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Journal of Clinical Microbiology, December 2002, p. 4428-4434, Vol. 40, No. 12
0095-1137/02/$04.00+0     DOI: 10.1128/JCM.40.12.4428-4434.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

Reliability of Nested PCR for Detection of Chlamydia pneumoniae DNA in Atheromas: Results from a Multicenter Study Applying Standardized Protocols

Petra Apfalter,1* Ojan Assadian,2 Francesco Blasi,3 Jens Boman,4 Charlotte A. Gaydos,5 Michael Kundi,6 Athanasios Makristathis,1 Marion Nehr,1 Manfred L. Rotter,1 and Alexander M. Hirschl1

Division of Clinical Microbiology,1 Division of Hospital Hygiene, Hygiene-Institute,2 Department of Occupational and Social Hygiene, Institute of Environmental Health, University of Vienna, Vienna, Austria,6 Institute of Respiratory Diseases, University of Milan, IRCCS Policlinico, Milan, Italy,3 Department of Clinical Virology, Umeå University Hospital, Umeå, Sweden,4 Department of Medicine, Division of Infectious Diseases, The Johns Hopkins University, Baltimore, Maryland5

Received 7 March 2002/ Returned for modification 13 July 2002/ Accepted 12 August 2002

The present multicenter study was designed to find explanations for the discrepancies in the reported rates of detection of Chlamydia pneumoniae DNA in endarterectomy specimens. Coded identical sets of (i) a C. pneumoniae DNA dilution series (panel 1; n = 10), (ii) spiked control tissue specimens (panel 2; n = 10 specimens, including 5 negative controls), and (iii) endarterectomy specimens (panel 3; 15 atheromas, 5 negative controls) were analyzed at four laboratories by three standardized DNA extraction methods in each laboratory and a nested touchdown PCR protocol targeting the ompA gene of C. pneumoniae. Panel 1 samples were correctly identified as positive to levels of 0.3 inclusion-forming units (IFU)/PCR mixture (100%) and 0.03 IFU/PCR mixture (50%). All negative controls were correctly reported as negative. Panel 2 samples were identified as C. pneumoniae positive to levels of 0.01 IFU/PCR mixture (100%) and 0.005 IFU/PCR mixture (91%), independent of the DNA extraction method used, and only one false-positive result was reported. For panel 3 samples, 5 of 240 (2%) analyses (in which DNA extractions and PCR were performed at the same laboratory) were positive; the positive specimens were from three endarterectomy specimens and two negative controls. After exchange of DNA extracts between laboratories, 13 of 15 atheroma samples were C. pneumoniae DNA positive in at least 1 of a series of 48 analyses per atheroma sample; however, the overall positivity rate did not exceed 5% (33 of 720 analyses) and therefore was lower than that for the negative controls (8%; 19 of 240 analyses). Not a single positive result could be achieved when all panel 3 extracts (n = 240 analyses) were reamplified by a 16S rRNA PCR followed by hybridization with a C. pneumoniae-specific probe. Statistical analyses demonstrated that positive results did not occur in an independent and random fashion and could most likely be explained by amplicon carryover at the nested PCR level as well as amplicon introduction during DNA extraction, but not by the patterns of distribution of very low target levels or a certain DNA extraction protocol. The results of studies by nested PCR for detection of the prevalence of C. pneumoniae will always be questionable.


* Corresponding author. Mailing address: Department of Clinical Microbiology, Hygiene-Institute, University of Vienna, Vienna University Hospital, Währinger Gürtel 18-20/5P, A-1090 Vienna, Austria, Phone: 43 (1) 40400-5151. Fax: 43 (1) 40400-5228. E-mail: Petra.Apfalter{at}akh-wien.ac.at.


Journal of Clinical Microbiology, December 2002, p. 4428-4434, Vol. 40, No. 12
0095-1137/02/$04.00+0     DOI: 10.1128/JCM.40.12.4428-4434.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.




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