline. Epithelial IL-6 and IL-8 levels were determined by ELISA and RT-qPCR, demonstrating only marginal down-regulation in some cases of these inflammatory mediators. However, tigecycline at subinhibitory concentrations did reduce the levels of IL-8 and MMP-9 synthesised by neutrophils in a dose dependent manner.

In conclusion, tigecycline alone is ineffective at killing and reducing biomass of mature biofilms associated with chronic inflammatory disease of the lungs and oral cavity, however the addition of a competitive efflux pump inhibitor decreased resistance of the bacterial biofilm to tigecycline. This would suggest a possible new chemotherapeutic use to treat patients who suffer from a chronic inflammatory disease. Furthermore, down-regulation of inflammatory mediators by subinhibitory concentration of tigecycline may indicate a potential use in the therapeutic management of both CF and periodontal disease, and other diseases of chronic inflammatory origin.

Item Type: Thesis (MSc(R))
Qualification Level: Masters
Keywords: Tigecycline, infammation, periodontal disease, cystic fibrois
Subjects: Q Science > QR Microbiology > QR180 Immunology
Q Science > QR Microbiology
Colleges/Schools: College of Medical Veterinary and Life Sciences > School of Infection & Immunity
Supervisor's Name: Murray, Dr. Colin and Ramage, Dr. Gordon
Date of Award: 2012
Depositing User: Mr Ryan Quinn
Unique ID: glathesis:2012-3144
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 09 Feb 2012
Last Modified: 10 Dec 2012 14:04

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