Introduction: Acanthamoeba keratitis (AK) infection needs to be diagnosed definitively to optimize therapy in order to avoid possible visual impairment.
Aims: 1) To optimize two noted Real-time PCR (RT-PCR) TaqMan methods (Rivière and Qvarnstrom) using the Cepheid SmartCycler® II system. 2) To identify potential inhibitory effects from topical drugs on RT-PCR. 3) To validate and compare the two assays using ocular clinical samples.
Methods: 1) Primers and probes were optimized for both assays to detect genus-specific Acanthamoeba 18S rDNA. 2) Thirteen topical ophthalmic drugs were diluted to determine the level of inhibitory effect present. The lowest non-inhibitory concentrations were then used to determine RT-PCR amplification efficiency. 3) Excess clinical samples (139) were processed for culture and assayed by both assays on the SmartCycler® II and the results were compared.
Results: 1) The Rivière RT-PCR plasmid DNA, cyst and trophozoite limits of detection and amplification efficiency were 10.13 copies/10μl, 0.7/300µl, 2.3/300µl, 94% respectively. The Qvarnstrom RT-PCR plasmid DNA, cyst and trophozoite limits of detection and amplification efficiency were 43.8 copies/10μl, 0.7/300µl, 2.3/300µl, 92% respectively. 2) Out of the thirteen topical drugs, the most noteworthy result was that of Polyhexamethylene biguanide (PHMB). The non-inhibitory dilution and RT-PCR efficiency were 1/2560 and 72.7%. 3) The results of the clinical validation indicated that 134/139 (96.4%) results correlated between the two assays of which 4/134 samples were culture negative but RT-PCR positive.
Conclusions: The two RT-PCR assays were optimized successfully on the SmartCycler® II system with comparable results in detecting genus - specific Acanthamoeba DNA. In examining the effects of thirteen topical drugs on RT-PCR, PHMB was demonstrated to both inhibit the reaction at a high dilution and reduce amplification efficiency substantially. Ocular samples (139) were tested using both assays and results thus far indicate that both could be used to diagnose AK in the laboratory.
Public health relevance: RT-PCR can be used to rapidly diagnose AK. Commencement of AK specific therapy earlier will substantially reduce the patients the pain and suffering. Also by examining the effects of topical ophthalmic drugs on RT-PCR, the potential for false negative results and result delays could be minimized.
| Identifer | oai:union.ndltd.org:PITT/oai:PITTETD:etd-09012007-110049 |
| Date | 27 September 2007 |
| Creators | Thompson, Paul P |
| Contributors | Jeremy Martinson, Robert Wadowsky, Paul Kinchington, Velpandi Ayyavoo, Regis P Kowalski |
| Publisher | University of Pittsburgh |
| Source Sets | University of Pittsburgh |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.library.pitt.edu/ETD/available/etd-09012007-110049/ |
| Rights | restricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to University of Pittsburgh or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
Page generated in 0.002 seconds